Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

17 files changed, 3831 insertions, 0 deletions

diff --git a/third_party/python/attrs/attr/__init__.py b/third_party/python/attrs/attr/__init__.py
new file mode 100644
index 0000000000..66ce10920b
--- /dev/null
+++ b/third_party/python/attrs/attr/__init__.py
@@ -0,0 +1,68 @@
+from __future__ import absolute_import, division, print_function
+
+from functools import partial
+
+from . import converters, exceptions, filters, validators
+from ._config import get_run_validators, set_run_validators
+from ._funcs import asdict, assoc, astuple, evolve, has
+from ._make import (
+    NOTHING,
+    Attribute,
+    Factory,
+    attrib,
+    attrs,
+    fields,
+    fields_dict,
+    make_class,
+    validate,
+)
+from ._version import VersionInfo
+
+
+__version__ = "19.2.0"
+__version_info__ = VersionInfo._from_version_string(__version__)
+
+__title__ = "attrs"
+__description__ = "Classes Without Boilerplate"
+__url__ = "https://www.attrs.org/"
+__uri__ = __url__
+__doc__ = __description__ + " <" + __uri__ + ">"
+
+__author__ = "Hynek Schlawack"
+__email__ = "hs@ox.cx"
+
+__license__ = "MIT"
+__copyright__ = "Copyright (c) 2015 Hynek Schlawack"
+
+
+s = attributes = attrs
+ib = attr = attrib
+dataclass = partial(attrs, auto_attribs=True)  # happy Easter ;)
+
+
+__all__ = [
+    "Attribute",
+    "Factory",
+    "NOTHING",
+    "asdict",
+    "assoc",
+    "astuple",
+    "attr",
+    "attrib",
+    "attributes",
+    "attrs",
+    "converters",
+    "evolve",
+    "exceptions",
+    "fields",
+    "fields_dict",
+    "filters",
+    "get_run_validators",
+    "has",
+    "ib",
+    "make_class",
+    "s",
+    "set_run_validators",
+    "validate",
+    "validators",
+]
diff --git a/third_party/python/attrs/attr/__init__.pyi b/third_party/python/attrs/attr/__init__.pyi
new file mode 100644
index 0000000000..d19a055466
--- /dev/null
+++ b/third_party/python/attrs/attr/__init__.pyi
@@ -0,0 +1,278 @@
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Generic,
+    List,
+    Optional,
+    Sequence,
+    Mapping,
+    Tuple,
+    Type,
+    TypeVar,
+    Union,
+    overload,
+)
+
+# `import X as X` is required to make these public
+from . import exceptions as exceptions
+from . import filters as filters
+from . import converters as converters
+from . import validators as validators
+
+from ._version import VersionInfo
+
+__version__: str
+__version_info__: VersionInfo
+__title__: str
+__description__: str
+__url__: str
+__uri__: str
+__author__: str
+__email__: str
+__license__: str
+__copyright__: str
+
+_T = TypeVar("_T")
+_C = TypeVar("_C", bound=type)
+
+_ValidatorType = Callable[[Any, Attribute[_T], _T], Any]
+_ConverterType = Callable[[Any], _T]
+_FilterType = Callable[[Attribute[_T], _T], bool]
+_ReprType = Callable[[Any], str]
+_ReprArgType = Union[bool, _ReprType]
+# FIXME: in reality, if multiple validators are passed they must be in a list or tuple,
+# but those are invariant and so would prevent subtypes of _ValidatorType from working
+# when passed in a list or tuple.
+_ValidatorArgType = Union[_ValidatorType[_T], Sequence[_ValidatorType[_T]]]
+
+# _make --
+
+NOTHING: object
+
+# NOTE: Factory lies about its return type to make this possible: `x: List[int] = Factory(list)`
+# Work around mypy issue #4554 in the common case by using an overload.
+@overload
+def Factory(factory: Callable[[], _T]) -> _T: ...
+@overload
+def Factory(
+    factory: Union[Callable[[Any], _T], Callable[[], _T]],
+    takes_self: bool = ...,
+) -> _T: ...
+
+class Attribute(Generic[_T]):
+    name: str
+    default: Optional[_T]
+    validator: Optional[_ValidatorType[_T]]
+    repr: _ReprArgType
+    cmp: bool
+    eq: bool
+    order: bool
+    hash: Optional[bool]
+    init: bool
+    converter: Optional[_ConverterType[_T]]
+    metadata: Dict[Any, Any]
+    type: Optional[Type[_T]]
+    kw_only: bool
+
+# NOTE: We had several choices for the annotation to use for type arg:
+# 1) Type[_T]
+#   - Pros: Handles simple cases correctly
+#   - Cons: Might produce less informative errors in the case of conflicting TypeVars
+#   e.g. `attr.ib(default='bad', type=int)`
+# 2) Callable[..., _T]
+#   - Pros: Better error messages than #1 for conflicting TypeVars
+#   - Cons: Terrible error messages for validator checks.
+#   e.g. attr.ib(type=int, validator=validate_str)
+#        -> error: Cannot infer function type argument
+# 3) type (and do all of the work in the mypy plugin)
+#   - Pros: Simple here, and we could customize the plugin with our own errors.
+#   - Cons: Would need to write mypy plugin code to handle all the cases.
+# We chose option #1.
+
+# `attr` lies about its return type to make the following possible:
+#     attr()    -> Any
+#     attr(8)   -> int
+#     attr(validator=<some callable>)  -> Whatever the callable expects.
+# This makes this type of assignments possible:
+#     x: int = attr(8)
+#
+# This form catches explicit None or no default but with no other arguments returns Any.
+@overload
+def attrib(
+    default: None = ...,
+    validator: None = ...,
+    repr: _ReprArgType = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    metadata: Optional[Mapping[Any, Any]] = ...,
+    type: None = ...,
+    converter: None = ...,
+    factory: None = ...,
+    kw_only: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> Any: ...
+
+# This form catches an explicit None or no default and infers the type from the other arguments.
+@overload
+def attrib(
+    default: None = ...,
+    validator: Optional[_ValidatorArgType[_T]] = ...,
+    repr: _ReprArgType = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    metadata: Optional[Mapping[Any, Any]] = ...,
+    type: Optional[Type[_T]] = ...,
+    converter: Optional[_ConverterType[_T]] = ...,
+    factory: Optional[Callable[[], _T]] = ...,
+    kw_only: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> _T: ...
+
+# This form catches an explicit default argument.
+@overload
+def attrib(
+    default: _T,
+    validator: Optional[_ValidatorArgType[_T]] = ...,
+    repr: _ReprArgType = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    metadata: Optional[Mapping[Any, Any]] = ...,
+    type: Optional[Type[_T]] = ...,
+    converter: Optional[_ConverterType[_T]] = ...,
+    factory: Optional[Callable[[], _T]] = ...,
+    kw_only: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> _T: ...
+
+# This form covers type=non-Type: e.g. forward references (str), Any
+@overload
+def attrib(
+    default: Optional[_T] = ...,
+    validator: Optional[_ValidatorArgType[_T]] = ...,
+    repr: _ReprArgType = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    metadata: Optional[Mapping[Any, Any]] = ...,
+    type: object = ...,
+    converter: Optional[_ConverterType[_T]] = ...,
+    factory: Optional[Callable[[], _T]] = ...,
+    kw_only: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> Any: ...
+@overload
+def attrs(
+    maybe_cls: _C,
+    these: Optional[Dict[str, Any]] = ...,
+    repr_ns: Optional[str] = ...,
+    repr: bool = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    slots: bool = ...,
+    frozen: bool = ...,
+    weakref_slot: bool = ...,
+    str: bool = ...,
+    auto_attribs: bool = ...,
+    kw_only: bool = ...,
+    cache_hash: bool = ...,
+    auto_exc: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> _C: ...
+@overload
+def attrs(
+    maybe_cls: None = ...,
+    these: Optional[Dict[str, Any]] = ...,
+    repr_ns: Optional[str] = ...,
+    repr: bool = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    slots: bool = ...,
+    frozen: bool = ...,
+    weakref_slot: bool = ...,
+    str: bool = ...,
+    auto_attribs: bool = ...,
+    kw_only: bool = ...,
+    cache_hash: bool = ...,
+    auto_exc: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> Callable[[_C], _C]: ...
+
+# TODO: add support for returning NamedTuple from the mypy plugin
+class _Fields(Tuple[Attribute[Any], ...]):
+    def __getattr__(self, name: str) -> Attribute[Any]: ...
+
+def fields(cls: type) -> _Fields: ...
+def fields_dict(cls: type) -> Dict[str, Attribute[Any]]: ...
+def validate(inst: Any) -> None: ...
+
+# TODO: add support for returning a proper attrs class from the mypy plugin
+# we use Any instead of _CountingAttr so that e.g. `make_class('Foo', [attr.ib()])` is valid
+def make_class(
+    name: str,
+    attrs: Union[List[str], Tuple[str, ...], Dict[str, Any]],
+    bases: Tuple[type, ...] = ...,
+    repr_ns: Optional[str] = ...,
+    repr: bool = ...,
+    cmp: Optional[bool] = ...,
+    hash: Optional[bool] = ...,
+    init: bool = ...,
+    slots: bool = ...,
+    frozen: bool = ...,
+    weakref_slot: bool = ...,
+    str: bool = ...,
+    auto_attribs: bool = ...,
+    kw_only: bool = ...,
+    cache_hash: bool = ...,
+    auto_exc: bool = ...,
+    eq: Optional[bool] = ...,
+    order: Optional[bool] = ...,
+) -> type: ...
+
+# _funcs --
+
+# TODO: add support for returning TypedDict from the mypy plugin
+# FIXME: asdict/astuple do not honor their factory args.  waiting on one of these:
+# https://github.com/python/mypy/issues/4236
+# https://github.com/python/typing/issues/253
+def asdict(
+    inst: Any,
+    recurse: bool = ...,
+    filter: Optional[_FilterType[Any]] = ...,
+    dict_factory: Type[Mapping[Any, Any]] = ...,
+    retain_collection_types: bool = ...,
+) -> Dict[str, Any]: ...
+
+# TODO: add support for returning NamedTuple from the mypy plugin
+def astuple(
+    inst: Any,
+    recurse: bool = ...,
+    filter: Optional[_FilterType[Any]] = ...,
+    tuple_factory: Type[Sequence[Any]] = ...,
+    retain_collection_types: bool = ...,
+) -> Tuple[Any, ...]: ...
+def has(cls: type) -> bool: ...
+def assoc(inst: _T, **changes: Any) -> _T: ...
+def evolve(inst: _T, **changes: Any) -> _T: ...
+
+# _config --
+
+def set_run_validators(run: bool) -> None: ...
+def get_run_validators() -> bool: ...
+
+# aliases --
+
+s = attributes = attrs
+ib = attr = attrib
+dataclass = attrs  # Technically, partial(attrs, auto_attribs=True) ;)
diff --git a/third_party/python/attrs/attr/_compat.py b/third_party/python/attrs/attr/_compat.py
new file mode 100644
index 0000000000..a915db8ebe
--- /dev/null
+++ b/third_party/python/attrs/attr/_compat.py
@@ -0,0 +1,230 @@
+from __future__ import absolute_import, division, print_function
+
+import platform
+import sys
+import types
+import warnings
+
+
+PY2 = sys.version_info[0] == 2
+PYPY = platform.python_implementation() == "PyPy"
+
+
+if PYPY or sys.version_info[:2] >= (3, 6):
+    ordered_dict = dict
+else:
+    from collections import OrderedDict
+
+    ordered_dict = OrderedDict
+
+
+if PY2:
+    from UserDict import IterableUserDict
+    from collections import Mapping, Sequence
+
+    # We 'bundle' isclass instead of using inspect as importing inspect is
+    # fairly expensive (order of 10-15 ms for a modern machine in 2016)
+    def isclass(klass):
+        return isinstance(klass, (type, types.ClassType))
+
+    # TYPE is used in exceptions, repr(int) is different on Python 2 and 3.
+    TYPE = "type"
+
+    def iteritems(d):
+        return d.iteritems()
+
+    # Python 2 is bereft of a read-only dict proxy, so we make one!
+    class ReadOnlyDict(IterableUserDict):
+        """
+        Best-effort read-only dict wrapper.
+        """
+
+        def __setitem__(self, key, val):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise TypeError(
+                "'mappingproxy' object does not support item assignment"
+            )
+
+        def update(self, _):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError(
+                "'mappingproxy' object has no attribute 'update'"
+            )
+
+        def __delitem__(self, _):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise TypeError(
+                "'mappingproxy' object does not support item deletion"
+            )
+
+        def clear(self):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError(
+                "'mappingproxy' object has no attribute 'clear'"
+            )
+
+        def pop(self, key, default=None):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError(
+                "'mappingproxy' object has no attribute 'pop'"
+            )
+
+        def popitem(self):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError(
+                "'mappingproxy' object has no attribute 'popitem'"
+            )
+
+        def setdefault(self, key, default=None):
+            # We gently pretend we're a Python 3 mappingproxy.
+            raise AttributeError(
+                "'mappingproxy' object has no attribute 'setdefault'"
+            )
+
+        def __repr__(self):
+            # Override to be identical to the Python 3 version.
+            return "mappingproxy(" + repr(self.data) + ")"
+
+    def metadata_proxy(d):
+        res = ReadOnlyDict()
+        res.data.update(d)  # We blocked update, so we have to do it like this.
+        return res
+
+    def just_warn(*args, **kw):  # pragma: nocover
+        """
+        We only warn on Python 3 because we are not aware of any concrete
+        consequences of not setting the cell on Python 2.
+        """
+
+
+else:  # Python 3 and later.
+    from collections.abc import Mapping, Sequence  # noqa
+
+    def just_warn(*args, **kw):
+        """
+        We only warn on Python 3 because we are not aware of any concrete
+        consequences of not setting the cell on Python 2.
+        """
+        warnings.warn(
+            "Running interpreter doesn't sufficiently support code object "
+            "introspection.  Some features like bare super() or accessing "
+            "__class__ will not work with slotted classes.",
+            RuntimeWarning,
+            stacklevel=2,
+        )
+
+    def isclass(klass):
+        return isinstance(klass, type)
+
+    TYPE = "class"
+
+    def iteritems(d):
+        return d.items()
+
+    def metadata_proxy(d):
+        return types.MappingProxyType(dict(d))
+
+
+def make_set_closure_cell():
+    """Return a function of two arguments (cell, value) which sets
+    the value stored in the closure cell `cell` to `value`.
+    """
+    # pypy makes this easy. (It also supports the logic below, but
+    # why not do the easy/fast thing?)
+    if PYPY:  # pragma: no cover
+
+        def set_closure_cell(cell, value):
+            cell.__setstate__((value,))
+
+        return set_closure_cell
+
+    # Otherwise gotta do it the hard way.
+
+    # Create a function that will set its first cellvar to `value`.
+    def set_first_cellvar_to(value):
+        x = value
+        return
+
+        # This function will be eliminated as dead code, but
+        # not before its reference to `x` forces `x` to be
+        # represented as a closure cell rather than a local.
+        def force_x_to_be_a_cell():  # pragma: no cover
+            return x
+
+    try:
+        # Extract the code object and make sure our assumptions about
+        # the closure behavior are correct.
+        if PY2:
+            co = set_first_cellvar_to.func_code
+        else:
+            co = set_first_cellvar_to.__code__
+        if co.co_cellvars != ("x",) or co.co_freevars != ():
+            raise AssertionError  # pragma: no cover
+
+        # Convert this code object to a code object that sets the
+        # function's first _freevar_ (not cellvar) to the argument.
+        if sys.version_info >= (3, 8):
+            # CPython 3.8+ has an incompatible CodeType signature
+            # (added a posonlyargcount argument) but also added
+            # CodeType.replace() to do this without counting parameters.
+            set_first_freevar_code = co.replace(
+                co_cellvars=co.co_freevars, co_freevars=co.co_cellvars
+            )
+        else:
+            args = [co.co_argcount]
+            if not PY2:
+                args.append(co.co_kwonlyargcount)
+            args.extend(
+                [
+                    co.co_nlocals,
+                    co.co_stacksize,
+                    co.co_flags,
+                    co.co_code,
+                    co.co_consts,
+                    co.co_names,
+                    co.co_varnames,
+                    co.co_filename,
+                    co.co_name,
+                    co.co_firstlineno,
+                    co.co_lnotab,
+                    # These two arguments are reversed:
+                    co.co_cellvars,
+                    co.co_freevars,
+                ]
+            )
+            set_first_freevar_code = types.CodeType(*args)
+
+        def set_closure_cell(cell, value):
+            # Create a function using the set_first_freevar_code,
+            # whose first closure cell is `cell`. Calling it will
+            # change the value of that cell.
+            setter = types.FunctionType(
+                set_first_freevar_code, {}, "setter", (), (cell,)
+            )
+            # And call it to set the cell.
+            setter(value)
+
+        # Make sure it works on this interpreter:
+        def make_func_with_cell():
+            x = None
+
+            def func():
+                return x  # pragma: no cover
+
+            return func
+
+        if PY2:
+            cell = make_func_with_cell().func_closure[0]
+        else:
+            cell = make_func_with_cell().__closure__[0]
+        set_closure_cell(cell, 100)
+        if cell.cell_contents != 100:
+            raise AssertionError  # pragma: no cover
+
+    except Exception:
+        return just_warn
+    else:
+        return set_closure_cell
+
+
+set_closure_cell = make_set_closure_cell()
diff --git a/third_party/python/attrs/attr/_config.py b/third_party/python/attrs/attr/_config.py
new file mode 100644
index 0000000000..8ec920962d
--- /dev/null
+++ b/third_party/python/attrs/attr/_config.py
@@ -0,0 +1,23 @@
+from __future__ import absolute_import, division, print_function
+
+
+__all__ = ["set_run_validators", "get_run_validators"]
+
+_run_validators = True
+
+
+def set_run_validators(run):
+    """
+    Set whether or not validators are run.  By default, they are run.
+    """
+    if not isinstance(run, bool):
+        raise TypeError("'run' must be bool.")
+    global _run_validators
+    _run_validators = run
+
+
+def get_run_validators():
+    """
+    Return whether or not validators are run.
+    """
+    return _run_validators
diff --git a/third_party/python/attrs/attr/_funcs.py b/third_party/python/attrs/attr/_funcs.py
new file mode 100644
index 0000000000..c077e4284f
--- /dev/null
+++ b/third_party/python/attrs/attr/_funcs.py
@@ -0,0 +1,290 @@
+from __future__ import absolute_import, division, print_function
+
+import copy
+
+from ._compat import iteritems
+from ._make import NOTHING, _obj_setattr, fields
+from .exceptions import AttrsAttributeNotFoundError
+
+
+def asdict(
+    inst,
+    recurse=True,
+    filter=None,
+    dict_factory=dict,
+    retain_collection_types=False,
+):
+    """
+    Return the ``attrs`` attribute values of *inst* as a dict.
+
+    Optionally recurse into other ``attrs``-decorated classes.
+
+    :param inst: Instance of an ``attrs``-decorated class.
+    :param bool recurse: Recurse into classes that are also
+        ``attrs``-decorated.
+    :param callable filter: A callable whose return code determines whether an
+        attribute or element is included (``True``) or dropped (``False``).  Is
+        called with the `attr.Attribute` as the first argument and the
+        value as the second argument.
+    :param callable dict_factory: A callable to produce dictionaries from.  For
+        example, to produce ordered dictionaries instead of normal Python
+        dictionaries, pass in ``collections.OrderedDict``.
+    :param bool retain_collection_types: Do not convert to ``list`` when
+        encountering an attribute whose type is ``tuple`` or ``set``.  Only
+        meaningful if ``recurse`` is ``True``.
+
+    :rtype: return type of *dict_factory*
+
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  versionadded:: 16.0.0 *dict_factory*
+    ..  versionadded:: 16.1.0 *retain_collection_types*
+    """
+    attrs = fields(inst.__class__)
+    rv = dict_factory()
+    for a in attrs:
+        v = getattr(inst, a.name)
+        if filter is not None and not filter(a, v):
+            continue
+        if recurse is True:
+            if has(v.__class__):
+                rv[a.name] = asdict(
+                    v, True, filter, dict_factory, retain_collection_types
+                )
+            elif isinstance(v, (tuple, list, set)):
+                cf = v.__class__ if retain_collection_types is True else list
+                rv[a.name] = cf(
+                    [
+                        _asdict_anything(
+                            i, filter, dict_factory, retain_collection_types
+                        )
+                        for i in v
+                    ]
+                )
+            elif isinstance(v, dict):
+                df = dict_factory
+                rv[a.name] = df(
+                    (
+                        _asdict_anything(
+                            kk, filter, df, retain_collection_types
+                        ),
+                        _asdict_anything(
+                            vv, filter, df, retain_collection_types
+                        ),
+                    )
+                    for kk, vv in iteritems(v)
+                )
+            else:
+                rv[a.name] = v
+        else:
+            rv[a.name] = v
+    return rv
+
+
+def _asdict_anything(val, filter, dict_factory, retain_collection_types):
+    """
+    ``asdict`` only works on attrs instances, this works on anything.
+    """
+    if getattr(val.__class__, "__attrs_attrs__", None) is not None:
+        # Attrs class.
+        rv = asdict(val, True, filter, dict_factory, retain_collection_types)
+    elif isinstance(val, (tuple, list, set)):
+        cf = val.__class__ if retain_collection_types is True else list
+        rv = cf(
+            [
+                _asdict_anything(
+                    i, filter, dict_factory, retain_collection_types
+                )
+                for i in val
+            ]
+        )
+    elif isinstance(val, dict):
+        df = dict_factory
+        rv = df(
+            (
+                _asdict_anything(kk, filter, df, retain_collection_types),
+                _asdict_anything(vv, filter, df, retain_collection_types),
+            )
+            for kk, vv in iteritems(val)
+        )
+    else:
+        rv = val
+    return rv
+
+
+def astuple(
+    inst,
+    recurse=True,
+    filter=None,
+    tuple_factory=tuple,
+    retain_collection_types=False,
+):
+    """
+    Return the ``attrs`` attribute values of *inst* as a tuple.
+
+    Optionally recurse into other ``attrs``-decorated classes.
+
+    :param inst: Instance of an ``attrs``-decorated class.
+    :param bool recurse: Recurse into classes that are also
+        ``attrs``-decorated.
+    :param callable filter: A callable whose return code determines whether an
+        attribute or element is included (``True``) or dropped (``False``).  Is
+        called with the `attr.Attribute` as the first argument and the
+        value as the second argument.
+    :param callable tuple_factory: A callable to produce tuples from.  For
+        example, to produce lists instead of tuples.
+    :param bool retain_collection_types: Do not convert to ``list``
+        or ``dict`` when encountering an attribute which type is
+        ``tuple``, ``dict`` or ``set``.  Only meaningful if ``recurse`` is
+        ``True``.
+
+    :rtype: return type of *tuple_factory*
+
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  versionadded:: 16.2.0
+    """
+    attrs = fields(inst.__class__)
+    rv = []
+    retain = retain_collection_types  # Very long. :/
+    for a in attrs:
+        v = getattr(inst, a.name)
+        if filter is not None and not filter(a, v):
+            continue
+        if recurse is True:
+            if has(v.__class__):
+                rv.append(
+                    astuple(
+                        v,
+                        recurse=True,
+                        filter=filter,
+                        tuple_factory=tuple_factory,
+                        retain_collection_types=retain,
+                    )
+                )
+            elif isinstance(v, (tuple, list, set)):
+                cf = v.__class__ if retain is True else list
+                rv.append(
+                    cf(
+                        [
+                            astuple(
+                                j,
+                                recurse=True,
+                                filter=filter,
+                                tuple_factory=tuple_factory,
+                                retain_collection_types=retain,
+                            )
+                            if has(j.__class__)
+                            else j
+                            for j in v
+                        ]
+                    )
+                )
+            elif isinstance(v, dict):
+                df = v.__class__ if retain is True else dict
+                rv.append(
+                    df(
+                        (
+                            astuple(
+                                kk,
+                                tuple_factory=tuple_factory,
+                                retain_collection_types=retain,
+                            )
+                            if has(kk.__class__)
+                            else kk,
+                            astuple(
+                                vv,
+                                tuple_factory=tuple_factory,
+                                retain_collection_types=retain,
+                            )
+                            if has(vv.__class__)
+                            else vv,
+                        )
+                        for kk, vv in iteritems(v)
+                    )
+                )
+            else:
+                rv.append(v)
+        else:
+            rv.append(v)
+    return rv if tuple_factory is list else tuple_factory(rv)
+
+
+def has(cls):
+    """
+    Check whether *cls* is a class with ``attrs`` attributes.
+
+    :param type cls: Class to introspect.
+    :raise TypeError: If *cls* is not a class.
+
+    :rtype: bool
+    """
+    return getattr(cls, "__attrs_attrs__", None) is not None
+
+
+def assoc(inst, **changes):
+    """
+    Copy *inst* and apply *changes*.
+
+    :param inst: Instance of a class with ``attrs`` attributes.
+    :param changes: Keyword changes in the new copy.
+
+    :return: A copy of inst with *changes* incorporated.
+
+    :raise attr.exceptions.AttrsAttributeNotFoundError: If *attr_name* couldn't
+        be found on *cls*.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  deprecated:: 17.1.0
+        Use `evolve` instead.
+    """
+    import warnings
+
+    warnings.warn(
+        "assoc is deprecated and will be removed after 2018/01.",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+    new = copy.copy(inst)
+    attrs = fields(inst.__class__)
+    for k, v in iteritems(changes):
+        a = getattr(attrs, k, NOTHING)
+        if a is NOTHING:
+            raise AttrsAttributeNotFoundError(
+                "{k} is not an attrs attribute on {cl}.".format(
+                    k=k, cl=new.__class__
+                )
+            )
+        _obj_setattr(new, k, v)
+    return new
+
+
+def evolve(inst, **changes):
+    """
+    Create a new instance, based on *inst* with *changes* applied.
+
+    :param inst: Instance of a class with ``attrs`` attributes.
+    :param changes: Keyword changes in the new copy.
+
+    :return: A copy of inst with *changes* incorporated.
+
+    :raise TypeError: If *attr_name* couldn't be found in the class
+        ``__init__``.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    ..  versionadded:: 17.1.0
+    """
+    cls = inst.__class__
+    attrs = fields(cls)
+    for a in attrs:
+        if not a.init:
+            continue
+        attr_name = a.name  # To deal with private attributes.
+        init_name = attr_name if attr_name[0] != "_" else attr_name[1:]
+        if init_name not in changes:
+            changes[init_name] = getattr(inst, attr_name)
+    return cls(**changes)
diff --git a/third_party/python/attrs/attr/_make.py b/third_party/python/attrs/attr/_make.py
new file mode 100644
index 0000000000..5bdd468867
--- /dev/null
+++ b/third_party/python/attrs/attr/_make.py
@@ -0,0 +1,2168 @@
+from __future__ import absolute_import, division, print_function
+
+import copy
+import linecache
+import sys
+import threading
+import uuid
+import warnings
+
+from operator import itemgetter
+
+from . import _config
+from ._compat import (
+    PY2,
+    isclass,
+    iteritems,
+    metadata_proxy,
+    ordered_dict,
+    set_closure_cell,
+)
+from .exceptions import (
+    DefaultAlreadySetError,
+    FrozenInstanceError,
+    NotAnAttrsClassError,
+    PythonTooOldError,
+    UnannotatedAttributeError,
+)
+
+
+# This is used at least twice, so cache it here.
+_obj_setattr = object.__setattr__
+_init_converter_pat = "__attr_converter_{}"
+_init_factory_pat = "__attr_factory_{}"
+_tuple_property_pat = (
+    "    {attr_name} = _attrs_property(_attrs_itemgetter({index}))"
+)
+_classvar_prefixes = ("typing.ClassVar", "t.ClassVar", "ClassVar")
+# we don't use a double-underscore prefix because that triggers
+# name mangling when trying to create a slot for the field
+# (when slots=True)
+_hash_cache_field = "_attrs_cached_hash"
+
+_empty_metadata_singleton = metadata_proxy({})
+
+# Unique object for unequivocal getattr() defaults.
+_sentinel = object()
+
+
+class _Nothing(object):
+    """
+    Sentinel class to indicate the lack of a value when ``None`` is ambiguous.
+
+    ``_Nothing`` is a singleton. There is only ever one of it.
+    """
+
+    _singleton = None
+
+    def __new__(cls):
+        if _Nothing._singleton is None:
+            _Nothing._singleton = super(_Nothing, cls).__new__(cls)
+        return _Nothing._singleton
+
+    def __repr__(self):
+        return "NOTHING"
+
+
+NOTHING = _Nothing()
+"""
+Sentinel to indicate the lack of a value when ``None`` is ambiguous.
+"""
+
+
+def attrib(
+    default=NOTHING,
+    validator=None,
+    repr=True,
+    cmp=None,
+    hash=None,
+    init=True,
+    metadata=None,
+    type=None,
+    converter=None,
+    factory=None,
+    kw_only=False,
+    eq=None,
+    order=None,
+):
+    """
+    Create a new attribute on a class.
+
+    ..  warning::
+
+        Does *not* do anything unless the class is also decorated with
+        `attr.s`!
+
+    :param default: A value that is used if an ``attrs``-generated ``__init__``
+        is used and no value is passed while instantiating or the attribute is
+        excluded using ``init=False``.
+
+        If the value is an instance of `Factory`, its callable will be
+        used to construct a new value (useful for mutable data types like lists
+        or dicts).
+
+        If a default is not set (or set manually to ``attr.NOTHING``), a value
+        *must* be supplied when instantiating; otherwise a `TypeError`
+        will be raised.
+
+        The default can also be set using decorator notation as shown below.
+
+    :type default: Any value
+
+    :param callable factory: Syntactic sugar for
+        ``default=attr.Factory(callable)``.
+
+    :param validator: `callable` that is called by ``attrs``-generated
+        ``__init__`` methods after the instance has been initialized.  They
+        receive the initialized instance, the `Attribute`, and the
+        passed value.
+
+        The return value is *not* inspected so the validator has to throw an
+        exception itself.
+
+        If a ``list`` is passed, its items are treated as validators and must
+        all pass.
+
+        Validators can be globally disabled and re-enabled using
+        `get_run_validators`.
+
+        The validator can also be set using decorator notation as shown below.
+
+    :type validator: ``callable`` or a ``list`` of ``callable``\\ s.
+
+    :param repr: Include this attribute in the generated ``__repr__``
+        method. If ``True``, include the attribute; if ``False``, omit it. By
+        default, the built-in ``repr()`` function is used. To override how the
+        attribute value is formatted, pass a ``callable`` that takes a single
+        value and returns a string. Note that the resulting string is used
+        as-is, i.e. it will be used directly *instead* of calling ``repr()``
+        (the default).
+    :type repr: a ``bool`` or a ``callable`` to use a custom function.
+    :param bool eq: If ``True`` (default), include this attribute in the
+        generated ``__eq__`` and ``__ne__`` methods that check two instances
+        for equality.
+    :param bool order: If ``True`` (default), include this attributes in the
+        generated ``__lt__``, ``__le__``, ``__gt__`` and ``__ge__`` methods.
+    :param bool cmp: Setting to ``True`` is equivalent to setting ``eq=True,
+        order=True``. Deprecated in favor of *eq* and *order*.
+    :param hash: Include this attribute in the generated ``__hash__``
+        method.  If ``None`` (default), mirror *eq*'s value.  This is the
+        correct behavior according the Python spec.  Setting this value to
+        anything else than ``None`` is *discouraged*.
+    :type hash: ``bool`` or ``None``
+    :param bool init: Include this attribute in the generated ``__init__``
+        method.  It is possible to set this to ``False`` and set a default
+        value.  In that case this attributed is unconditionally initialized
+        with the specified default value or factory.
+    :param callable converter: `callable` that is called by
+        ``attrs``-generated ``__init__`` methods to converter attribute's value
+        to the desired format.  It is given the passed-in value, and the
+        returned value will be used as the new value of the attribute.  The
+        value is converted before being passed to the validator, if any.
+    :param metadata: An arbitrary mapping, to be used by third-party
+        components.  See `extending_metadata`.
+    :param type: The type of the attribute.  In Python 3.6 or greater, the
+        preferred method to specify the type is using a variable annotation
+        (see `PEP 526 <https://www.python.org/dev/peps/pep-0526/>`_).
+        This argument is provided for backward compatibility.
+        Regardless of the approach used, the type will be stored on
+        ``Attribute.type``.
+
+        Please note that ``attrs`` doesn't do anything with this metadata by
+        itself. You can use it as part of your own code or for
+        `static type checking <types>`.
+    :param kw_only: Make this attribute keyword-only (Python 3+)
+        in the generated ``__init__`` (if ``init`` is ``False``, this
+        parameter is ignored).
+
+    .. versionadded:: 15.2.0 *convert*
+    .. versionadded:: 16.3.0 *metadata*
+    .. versionchanged:: 17.1.0 *validator* can be a ``list`` now.
+    .. versionchanged:: 17.1.0
+       *hash* is ``None`` and therefore mirrors *eq* by default.
+    .. versionadded:: 17.3.0 *type*
+    .. deprecated:: 17.4.0 *convert*
+    .. versionadded:: 17.4.0 *converter* as a replacement for the deprecated
+       *convert* to achieve consistency with other noun-based arguments.
+    .. versionadded:: 18.1.0
+       ``factory=f`` is syntactic sugar for ``default=attr.Factory(f)``.
+    .. versionadded:: 18.2.0 *kw_only*
+    .. versionchanged:: 19.2.0 *convert* keyword argument removed
+    .. versionchanged:: 19.2.0 *repr* also accepts a custom callable.
+    .. deprecated:: 19.2.0 *cmp* Removal on or after 2021-06-01.
+    .. versionadded:: 19.2.0 *eq* and *order*
+    """
+    eq, order = _determine_eq_order(cmp, eq, order)
+
+    if hash is not None and hash is not True and hash is not False:
+        raise TypeError(
+            "Invalid value for hash.  Must be True, False, or None."
+        )
+
+    if factory is not None:
+        if default is not NOTHING:
+            raise ValueError(
+                "The `default` and `factory` arguments are mutually "
+                "exclusive."
+            )
+        if not callable(factory):
+            raise ValueError("The `factory` argument must be a callable.")
+        default = Factory(factory)
+
+    if metadata is None:
+        metadata = {}
+
+    return _CountingAttr(
+        default=default,
+        validator=validator,
+        repr=repr,
+        cmp=None,
+        hash=hash,
+        init=init,
+        converter=converter,
+        metadata=metadata,
+        type=type,
+        kw_only=kw_only,
+        eq=eq,
+        order=order,
+    )
+
+
+def _make_attr_tuple_class(cls_name, attr_names):
+    """
+    Create a tuple subclass to hold `Attribute`s for an `attrs` class.
+
+    The subclass is a bare tuple with properties for names.
+
+    class MyClassAttributes(tuple):
+        __slots__ = ()
+        x = property(itemgetter(0))
+    """
+    attr_class_name = "{}Attributes".format(cls_name)
+    attr_class_template = [
+        "class {}(tuple):".format(attr_class_name),
+        "    __slots__ = ()",
+    ]
+    if attr_names:
+        for i, attr_name in enumerate(attr_names):
+            attr_class_template.append(
+                _tuple_property_pat.format(index=i, attr_name=attr_name)
+            )
+    else:
+        attr_class_template.append("    pass")
+    globs = {"_attrs_itemgetter": itemgetter, "_attrs_property": property}
+    eval(compile("\n".join(attr_class_template), "", "exec"), globs)
+
+    return globs[attr_class_name]
+
+
+# Tuple class for extracted attributes from a class definition.
+# `base_attrs` is a subset of `attrs`.
+_Attributes = _make_attr_tuple_class(
+    "_Attributes",
+    [
+        # all attributes to build dunder methods for
+        "attrs",
+        # attributes that have been inherited
+        "base_attrs",
+        # map inherited attributes to their originating classes
+        "base_attrs_map",
+    ],
+)
+
+
+def _is_class_var(annot):
+    """
+    Check whether *annot* is a typing.ClassVar.
+
+    The string comparison hack is used to avoid evaluating all string
+    annotations which would put attrs-based classes at a performance
+    disadvantage compared to plain old classes.
+    """
+    return str(annot).startswith(_classvar_prefixes)
+
+
+def _get_annotations(cls):
+    """
+    Get annotations for *cls*.
+    """
+    anns = getattr(cls, "__annotations__", None)
+    if anns is None:
+        return {}
+
+    # Verify that the annotations aren't merely inherited.
+    for base_cls in cls.__mro__[1:]:
+        if anns is getattr(base_cls, "__annotations__", None):
+            return {}
+
+    return anns
+
+
+def _counter_getter(e):
+    """
+    Key function for sorting to avoid re-creating a lambda for every class.
+    """
+    return e[1].counter
+
+
+def _transform_attrs(cls, these, auto_attribs, kw_only):
+    """
+    Transform all `_CountingAttr`s on a class into `Attribute`s.
+
+    If *these* is passed, use that and don't look for them on the class.
+
+    Return an `_Attributes`.
+    """
+    cd = cls.__dict__
+    anns = _get_annotations(cls)
+
+    if these is not None:
+        ca_list = [(name, ca) for name, ca in iteritems(these)]
+
+        if not isinstance(these, ordered_dict):
+            ca_list.sort(key=_counter_getter)
+    elif auto_attribs is True:
+        ca_names = {
+            name
+            for name, attr in cd.items()
+            if isinstance(attr, _CountingAttr)
+        }
+        ca_list = []
+        annot_names = set()
+        for attr_name, type in anns.items():
+            if _is_class_var(type):
+                continue
+            annot_names.add(attr_name)
+            a = cd.get(attr_name, NOTHING)
+            if not isinstance(a, _CountingAttr):
+                if a is NOTHING:
+                    a = attrib()
+                else:
+                    a = attrib(default=a)
+            ca_list.append((attr_name, a))
+
+        unannotated = ca_names - annot_names
+        if len(unannotated) > 0:
+            raise UnannotatedAttributeError(
+                "The following `attr.ib`s lack a type annotation: "
+                + ", ".join(
+                    sorted(unannotated, key=lambda n: cd.get(n).counter)
+                )
+                + "."
+            )
+    else:
+        ca_list = sorted(
+            (
+                (name, attr)
+                for name, attr in cd.items()
+                if isinstance(attr, _CountingAttr)
+            ),
+            key=lambda e: e[1].counter,
+        )
+
+    own_attrs = [
+        Attribute.from_counting_attr(
+            name=attr_name, ca=ca, type=anns.get(attr_name)
+        )
+        for attr_name, ca in ca_list
+    ]
+
+    base_attrs = []
+    base_attr_map = {}  # A dictionary of base attrs to their classes.
+    taken_attr_names = {a.name: a for a in own_attrs}
+
+    # Traverse the MRO and collect attributes.
+    for base_cls in cls.__mro__[1:-1]:
+        sub_attrs = getattr(base_cls, "__attrs_attrs__", None)
+        if sub_attrs is not None:
+            for a in sub_attrs:
+                prev_a = taken_attr_names.get(a.name)
+                # Only add an attribute if it hasn't been defined before.  This
+                # allows for overwriting attribute definitions by subclassing.
+                if prev_a is None:
+                    base_attrs.append(a)
+                    taken_attr_names[a.name] = a
+                    base_attr_map[a.name] = base_cls
+
+    attr_names = [a.name for a in base_attrs + own_attrs]
+
+    AttrsClass = _make_attr_tuple_class(cls.__name__, attr_names)
+
+    if kw_only:
+        own_attrs = [a._assoc(kw_only=True) for a in own_attrs]
+        base_attrs = [a._assoc(kw_only=True) for a in base_attrs]
+
+    attrs = AttrsClass(base_attrs + own_attrs)
+
+    # Mandatory vs non-mandatory attr order only matters when they are part of
+    # the __init__ signature and when they aren't kw_only (which are moved to
+    # the end and can be mandatory or non-mandatory in any order, as they will
+    # be specified as keyword args anyway). Check the order of those attrs:
+    had_default = False
+    for a in (a for a in attrs if a.init is not False and a.kw_only is False):
+        if had_default is True and a.default is NOTHING:
+            raise ValueError(
+                "No mandatory attributes allowed after an attribute with a "
+                "default value or factory.  Attribute in question: %r" % (a,)
+            )
+
+        if had_default is False and a.default is not NOTHING:
+            had_default = True
+
+    return _Attributes((attrs, base_attrs, base_attr_map))
+
+
+def _frozen_setattrs(self, name, value):
+    """
+    Attached to frozen classes as __setattr__.
+    """
+    raise FrozenInstanceError()
+
+
+def _frozen_delattrs(self, name):
+    """
+    Attached to frozen classes as __delattr__.
+    """
+    raise FrozenInstanceError()
+
+
+class _ClassBuilder(object):
+    """
+    Iteratively build *one* class.
+    """
+
+    __slots__ = (
+        "_cls",
+        "_cls_dict",
+        "_attrs",
+        "_base_names",
+        "_attr_names",
+        "_slots",
+        "_frozen",
+        "_weakref_slot",
+        "_cache_hash",
+        "_has_post_init",
+        "_delete_attribs",
+        "_base_attr_map",
+        "_is_exc",
+    )
+
+    def __init__(
+        self,
+        cls,
+        these,
+        slots,
+        frozen,
+        weakref_slot,
+        auto_attribs,
+        kw_only,
+        cache_hash,
+        is_exc,
+    ):
+        attrs, base_attrs, base_map = _transform_attrs(
+            cls, these, auto_attribs, kw_only
+        )
+
+        self._cls = cls
+        self._cls_dict = dict(cls.__dict__) if slots else {}
+        self._attrs = attrs
+        self._base_names = set(a.name for a in base_attrs)
+        self._base_attr_map = base_map
+        self._attr_names = tuple(a.name for a in attrs)
+        self._slots = slots
+        self._frozen = frozen or _has_frozen_base_class(cls)
+        self._weakref_slot = weakref_slot
+        self._cache_hash = cache_hash
+        self._has_post_init = bool(getattr(cls, "__attrs_post_init__", False))
+        self._delete_attribs = not bool(these)
+        self._is_exc = is_exc
+
+        self._cls_dict["__attrs_attrs__"] = self._attrs
+
+        if frozen:
+            self._cls_dict["__setattr__"] = _frozen_setattrs
+            self._cls_dict["__delattr__"] = _frozen_delattrs
+
+    def __repr__(self):
+        return "<_ClassBuilder(cls={cls})>".format(cls=self._cls.__name__)
+
+    def build_class(self):
+        """
+        Finalize class based on the accumulated configuration.
+
+        Builder cannot be used after calling this method.
+        """
+        if self._slots is True:
+            return self._create_slots_class()
+        else:
+            return self._patch_original_class()
+
+    def _patch_original_class(self):
+        """
+        Apply accumulated methods and return the class.
+        """
+        cls = self._cls
+        base_names = self._base_names
+
+        # Clean class of attribute definitions (`attr.ib()`s).
+        if self._delete_attribs:
+            for name in self._attr_names:
+                if (
+                    name not in base_names
+                    and getattr(cls, name, _sentinel) != _sentinel
+                ):
+                    try:
+                        delattr(cls, name)
+                    except AttributeError:
+                        # This can happen if a base class defines a class
+                        # variable and we want to set an attribute with the
+                        # same name by using only a type annotation.
+                        pass
+
+        # Attach our dunder methods.
+        for name, value in self._cls_dict.items():
+            setattr(cls, name, value)
+
+        # Attach __setstate__. This is necessary to clear the hash code
+        # cache on deserialization. See issue
+        # https://github.com/python-attrs/attrs/issues/482 .
+        # Note that this code only handles setstate for dict classes.
+        # For slotted classes, see similar code in _create_slots_class .
+        if self._cache_hash:
+            existing_set_state_method = getattr(cls, "__setstate__", None)
+            if existing_set_state_method:
+                raise NotImplementedError(
+                    "Currently you cannot use hash caching if "
+                    "you specify your own __setstate__ method."
+                    "See https://github.com/python-attrs/attrs/issues/494 ."
+                )
+
+            def cache_hash_set_state(chss_self, _):
+                # clear hash code cache
+                setattr(chss_self, _hash_cache_field, None)
+
+            setattr(cls, "__setstate__", cache_hash_set_state)
+
+        return cls
+
+    def _create_slots_class(self):
+        """
+        Build and return a new class with a `__slots__` attribute.
+        """
+        base_names = self._base_names
+        cd = {
+            k: v
+            for k, v in iteritems(self._cls_dict)
+            if k not in tuple(self._attr_names) + ("__dict__", "__weakref__")
+        }
+
+        weakref_inherited = False
+
+        # Traverse the MRO to check for an existing __weakref__.
+        for base_cls in self._cls.__mro__[1:-1]:
+            if "__weakref__" in getattr(base_cls, "__dict__", ()):
+                weakref_inherited = True
+                break
+
+        names = self._attr_names
+        if (
+            self._weakref_slot
+            and "__weakref__" not in getattr(self._cls, "__slots__", ())
+            and "__weakref__" not in names
+            and not weakref_inherited
+        ):
+            names += ("__weakref__",)
+
+        # We only add the names of attributes that aren't inherited.
+        # Settings __slots__ to inherited attributes wastes memory.
+        slot_names = [name for name in names if name not in base_names]
+        if self._cache_hash:
+            slot_names.append(_hash_cache_field)
+        cd["__slots__"] = tuple(slot_names)
+
+        qualname = getattr(self._cls, "__qualname__", None)
+        if qualname is not None:
+            cd["__qualname__"] = qualname
+
+        # __weakref__ is not writable.
+        state_attr_names = tuple(
+            an for an in self._attr_names if an != "__weakref__"
+        )
+
+        def slots_getstate(self):
+            """
+            Automatically created by attrs.
+            """
+            return tuple(getattr(self, name) for name in state_attr_names)
+
+        hash_caching_enabled = self._cache_hash
+
+        def slots_setstate(self, state):
+            """
+            Automatically created by attrs.
+            """
+            __bound_setattr = _obj_setattr.__get__(self, Attribute)
+            for name, value in zip(state_attr_names, state):
+                __bound_setattr(name, value)
+            # Clearing the hash code cache on deserialization is needed
+            # because hash codes can change from run to run. See issue
+            # https://github.com/python-attrs/attrs/issues/482 .
+            # Note that this code only handles setstate for slotted classes.
+            # For dict classes, see similar code in _patch_original_class .
+            if hash_caching_enabled:
+                __bound_setattr(_hash_cache_field, None)
+
+        # slots and frozen require __getstate__/__setstate__ to work
+        cd["__getstate__"] = slots_getstate
+        cd["__setstate__"] = slots_setstate
+
+        # Create new class based on old class and our methods.
+        cls = type(self._cls)(self._cls.__name__, self._cls.__bases__, cd)
+
+        # The following is a fix for
+        # https://github.com/python-attrs/attrs/issues/102.  On Python 3,
+        # if a method mentions `__class__` or uses the no-arg super(), the
+        # compiler will bake a reference to the class in the method itself
+        # as `method.__closure__`.  Since we replace the class with a
+        # clone, we rewrite these references so it keeps working.
+        for item in cls.__dict__.values():
+            if isinstance(item, (classmethod, staticmethod)):
+                # Class- and staticmethods hide their functions inside.
+                # These might need to be rewritten as well.
+                closure_cells = getattr(item.__func__, "__closure__", None)
+            else:
+                closure_cells = getattr(item, "__closure__", None)
+
+            if not closure_cells:  # Catch None or the empty list.
+                continue
+            for cell in closure_cells:
+                if cell.cell_contents is self._cls:
+                    set_closure_cell(cell, cls)
+
+        return cls
+
+    def add_repr(self, ns):
+        self._cls_dict["__repr__"] = self._add_method_dunders(
+            _make_repr(self._attrs, ns=ns)
+        )
+        return self
+
+    def add_str(self):
+        repr = self._cls_dict.get("__repr__")
+        if repr is None:
+            raise ValueError(
+                "__str__ can only be generated if a __repr__ exists."
+            )
+
+        def __str__(self):
+            return self.__repr__()
+
+        self._cls_dict["__str__"] = self._add_method_dunders(__str__)
+        return self
+
+    def make_unhashable(self):
+        self._cls_dict["__hash__"] = None
+        return self
+
+    def add_hash(self):
+        self._cls_dict["__hash__"] = self._add_method_dunders(
+            _make_hash(
+                self._cls,
+                self._attrs,
+                frozen=self._frozen,
+                cache_hash=self._cache_hash,
+            )
+        )
+
+        return self
+
+    def add_init(self):
+        self._cls_dict["__init__"] = self._add_method_dunders(
+            _make_init(
+                self._cls,
+                self._attrs,
+                self._has_post_init,
+                self._frozen,
+                self._slots,
+                self._cache_hash,
+                self._base_attr_map,
+                self._is_exc,
+            )
+        )
+
+        return self
+
+    def add_eq(self):
+        cd = self._cls_dict
+
+        cd["__eq__"], cd["__ne__"] = (
+            self._add_method_dunders(meth)
+            for meth in _make_eq(self._cls, self._attrs)
+        )
+
+        return self
+
+    def add_order(self):
+        cd = self._cls_dict
+
+        cd["__lt__"], cd["__le__"], cd["__gt__"], cd["__ge__"] = (
+            self._add_method_dunders(meth)
+            for meth in _make_order(self._cls, self._attrs)
+        )
+
+        return self
+
+    def _add_method_dunders(self, method):
+        """
+        Add __module__ and __qualname__ to a *method* if possible.
+        """
+        try:
+            method.__module__ = self._cls.__module__
+        except AttributeError:
+            pass
+
+        try:
+            method.__qualname__ = ".".join(
+                (self._cls.__qualname__, method.__name__)
+            )
+        except AttributeError:
+            pass
+
+        return method
+
+
+_CMP_DEPRECATION = (
+    "The usage of `cmp` is deprecated and will be removed on or after "
+    "2021-06-01.  Please use `eq` and `order` instead."
+)
+
+
+def _determine_eq_order(cmp, eq, order):
+    """
+    Validate the combination of *cmp*, *eq*, and *order*. Derive the effective
+    values of eq and order.
+    """
+    if cmp is not None and any((eq is not None, order is not None)):
+        raise ValueError("Don't mix `cmp` with `eq' and `order`.")
+
+    # cmp takes precedence due to bw-compatibility.
+    if cmp is not None:
+        warnings.warn(_CMP_DEPRECATION, DeprecationWarning, stacklevel=3)
+
+        return cmp, cmp
+
+    # If left None, equality is on and ordering mirrors equality.
+    if eq is None:
+        eq = True
+
+    if order is None:
+        order = eq
+
+    if eq is False and order is True:
+        raise ValueError("`order` can only be True if `eq` is True too.")
+
+    return eq, order
+
+
+def attrs(
+    maybe_cls=None,
+    these=None,
+    repr_ns=None,
+    repr=True,
+    cmp=None,
+    hash=None,
+    init=True,
+    slots=False,
+    frozen=False,
+    weakref_slot=True,
+    str=False,
+    auto_attribs=False,
+    kw_only=False,
+    cache_hash=False,
+    auto_exc=False,
+    eq=None,
+    order=None,
+):
+    r"""
+    A class decorator that adds `dunder
+    <https://wiki.python.org/moin/DunderAlias>`_\ -methods according to the
+    specified attributes using `attr.ib` or the *these* argument.
+
+    :param these: A dictionary of name to `attr.ib` mappings.  This is
+        useful to avoid the definition of your attributes within the class body
+        because you can't (e.g. if you want to add ``__repr__`` methods to
+        Django models) or don't want to.
+
+        If *these* is not ``None``, ``attrs`` will *not* search the class body
+        for attributes and will *not* remove any attributes from it.
+
+        If *these* is an ordered dict (`dict` on Python 3.6+,
+        `collections.OrderedDict` otherwise), the order is deduced from
+        the order of the attributes inside *these*.  Otherwise the order
+        of the definition of the attributes is used.
+
+    :type these: `dict` of `str` to `attr.ib`
+
+    :param str repr_ns: When using nested classes, there's no way in Python 2
+        to automatically detect that.  Therefore it's possible to set the
+        namespace explicitly for a more meaningful ``repr`` output.
+    :param bool repr: Create a ``__repr__`` method with a human readable
+        representation of ``attrs`` attributes..
+    :param bool str: Create a ``__str__`` method that is identical to
+        ``__repr__``.  This is usually not necessary except for
+        `Exception`\ s.
+    :param bool eq: If ``True`` or ``None`` (default), add ``__eq__`` and
+        ``__ne__`` methods that check two instances for equality.
+
+        They compare the instances as if they were tuples of their ``attrs``
+        attributes, but only iff the types of both classes are *identical*!
+    :type eq: `bool` or `None`
+    :param bool order: If ``True``, add ``__lt__``, ``__le__``, ``__gt__``,
+        and ``__ge__`` methods that behave like *eq* above and allow instances
+        to be ordered. If ``None`` (default) mirror value of *eq*.
+    :type order: `bool` or `None`
+    :param cmp: Setting to ``True`` is equivalent to setting ``eq=True,
+        order=True``. Deprecated in favor of *eq* and *order*, has precedence
+        over them for backward-compatibility though. Must not be mixed with
+        *eq* or *order*.
+    :type cmp: `bool` or `None`
+    :param hash: If ``None`` (default), the ``__hash__`` method is generated
+        according how *eq* and *frozen* are set.
+
+        1. If *both* are True, ``attrs`` will generate a ``__hash__`` for you.
+        2. If *eq* is True and *frozen* is False, ``__hash__`` will be set to
+           None, marking it unhashable (which it is).
+        3. If *eq* is False, ``__hash__`` will be left untouched meaning the
+           ``__hash__`` method of the base class will be used (if base class is
+           ``object``, this means it will fall back to id-based hashing.).
+
+        Although not recommended, you can decide for yourself and force
+        ``attrs`` to create one (e.g. if the class is immutable even though you
+        didn't freeze it programmatically) by passing ``True`` or not.  Both of
+        these cases are rather special and should be used carefully.
+
+        See our documentation on `hashing`, Python's documentation on
+        `object.__hash__`, and the `GitHub issue that led to the default \
+        behavior <https://github.com/python-attrs/attrs/issues/136>`_ for more
+        details.
+    :type hash: ``bool`` or ``None``
+    :param bool init: Create a ``__init__`` method that initializes the
+        ``attrs`` attributes.  Leading underscores are stripped for the
+        argument name.  If a ``__attrs_post_init__`` method exists on the
+        class, it will be called after the class is fully initialized.
+    :param bool slots: Create a `slotted class <slotted classes>` that's more
+        memory-efficient.
+    :param bool frozen: Make instances immutable after initialization.  If
+        someone attempts to modify a frozen instance,
+        `attr.exceptions.FrozenInstanceError` is raised.
+
+        Please note:
+
+            1. This is achieved by installing a custom ``__setattr__`` method
+               on your class so you can't implement an own one.
+
+            2. True immutability is impossible in Python.
+
+            3. This *does* have a minor a runtime performance `impact
+               <how-frozen>` when initializing new instances.  In other words:
+               ``__init__`` is slightly slower with ``frozen=True``.
+
+            4. If a class is frozen, you cannot modify ``self`` in
+               ``__attrs_post_init__`` or a self-written ``__init__``. You can
+               circumvent that limitation by using
+               ``object.__setattr__(self, "attribute_name", value)``.
+
+    :param bool weakref_slot: Make instances weak-referenceable.  This has no
+        effect unless ``slots`` is also enabled.
+    :param bool auto_attribs: If True, collect `PEP 526`_-annotated attributes
+        (Python 3.6 and later only) from the class body.
+
+        In this case, you **must** annotate every field.  If ``attrs``
+        encounters a field that is set to an `attr.ib` but lacks a type
+        annotation, an `attr.exceptions.UnannotatedAttributeError` is
+        raised.  Use ``field_name: typing.Any = attr.ib(...)`` if you don't
+        want to set a type.
+
+        If you assign a value to those attributes (e.g. ``x: int = 42``), that
+        value becomes the default value like if it were passed using
+        ``attr.ib(default=42)``.  Passing an instance of `Factory` also
+        works as expected.
+
+        Attributes annotated as `typing.ClassVar`, and attributes that are
+        neither annotated nor set to an `attr.ib` are **ignored**.
+
+        .. _`PEP 526`: https://www.python.org/dev/peps/pep-0526/
+    :param bool kw_only: Make all attributes keyword-only (Python 3+)
+        in the generated ``__init__`` (if ``init`` is ``False``, this
+        parameter is ignored).
+    :param bool cache_hash: Ensure that the object's hash code is computed
+        only once and stored on the object.  If this is set to ``True``,
+        hashing must be either explicitly or implicitly enabled for this
+        class.  If the hash code is cached, avoid any reassignments of
+        fields involved in hash code computation or mutations of the objects
+        those fields point to after object creation.  If such changes occur,
+        the behavior of the object's hash code is undefined.
+    :param bool auto_exc: If the class subclasses `BaseException`
+        (which implicitly includes any subclass of any exception), the
+        following happens to behave like a well-behaved Python exceptions
+        class:
+
+        - the values for *eq*, *order*, and *hash* are ignored and the
+          instances compare and hash by the instance's ids (N.B. ``attrs`` will
+          *not* remove existing implementations of ``__hash__`` or the equality
+          methods. It just won't add own ones.),
+        - all attributes that are either passed into ``__init__`` or have a
+          default value are additionally available as a tuple in the ``args``
+          attribute,
+        - the value of *str* is ignored leaving ``__str__`` to base classes.
+
+    .. versionadded:: 16.0.0 *slots*
+    .. versionadded:: 16.1.0 *frozen*
+    .. versionadded:: 16.3.0 *str*
+    .. versionadded:: 16.3.0 Support for ``__attrs_post_init__``.
+    .. versionchanged:: 17.1.0
+       *hash* supports ``None`` as value which is also the default now.
+    .. versionadded:: 17.3.0 *auto_attribs*
+    .. versionchanged:: 18.1.0
+       If *these* is passed, no attributes are deleted from the class body.
+    .. versionchanged:: 18.1.0 If *these* is ordered, the order is retained.
+    .. versionadded:: 18.2.0 *weakref_slot*
+    .. deprecated:: 18.2.0
+       ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now raise a
+       `DeprecationWarning` if the classes compared are subclasses of
+       each other. ``__eq`` and ``__ne__`` never tried to compared subclasses
+       to each other.
+    .. versionchanged:: 19.2.0
+       ``__lt__``, ``__le__``, ``__gt__``, and ``__ge__`` now do not consider
+       subclasses comparable anymore.
+    .. versionadded:: 18.2.0 *kw_only*
+    .. versionadded:: 18.2.0 *cache_hash*
+    .. versionadded:: 19.1.0 *auto_exc*
+    .. deprecated:: 19.2.0 *cmp* Removal on or after 2021-06-01.
+    .. versionadded:: 19.2.0 *eq* and *order*
+    """
+    eq, order = _determine_eq_order(cmp, eq, order)
+
+    def wrap(cls):
+
+        if getattr(cls, "__class__", None) is None:
+            raise TypeError("attrs only works with new-style classes.")
+
+        is_exc = auto_exc is True and issubclass(cls, BaseException)
+
+        builder = _ClassBuilder(
+            cls,
+            these,
+            slots,
+            frozen,
+            weakref_slot,
+            auto_attribs,
+            kw_only,
+            cache_hash,
+            is_exc,
+        )
+
+        if repr is True:
+            builder.add_repr(repr_ns)
+        if str is True:
+            builder.add_str()
+        if eq is True and not is_exc:
+            builder.add_eq()
+        if order is True and not is_exc:
+            builder.add_order()
+
+        if hash is not True and hash is not False and hash is not None:
+            # Can't use `hash in` because 1 == True for example.
+            raise TypeError(
+                "Invalid value for hash.  Must be True, False, or None."
+            )
+        elif hash is False or (hash is None and eq is False) or is_exc:
+            # Don't do anything. Should fall back to __object__'s __hash__
+            # which is by id.
+            if cache_hash:
+                raise TypeError(
+                    "Invalid value for cache_hash.  To use hash caching,"
+                    " hashing must be either explicitly or implicitly "
+                    "enabled."
+                )
+        elif hash is True or (hash is None and eq is True and frozen is True):
+            # Build a __hash__ if told so, or if it's safe.
+            builder.add_hash()
+        else:
+            # Raise TypeError on attempts to hash.
+            if cache_hash:
+                raise TypeError(
+                    "Invalid value for cache_hash.  To use hash caching,"
+                    " hashing must be either explicitly or implicitly "
+                    "enabled."
+                )
+            builder.make_unhashable()
+
+        if init is True:
+            builder.add_init()
+        else:
+            if cache_hash:
+                raise TypeError(
+                    "Invalid value for cache_hash.  To use hash caching,"
+                    " init must be True."
+                )
+
+        return builder.build_class()
+
+    # maybe_cls's type depends on the usage of the decorator.  It's a class
+    # if it's used as `@attrs` but ``None`` if used as `@attrs()`.
+    if maybe_cls is None:
+        return wrap
+    else:
+        return wrap(maybe_cls)
+
+
+_attrs = attrs
+"""
+Internal alias so we can use it in functions that take an argument called
+*attrs*.
+"""
+
+
+if PY2:
+
+    def _has_frozen_base_class(cls):
+        """
+        Check whether *cls* has a frozen ancestor by looking at its
+        __setattr__.
+        """
+        return (
+            getattr(cls.__setattr__, "__module__", None)
+            == _frozen_setattrs.__module__
+            and cls.__setattr__.__name__ == _frozen_setattrs.__name__
+        )
+
+
+else:
+
+    def _has_frozen_base_class(cls):
+        """
+        Check whether *cls* has a frozen ancestor by looking at its
+        __setattr__.
+        """
+        return cls.__setattr__ == _frozen_setattrs
+
+
+def _attrs_to_tuple(obj, attrs):
+    """
+    Create a tuple of all values of *obj*'s *attrs*.
+    """
+    return tuple(getattr(obj, a.name) for a in attrs)
+
+
+def _generate_unique_filename(cls, func_name):
+    """
+    Create a "filename" suitable for a function being generated.
+    """
+    unique_id = uuid.uuid4()
+    extra = ""
+    count = 1
+
+    while True:
+        unique_filename = "<attrs generated {0} {1}.{2}{3}>".format(
+            func_name,
+            cls.__module__,
+            getattr(cls, "__qualname__", cls.__name__),
+            extra,
+        )
+        # To handle concurrency we essentially "reserve" our spot in
+        # the linecache with a dummy line.  The caller can then
+        # set this value correctly.
+        cache_line = (1, None, (str(unique_id),), unique_filename)
+        if (
+            linecache.cache.setdefault(unique_filename, cache_line)
+            == cache_line
+        ):
+            return unique_filename
+
+        # Looks like this spot is taken. Try again.
+        count += 1
+        extra = "-{0}".format(count)
+
+
+def _make_hash(cls, attrs, frozen, cache_hash):
+    attrs = tuple(
+        a for a in attrs if a.hash is True or (a.hash is None and a.eq is True)
+    )
+
+    tab = "        "
+
+    unique_filename = _generate_unique_filename(cls, "hash")
+    type_hash = hash(unique_filename)
+
+    method_lines = ["def __hash__(self):"]
+
+    def append_hash_computation_lines(prefix, indent):
+        """
+        Generate the code for actually computing the hash code.
+        Below this will either be returned directly or used to compute
+        a value which is then cached, depending on the value of cache_hash
+        """
+        method_lines.extend(
+            [indent + prefix + "hash((", indent + "        %d," % (type_hash,)]
+        )
+
+        for a in attrs:
+            method_lines.append(indent + "        self.%s," % a.name)
+
+        method_lines.append(indent + "    ))")
+
+    if cache_hash:
+        method_lines.append(tab + "if self.%s is None:" % _hash_cache_field)
+        if frozen:
+            append_hash_computation_lines(
+                "object.__setattr__(self, '%s', " % _hash_cache_field, tab * 2
+            )
+            method_lines.append(tab * 2 + ")")  # close __setattr__
+        else:
+            append_hash_computation_lines(
+                "self.%s = " % _hash_cache_field, tab * 2
+            )
+        method_lines.append(tab + "return self.%s" % _hash_cache_field)
+    else:
+        append_hash_computation_lines("return ", tab)
+
+    script = "\n".join(method_lines)
+    globs = {}
+    locs = {}
+    bytecode = compile(script, unique_filename, "exec")
+    eval(bytecode, globs, locs)
+
+    # In order of debuggers like PDB being able to step through the code,
+    # we add a fake linecache entry.
+    linecache.cache[unique_filename] = (
+        len(script),
+        None,
+        script.splitlines(True),
+        unique_filename,
+    )
+
+    return locs["__hash__"]
+
+
+def _add_hash(cls, attrs):
+    """
+    Add a hash method to *cls*.
+    """
+    cls.__hash__ = _make_hash(cls, attrs, frozen=False, cache_hash=False)
+    return cls
+
+
+def __ne__(self, other):
+    """
+    Check equality and either forward a NotImplemented or return the result
+    negated.
+    """
+    result = self.__eq__(other)
+    if result is NotImplemented:
+        return NotImplemented
+
+    return not result
+
+
+def _make_eq(cls, attrs):
+    attrs = [a for a in attrs if a.eq]
+
+    unique_filename = _generate_unique_filename(cls, "eq")
+    lines = [
+        "def __eq__(self, other):",
+        "    if other.__class__ is not self.__class__:",
+        "        return NotImplemented",
+    ]
+    # We can't just do a big self.x = other.x and... clause due to
+    # irregularities like nan == nan is false but (nan,) == (nan,) is true.
+    if attrs:
+        lines.append("    return  (")
+        others = ["    ) == ("]
+        for a in attrs:
+            lines.append("        self.%s," % (a.name,))
+            others.append("        other.%s," % (a.name,))
+
+        lines += others + ["    )"]
+    else:
+        lines.append("    return True")
+
+    script = "\n".join(lines)
+    globs = {}
+    locs = {}
+    bytecode = compile(script, unique_filename, "exec")
+    eval(bytecode, globs, locs)
+
+    # In order of debuggers like PDB being able to step through the code,
+    # we add a fake linecache entry.
+    linecache.cache[unique_filename] = (
+        len(script),
+        None,
+        script.splitlines(True),
+        unique_filename,
+    )
+    return locs["__eq__"], __ne__
+
+
+def _make_order(cls, attrs):
+    attrs = [a for a in attrs if a.order]
+
+    def attrs_to_tuple(obj):
+        """
+        Save us some typing.
+        """
+        return _attrs_to_tuple(obj, attrs)
+
+    def __lt__(self, other):
+        """
+        Automatically created by attrs.
+        """
+        if other.__class__ is self.__class__:
+            return attrs_to_tuple(self) < attrs_to_tuple(other)
+
+        return NotImplemented
+
+    def __le__(self, other):
+        """
+        Automatically created by attrs.
+        """
+        if other.__class__ is self.__class__:
+            return attrs_to_tuple(self) <= attrs_to_tuple(other)
+
+        return NotImplemented
+
+    def __gt__(self, other):
+        """
+        Automatically created by attrs.
+        """
+        if other.__class__ is self.__class__:
+            return attrs_to_tuple(self) > attrs_to_tuple(other)
+
+        return NotImplemented
+
+    def __ge__(self, other):
+        """
+        Automatically created by attrs.
+        """
+        if other.__class__ is self.__class__:
+            return attrs_to_tuple(self) >= attrs_to_tuple(other)
+
+        return NotImplemented
+
+    return __lt__, __le__, __gt__, __ge__
+
+
+def _add_eq(cls, attrs=None):
+    """
+    Add equality methods to *cls* with *attrs*.
+    """
+    if attrs is None:
+        attrs = cls.__attrs_attrs__
+
+    cls.__eq__, cls.__ne__ = _make_eq(cls, attrs)
+
+    return cls
+
+
+_already_repring = threading.local()
+
+
+def _make_repr(attrs, ns):
+    """
+    Make a repr method that includes relevant *attrs*, adding *ns* to the full
+    name.
+    """
+
+    # Figure out which attributes to include, and which function to use to
+    # format them. The a.repr value can be either bool or a custom callable.
+    attr_names_with_reprs = tuple(
+        (a.name, repr if a.repr is True else a.repr)
+        for a in attrs
+        if a.repr is not False
+    )
+
+    def __repr__(self):
+        """
+        Automatically created by attrs.
+        """
+        try:
+            working_set = _already_repring.working_set
+        except AttributeError:
+            working_set = set()
+            _already_repring.working_set = working_set
+
+        if id(self) in working_set:
+            return "..."
+        real_cls = self.__class__
+        if ns is None:
+            qualname = getattr(real_cls, "__qualname__", None)
+            if qualname is not None:
+                class_name = qualname.rsplit(">.", 1)[-1]
+            else:
+                class_name = real_cls.__name__
+        else:
+            class_name = ns + "." + real_cls.__name__
+
+        # Since 'self' remains on the stack (i.e.: strongly referenced) for the
+        # duration of this call, it's safe to depend on id(...) stability, and
+        # not need to track the instance and therefore worry about properties
+        # like weakref- or hash-ability.
+        working_set.add(id(self))
+        try:
+            result = [class_name, "("]
+            first = True
+            for name, attr_repr in attr_names_with_reprs:
+                if first:
+                    first = False
+                else:
+                    result.append(", ")
+                result.extend(
+                    (name, "=", attr_repr(getattr(self, name, NOTHING)))
+                )
+            return "".join(result) + ")"
+        finally:
+            working_set.remove(id(self))
+
+    return __repr__
+
+
+def _add_repr(cls, ns=None, attrs=None):
+    """
+    Add a repr method to *cls*.
+    """
+    if attrs is None:
+        attrs = cls.__attrs_attrs__
+
+    cls.__repr__ = _make_repr(attrs, ns)
+    return cls
+
+
+def _make_init(
+    cls, attrs, post_init, frozen, slots, cache_hash, base_attr_map, is_exc
+):
+    attrs = [a for a in attrs if a.init or a.default is not NOTHING]
+
+    unique_filename = _generate_unique_filename(cls, "init")
+
+    script, globs, annotations = _attrs_to_init_script(
+        attrs, frozen, slots, post_init, cache_hash, base_attr_map, is_exc
+    )
+    locs = {}
+    bytecode = compile(script, unique_filename, "exec")
+    attr_dict = dict((a.name, a) for a in attrs)
+    globs.update({"NOTHING": NOTHING, "attr_dict": attr_dict})
+
+    if frozen is True:
+        # Save the lookup overhead in __init__ if we need to circumvent
+        # immutability.
+        globs["_cached_setattr"] = _obj_setattr
+
+    eval(bytecode, globs, locs)
+
+    # In order of debuggers like PDB being able to step through the code,
+    # we add a fake linecache entry.
+    linecache.cache[unique_filename] = (
+        len(script),
+        None,
+        script.splitlines(True),
+        unique_filename,
+    )
+
+    __init__ = locs["__init__"]
+    __init__.__annotations__ = annotations
+
+    return __init__
+
+
+def fields(cls):
+    """
+    Return the tuple of ``attrs`` attributes for a class.
+
+    The tuple also allows accessing the fields by their names (see below for
+    examples).
+
+    :param type cls: Class to introspect.
+
+    :raise TypeError: If *cls* is not a class.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    :rtype: tuple (with name accessors) of `attr.Attribute`
+
+    ..  versionchanged:: 16.2.0 Returned tuple allows accessing the fields
+        by name.
+    """
+    if not isclass(cls):
+        raise TypeError("Passed object must be a class.")
+    attrs = getattr(cls, "__attrs_attrs__", None)
+    if attrs is None:
+        raise NotAnAttrsClassError(
+            "{cls!r} is not an attrs-decorated class.".format(cls=cls)
+        )
+    return attrs
+
+
+def fields_dict(cls):
+    """
+    Return an ordered dictionary of ``attrs`` attributes for a class, whose
+    keys are the attribute names.
+
+    :param type cls: Class to introspect.
+
+    :raise TypeError: If *cls* is not a class.
+    :raise attr.exceptions.NotAnAttrsClassError: If *cls* is not an ``attrs``
+        class.
+
+    :rtype: an ordered dict where keys are attribute names and values are
+        `attr.Attribute`\\ s. This will be a `dict` if it's
+        naturally ordered like on Python 3.6+ or an
+        :class:`~collections.OrderedDict` otherwise.
+
+    .. versionadded:: 18.1.0
+    """
+    if not isclass(cls):
+        raise TypeError("Passed object must be a class.")
+    attrs = getattr(cls, "__attrs_attrs__", None)
+    if attrs is None:
+        raise NotAnAttrsClassError(
+            "{cls!r} is not an attrs-decorated class.".format(cls=cls)
+        )
+    return ordered_dict(((a.name, a) for a in attrs))
+
+
+def validate(inst):
+    """
+    Validate all attributes on *inst* that have a validator.
+
+    Leaves all exceptions through.
+
+    :param inst: Instance of a class with ``attrs`` attributes.
+    """
+    if _config._run_validators is False:
+        return
+
+    for a in fields(inst.__class__):
+        v = a.validator
+        if v is not None:
+            v(inst, a, getattr(inst, a.name))
+
+
+def _is_slot_cls(cls):
+    return "__slots__" in cls.__dict__
+
+
+def _is_slot_attr(a_name, base_attr_map):
+    """
+    Check if the attribute name comes from a slot class.
+    """
+    return a_name in base_attr_map and _is_slot_cls(base_attr_map[a_name])
+
+
+def _attrs_to_init_script(
+    attrs, frozen, slots, post_init, cache_hash, base_attr_map, is_exc
+):
+    """
+    Return a script of an initializer for *attrs* and a dict of globals.
+
+    The globals are expected by the generated script.
+
+    If *frozen* is True, we cannot set the attributes directly so we use
+    a cached ``object.__setattr__``.
+    """
+    lines = []
+    any_slot_ancestors = any(
+        _is_slot_attr(a.name, base_attr_map) for a in attrs
+    )
+    if frozen is True:
+        if slots is True:
+            lines.append(
+                # Circumvent the __setattr__ descriptor to save one lookup per
+                # assignment.
+                # Note _setattr will be used again below if cache_hash is True
+                "_setattr = _cached_setattr.__get__(self, self.__class__)"
+            )
+
+            def fmt_setter(attr_name, value_var):
+                return "_setattr('%(attr_name)s', %(value_var)s)" % {
+                    "attr_name": attr_name,
+                    "value_var": value_var,
+                }
+
+            def fmt_setter_with_converter(attr_name, value_var):
+                conv_name = _init_converter_pat.format(attr_name)
+                return "_setattr('%(attr_name)s', %(conv)s(%(value_var)s))" % {
+                    "attr_name": attr_name,
+                    "value_var": value_var,
+                    "conv": conv_name,
+                }
+
+        else:
+            # Dict frozen classes assign directly to __dict__.
+            # But only if the attribute doesn't come from an ancestor slot
+            # class.
+            # Note _inst_dict will be used again below if cache_hash is True
+            lines.append("_inst_dict = self.__dict__")
+            if any_slot_ancestors:
+                lines.append(
+                    # Circumvent the __setattr__ descriptor to save one lookup
+                    # per assignment.
+                    "_setattr = _cached_setattr.__get__(self, self.__class__)"
+                )
+
+            def fmt_setter(attr_name, value_var):
+                if _is_slot_attr(attr_name, base_attr_map):
+                    res = "_setattr('%(attr_name)s', %(value_var)s)" % {
+                        "attr_name": attr_name,
+                        "value_var": value_var,
+                    }
+                else:
+                    res = "_inst_dict['%(attr_name)s'] = %(value_var)s" % {
+                        "attr_name": attr_name,
+                        "value_var": value_var,
+                    }
+                return res
+
+            def fmt_setter_with_converter(attr_name, value_var):
+                conv_name = _init_converter_pat.format(attr_name)
+                if _is_slot_attr(attr_name, base_attr_map):
+                    tmpl = "_setattr('%(attr_name)s', %(c)s(%(value_var)s))"
+                else:
+                    tmpl = "_inst_dict['%(attr_name)s'] = %(c)s(%(value_var)s)"
+                return tmpl % {
+                    "attr_name": attr_name,
+                    "value_var": value_var,
+                    "c": conv_name,
+                }
+
+    else:
+        # Not frozen.
+        def fmt_setter(attr_name, value):
+            return "self.%(attr_name)s = %(value)s" % {
+                "attr_name": attr_name,
+                "value": value,
+            }
+
+        def fmt_setter_with_converter(attr_name, value_var):
+            conv_name = _init_converter_pat.format(attr_name)
+            return "self.%(attr_name)s = %(conv)s(%(value_var)s)" % {
+                "attr_name": attr_name,
+                "value_var": value_var,
+                "conv": conv_name,
+            }
+
+    args = []
+    kw_only_args = []
+    attrs_to_validate = []
+
+    # This is a dictionary of names to validator and converter callables.
+    # Injecting this into __init__ globals lets us avoid lookups.
+    names_for_globals = {}
+    annotations = {"return": None}
+
+    for a in attrs:
+        if a.validator:
+            attrs_to_validate.append(a)
+        attr_name = a.name
+        arg_name = a.name.lstrip("_")
+        has_factory = isinstance(a.default, Factory)
+        if has_factory and a.default.takes_self:
+            maybe_self = "self"
+        else:
+            maybe_self = ""
+        if a.init is False:
+            if has_factory:
+                init_factory_name = _init_factory_pat.format(a.name)
+                if a.converter is not None:
+                    lines.append(
+                        fmt_setter_with_converter(
+                            attr_name,
+                            init_factory_name + "({0})".format(maybe_self),
+                        )
+                    )
+                    conv_name = _init_converter_pat.format(a.name)
+                    names_for_globals[conv_name] = a.converter
+                else:
+                    lines.append(
+                        fmt_setter(
+                            attr_name,
+                            init_factory_name + "({0})".format(maybe_self),
+                        )
+                    )
+                names_for_globals[init_factory_name] = a.default.factory
+            else:
+                if a.converter is not None:
+                    lines.append(
+                        fmt_setter_with_converter(
+                            attr_name,
+                            "attr_dict['{attr_name}'].default".format(
+                                attr_name=attr_name
+                            ),
+                        )
+                    )
+                    conv_name = _init_converter_pat.format(a.name)
+                    names_for_globals[conv_name] = a.converter
+                else:
+                    lines.append(
+                        fmt_setter(
+                            attr_name,
+                            "attr_dict['{attr_name}'].default".format(
+                                attr_name=attr_name
+                            ),
+                        )
+                    )
+        elif a.default is not NOTHING and not has_factory:
+            arg = "{arg_name}=attr_dict['{attr_name}'].default".format(
+                arg_name=arg_name, attr_name=attr_name
+            )
+            if a.kw_only:
+                kw_only_args.append(arg)
+            else:
+                args.append(arg)
+            if a.converter is not None:
+                lines.append(fmt_setter_with_converter(attr_name, arg_name))
+                names_for_globals[
+                    _init_converter_pat.format(a.name)
+                ] = a.converter
+            else:
+                lines.append(fmt_setter(attr_name, arg_name))
+        elif has_factory:
+            arg = "{arg_name}=NOTHING".format(arg_name=arg_name)
+            if a.kw_only:
+                kw_only_args.append(arg)
+            else:
+                args.append(arg)
+            lines.append(
+                "if {arg_name} is not NOTHING:".format(arg_name=arg_name)
+            )
+            init_factory_name = _init_factory_pat.format(a.name)
+            if a.converter is not None:
+                lines.append(
+                    "    " + fmt_setter_with_converter(attr_name, arg_name)
+                )
+                lines.append("else:")
+                lines.append(
+                    "    "
+                    + fmt_setter_with_converter(
+                        attr_name,
+                        init_factory_name + "({0})".format(maybe_self),
+                    )
+                )
+                names_for_globals[
+                    _init_converter_pat.format(a.name)
+                ] = a.converter
+            else:
+                lines.append("    " + fmt_setter(attr_name, arg_name))
+                lines.append("else:")
+                lines.append(
+                    "    "
+                    + fmt_setter(
+                        attr_name,
+                        init_factory_name + "({0})".format(maybe_self),
+                    )
+                )
+            names_for_globals[init_factory_name] = a.default.factory
+        else:
+            if a.kw_only:
+                kw_only_args.append(arg_name)
+            else:
+                args.append(arg_name)
+            if a.converter is not None:
+                lines.append(fmt_setter_with_converter(attr_name, arg_name))
+                names_for_globals[
+                    _init_converter_pat.format(a.name)
+                ] = a.converter
+            else:
+                lines.append(fmt_setter(attr_name, arg_name))
+
+        if a.init is True and a.converter is None and a.type is not None:
+            annotations[arg_name] = a.type
+
+    if attrs_to_validate:  # we can skip this if there are no validators.
+        names_for_globals["_config"] = _config
+        lines.append("if _config._run_validators is True:")
+        for a in attrs_to_validate:
+            val_name = "__attr_validator_{}".format(a.name)
+            attr_name = "__attr_{}".format(a.name)
+            lines.append(
+                "    {}(self, {}, self.{})".format(val_name, attr_name, a.name)
+            )
+            names_for_globals[val_name] = a.validator
+            names_for_globals[attr_name] = a
+    if post_init:
+        lines.append("self.__attrs_post_init__()")
+
+    # because this is set only after __attrs_post_init is called, a crash
+    # will result if post-init tries to access the hash code.  This seemed
+    # preferable to setting this beforehand, in which case alteration to
+    # field values during post-init combined with post-init accessing the
+    # hash code would result in silent bugs.
+    if cache_hash:
+        if frozen:
+            if slots:
+                # if frozen and slots, then _setattr defined above
+                init_hash_cache = "_setattr('%s', %s)"
+            else:
+                # if frozen and not slots, then _inst_dict defined above
+                init_hash_cache = "_inst_dict['%s'] = %s"
+        else:
+            init_hash_cache = "self.%s = %s"
+        lines.append(init_hash_cache % (_hash_cache_field, "None"))
+
+    # For exceptions we rely on BaseException.__init__ for proper
+    # initialization.
+    if is_exc:
+        vals = ",".join("self." + a.name for a in attrs if a.init)
+
+        lines.append("BaseException.__init__(self, %s)" % (vals,))
+
+    args = ", ".join(args)
+    if kw_only_args:
+        if PY2:
+            raise PythonTooOldError(
+                "Keyword-only arguments only work on Python 3 and later."
+            )
+
+        args += "{leading_comma}*, {kw_only_args}".format(
+            leading_comma=", " if args else "",
+            kw_only_args=", ".join(kw_only_args),
+        )
+    return (
+        """\
+def __init__(self, {args}):
+    {lines}
+""".format(
+            args=args, lines="\n    ".join(lines) if lines else "pass"
+        ),
+        names_for_globals,
+        annotations,
+    )
+
+
+class Attribute(object):
+    """
+    *Read-only* representation of an attribute.
+
+    :attribute name: The name of the attribute.
+
+    Plus *all* arguments of `attr.ib` (except for ``factory``
+    which is only syntactic sugar for ``default=Factory(...)``.
+
+    For the version history of the fields, see `attr.ib`.
+    """
+
+    __slots__ = (
+        "name",
+        "default",
+        "validator",
+        "repr",
+        "eq",
+        "order",
+        "hash",
+        "init",
+        "metadata",
+        "type",
+        "converter",
+        "kw_only",
+    )
+
+    def __init__(
+        self,
+        name,
+        default,
+        validator,
+        repr,
+        cmp,  # XXX: unused, remove along with other cmp code.
+        hash,
+        init,
+        metadata=None,
+        type=None,
+        converter=None,
+        kw_only=False,
+        eq=None,
+        order=None,
+    ):
+        eq, order = _determine_eq_order(cmp, eq, order)
+
+        # Cache this descriptor here to speed things up later.
+        bound_setattr = _obj_setattr.__get__(self, Attribute)
+
+        # Despite the big red warning, people *do* instantiate `Attribute`
+        # themselves.
+        bound_setattr("name", name)
+        bound_setattr("default", default)
+        bound_setattr("validator", validator)
+        bound_setattr("repr", repr)
+        bound_setattr("eq", eq)
+        bound_setattr("order", order)
+        bound_setattr("hash", hash)
+        bound_setattr("init", init)
+        bound_setattr("converter", converter)
+        bound_setattr(
+            "metadata",
+            (
+                metadata_proxy(metadata)
+                if metadata
+                else _empty_metadata_singleton
+            ),
+        )
+        bound_setattr("type", type)
+        bound_setattr("kw_only", kw_only)
+
+    def __setattr__(self, name, value):
+        raise FrozenInstanceError()
+
+    @classmethod
+    def from_counting_attr(cls, name, ca, type=None):
+        # type holds the annotated value. deal with conflicts:
+        if type is None:
+            type = ca.type
+        elif ca.type is not None:
+            raise ValueError(
+                "Type annotation and type argument cannot both be present"
+            )
+        inst_dict = {
+            k: getattr(ca, k)
+            for k in Attribute.__slots__
+            if k
+            not in (
+                "name",
+                "validator",
+                "default",
+                "type",
+            )  # exclude methods and deprecated alias
+        }
+        return cls(
+            name=name,
+            validator=ca._validator,
+            default=ca._default,
+            type=type,
+            cmp=None,
+            **inst_dict
+        )
+
+    @property
+    def cmp(self):
+        """
+        Simulate the presence of a cmp attribute and warn.
+        """
+        warnings.warn(_CMP_DEPRECATION, DeprecationWarning, stacklevel=2)
+
+        return self.eq and self.order
+
+    # Don't use attr.assoc since fields(Attribute) doesn't work
+    def _assoc(self, **changes):
+        """
+        Copy *self* and apply *changes*.
+        """
+        new = copy.copy(self)
+
+        new._setattrs(changes.items())
+
+        return new
+
+    # Don't use _add_pickle since fields(Attribute) doesn't work
+    def __getstate__(self):
+        """
+        Play nice with pickle.
+        """
+        return tuple(
+            getattr(self, name) if name != "metadata" else dict(self.metadata)
+            for name in self.__slots__
+        )
+
+    def __setstate__(self, state):
+        """
+        Play nice with pickle.
+        """
+        self._setattrs(zip(self.__slots__, state))
+
+    def _setattrs(self, name_values_pairs):
+        bound_setattr = _obj_setattr.__get__(self, Attribute)
+        for name, value in name_values_pairs:
+            if name != "metadata":
+                bound_setattr(name, value)
+            else:
+                bound_setattr(
+                    name,
+                    metadata_proxy(value)
+                    if value
+                    else _empty_metadata_singleton,
+                )
+
+
+_a = [
+    Attribute(
+        name=name,
+        default=NOTHING,
+        validator=None,
+        repr=True,
+        cmp=None,
+        eq=True,
+        order=False,
+        hash=(name != "metadata"),
+        init=True,
+    )
+    for name in Attribute.__slots__
+]
+
+Attribute = _add_hash(
+    _add_eq(_add_repr(Attribute, attrs=_a), attrs=_a),
+    attrs=[a for a in _a if a.hash],
+)
+
+
+class _CountingAttr(object):
+    """
+    Intermediate representation of attributes that uses a counter to preserve
+    the order in which the attributes have been defined.
+
+    *Internal* data structure of the attrs library.  Running into is most
+    likely the result of a bug like a forgotten `@attr.s` decorator.
+    """
+
+    __slots__ = (
+        "counter",
+        "_default",
+        "repr",
+        "eq",
+        "order",
+        "hash",
+        "init",
+        "metadata",
+        "_validator",
+        "converter",
+        "type",
+        "kw_only",
+    )
+    __attrs_attrs__ = tuple(
+        Attribute(
+            name=name,
+            default=NOTHING,
+            validator=None,
+            repr=True,
+            cmp=None,
+            hash=True,
+            init=True,
+            kw_only=False,
+            eq=True,
+            order=False,
+        )
+        for name in (
+            "counter",
+            "_default",
+            "repr",
+            "eq",
+            "order",
+            "hash",
+            "init",
+        )
+    ) + (
+        Attribute(
+            name="metadata",
+            default=None,
+            validator=None,
+            repr=True,
+            cmp=None,
+            hash=False,
+            init=True,
+            kw_only=False,
+            eq=True,
+            order=False,
+        ),
+    )
+    cls_counter = 0
+
+    def __init__(
+        self,
+        default,
+        validator,
+        repr,
+        cmp,  # XXX: unused, remove along with cmp
+        hash,
+        init,
+        converter,
+        metadata,
+        type,
+        kw_only,
+        eq,
+        order,
+    ):
+        _CountingAttr.cls_counter += 1
+        self.counter = _CountingAttr.cls_counter
+        self._default = default
+        # If validator is a list/tuple, wrap it using helper validator.
+        if validator and isinstance(validator, (list, tuple)):
+            self._validator = and_(*validator)
+        else:
+            self._validator = validator
+        self.repr = repr
+        self.eq = eq
+        self.order = order
+        self.hash = hash
+        self.init = init
+        self.converter = converter
+        self.metadata = metadata
+        self.type = type
+        self.kw_only = kw_only
+
+    def validator(self, meth):
+        """
+        Decorator that adds *meth* to the list of validators.
+
+        Returns *meth* unchanged.
+
+        .. versionadded:: 17.1.0
+        """
+        if self._validator is None:
+            self._validator = meth
+        else:
+            self._validator = and_(self._validator, meth)
+        return meth
+
+    def default(self, meth):
+        """
+        Decorator that allows to set the default for an attribute.
+
+        Returns *meth* unchanged.
+
+        :raises DefaultAlreadySetError: If default has been set before.
+
+        .. versionadded:: 17.1.0
+        """
+        if self._default is not NOTHING:
+            raise DefaultAlreadySetError()
+
+        self._default = Factory(meth, takes_self=True)
+
+        return meth
+
+
+_CountingAttr = _add_eq(_add_repr(_CountingAttr))
+
+
+@attrs(slots=True, init=False, hash=True)
+class Factory(object):
+    """
+    Stores a factory callable.
+
+    If passed as the default value to `attr.ib`, the factory is used to
+    generate a new value.
+
+    :param callable factory: A callable that takes either none or exactly one
+        mandatory positional argument depending on *takes_self*.
+    :param bool takes_self: Pass the partially initialized instance that is
+        being initialized as a positional argument.
+
+    .. versionadded:: 17.1.0  *takes_self*
+    """
+
+    factory = attrib()
+    takes_self = attrib()
+
+    def __init__(self, factory, takes_self=False):
+        """
+        `Factory` is part of the default machinery so if we want a default
+        value here, we have to implement it ourselves.
+        """
+        self.factory = factory
+        self.takes_self = takes_self
+
+
+def make_class(name, attrs, bases=(object,), **attributes_arguments):
+    """
+    A quick way to create a new class called *name* with *attrs*.
+
+    :param name: The name for the new class.
+    :type name: str
+
+    :param attrs: A list of names or a dictionary of mappings of names to
+        attributes.
+
+        If *attrs* is a list or an ordered dict (`dict` on Python 3.6+,
+        `collections.OrderedDict` otherwise), the order is deduced from
+        the order of the names or attributes inside *attrs*.  Otherwise the
+        order of the definition of the attributes is used.
+    :type attrs: `list` or `dict`
+
+    :param tuple bases: Classes that the new class will subclass.
+
+    :param attributes_arguments: Passed unmodified to `attr.s`.
+
+    :return: A new class with *attrs*.
+    :rtype: type
+
+    .. versionadded:: 17.1.0 *bases*
+    .. versionchanged:: 18.1.0 If *attrs* is ordered, the order is retained.
+    """
+    if isinstance(attrs, dict):
+        cls_dict = attrs
+    elif isinstance(attrs, (list, tuple)):
+        cls_dict = dict((a, attrib()) for a in attrs)
+    else:
+        raise TypeError("attrs argument must be a dict or a list.")
+
+    post_init = cls_dict.pop("__attrs_post_init__", None)
+    type_ = type(
+        name,
+        bases,
+        {} if post_init is None else {"__attrs_post_init__": post_init},
+    )
+    # For pickling to work, the __module__ variable needs to be set to the
+    # frame where the class is created.  Bypass this step in environments where
+    # sys._getframe is not defined (Jython for example) or sys._getframe is not
+    # defined for arguments greater than 0 (IronPython).
+    try:
+        type_.__module__ = sys._getframe(1).f_globals.get(
+            "__name__", "__main__"
+        )
+    except (AttributeError, ValueError):
+        pass
+
+    # We do it here for proper warnings with meaningful stacklevel.
+    cmp = attributes_arguments.pop("cmp", None)
+    attributes_arguments["eq"], attributes_arguments[
+        "order"
+    ] = _determine_eq_order(
+        cmp, attributes_arguments.get("eq"), attributes_arguments.get("order")
+    )
+
+    return _attrs(these=cls_dict, **attributes_arguments)(type_)
+
+
+# These are required by within this module so we define them here and merely
+# import into .validators.
+
+
+@attrs(slots=True, hash=True)
+class _AndValidator(object):
+    """
+    Compose many validators to a single one.
+    """
+
+    _validators = attrib()
+
+    def __call__(self, inst, attr, value):
+        for v in self._validators:
+            v(inst, attr, value)
+
+
+def and_(*validators):
+    """
+    A validator that composes multiple validators into one.
+
+    When called on a value, it runs all wrapped validators.
+
+    :param validators: Arbitrary number of validators.
+    :type validators: callables
+
+    .. versionadded:: 17.1.0
+    """
+    vals = []
+    for validator in validators:
+        vals.extend(
+            validator._validators
+            if isinstance(validator, _AndValidator)
+            else [validator]
+        )
+
+    return _AndValidator(tuple(vals))
diff --git a/third_party/python/attrs/attr/_version.py b/third_party/python/attrs/attr/_version.py
new file mode 100644
index 0000000000..014e78a1b4
--- /dev/null
+++ b/third_party/python/attrs/attr/_version.py
@@ -0,0 +1,85 @@
+from __future__ import absolute_import, division, print_function
+
+from functools import total_ordering
+
+from ._funcs import astuple
+from ._make import attrib, attrs
+
+
+@total_ordering
+@attrs(eq=False, order=False, slots=True, frozen=True)
+class VersionInfo(object):
+    """
+    A version object that can be compared to tuple of length 1--4:
+
+    >>> attr.VersionInfo(19, 1, 0, "final")  <= (19, 2)
+    True
+    >>> attr.VersionInfo(19, 1, 0, "final") < (19, 1, 1)
+    True
+    >>> vi = attr.VersionInfo(19, 2, 0, "final")
+    >>> vi < (19, 1, 1)
+    False
+    >>> vi < (19,)
+    False
+    >>> vi == (19, 2,)
+    True
+    >>> vi == (19, 2, 1)
+    False
+
+    .. versionadded:: 19.2
+    """
+
+    year = attrib(type=int)
+    minor = attrib(type=int)
+    micro = attrib(type=int)
+    releaselevel = attrib(type=str)
+
+    @classmethod
+    def _from_version_string(cls, s):
+        """
+        Parse *s* and return a _VersionInfo.
+        """
+        v = s.split(".")
+        if len(v) == 3:
+            v.append("final")
+
+        return cls(
+            year=int(v[0]), minor=int(v[1]), micro=int(v[2]), releaselevel=v[3]
+        )
+
+    def _ensure_tuple(self, other):
+        """
+        Ensure *other* is a tuple of a valid length.
+
+        Returns a possibly transformed *other* and ourselves as a tuple of
+        the same length as *other*.
+        """
+
+        if self.__class__ is other.__class__:
+            other = astuple(other)
+
+        if not isinstance(other, tuple):
+            raise NotImplementedError
+
+        if not (1 <= len(other) <= 4):
+            raise NotImplementedError
+
+        return astuple(self)[: len(other)], other
+
+    def __eq__(self, other):
+        try:
+            us, them = self._ensure_tuple(other)
+        except NotImplementedError:
+            return NotImplemented
+
+        return us == them
+
+    def __lt__(self, other):
+        try:
+            us, them = self._ensure_tuple(other)
+        except NotImplementedError:
+            return NotImplemented
+
+        # Since alphabetically "dev0" < "final" < "post1" < "post2", we don't
+        # have to do anything special with releaselevel for now.
+        return us < them
diff --git a/third_party/python/attrs/attr/_version.pyi b/third_party/python/attrs/attr/_version.pyi
new file mode 100644
index 0000000000..45ced08633
--- /dev/null
+++ b/third_party/python/attrs/attr/_version.pyi
@@ -0,0 +1,9 @@
+class VersionInfo:
+    @property
+    def year(self) -> int: ...
+    @property
+    def minor(self) -> int: ...
+    @property
+    def micro(self) -> int: ...
+    @property
+    def releaselevel(self) -> str: ...
diff --git a/third_party/python/attrs/attr/converters.py b/third_party/python/attrs/attr/converters.py
new file mode 100644
index 0000000000..8592897847
--- /dev/null
+++ b/third_party/python/attrs/attr/converters.py
@@ -0,0 +1,78 @@
+"""
+Commonly useful converters.
+"""
+
+from __future__ import absolute_import, division, print_function
+
+from ._make import NOTHING, Factory
+
+
+def optional(converter):
+    """
+    A converter that allows an attribute to be optional. An optional attribute
+    is one which can be set to ``None``.
+
+    :param callable converter: the converter that is used for non-``None``
+        values.
+
+    .. versionadded:: 17.1.0
+    """
+
+    def optional_converter(val):
+        if val is None:
+            return None
+        return converter(val)
+
+    return optional_converter
+
+
+def default_if_none(default=NOTHING, factory=None):
+    """
+    A converter that allows to replace ``None`` values by *default* or the
+    result of *factory*.
+
+    :param default: Value to be used if ``None`` is passed. Passing an instance
+       of `attr.Factory` is supported, however the ``takes_self`` option
+       is *not*.
+    :param callable factory: A callable that takes not parameters whose result
+       is used if ``None`` is passed.
+
+    :raises TypeError: If **neither** *default* or *factory* is passed.
+    :raises TypeError: If **both** *default* and *factory* are passed.
+    :raises ValueError: If an instance of `attr.Factory` is passed with
+       ``takes_self=True``.
+
+    .. versionadded:: 18.2.0
+    """
+    if default is NOTHING and factory is None:
+        raise TypeError("Must pass either `default` or `factory`.")
+
+    if default is not NOTHING and factory is not None:
+        raise TypeError(
+            "Must pass either `default` or `factory` but not both."
+        )
+
+    if factory is not None:
+        default = Factory(factory)
+
+    if isinstance(default, Factory):
+        if default.takes_self:
+            raise ValueError(
+                "`takes_self` is not supported by default_if_none."
+            )
+
+        def default_if_none_converter(val):
+            if val is not None:
+                return val
+
+            return default.factory()
+
+    else:
+
+        def default_if_none_converter(val):
+            if val is not None:
+                return val
+
+            return default
+
+    return default_if_none_converter
diff --git a/third_party/python/attrs/attr/converters.pyi b/third_party/python/attrs/attr/converters.pyi
new file mode 100644
index 0000000000..63b2a3866e
--- /dev/null
+++ b/third_party/python/attrs/attr/converters.pyi
@@ -0,0 +1,12 @@
+from typing import TypeVar, Optional, Callable, overload
+from . import _ConverterType
+
+_T = TypeVar("_T")
+
+def optional(
+    converter: _ConverterType[_T]
+) -> _ConverterType[Optional[_T]]: ...
+@overload
+def default_if_none(default: _T) -> _ConverterType[_T]: ...
+@overload
+def default_if_none(*, factory: Callable[[], _T]) -> _ConverterType[_T]: ...
diff --git a/third_party/python/attrs/attr/exceptions.py b/third_party/python/attrs/attr/exceptions.py
new file mode 100644
index 0000000000..d1b76185c9
--- /dev/null
+++ b/third_party/python/attrs/attr/exceptions.py
@@ -0,0 +1,74 @@
+from __future__ import absolute_import, division, print_function
+
+
+class FrozenInstanceError(AttributeError):
+    """
+    A frozen/immutable instance has been attempted to be modified.
+
+    It mirrors the behavior of ``namedtuples`` by using the same error message
+    and subclassing `AttributeError`.
+
+    .. versionadded:: 16.1.0
+    """
+
+    msg = "can't set attribute"
+    args = [msg]
+
+
+class AttrsAttributeNotFoundError(ValueError):
+    """
+    An ``attrs`` function couldn't find an attribute that the user asked for.
+
+    .. versionadded:: 16.2.0
+    """
+
+
+class NotAnAttrsClassError(ValueError):
+    """
+    A non-``attrs`` class has been passed into an ``attrs`` function.
+
+    .. versionadded:: 16.2.0
+    """
+
+
+class DefaultAlreadySetError(RuntimeError):
+    """
+    A default has been set using ``attr.ib()`` and is attempted to be reset
+    using the decorator.
+
+    .. versionadded:: 17.1.0
+    """
+
+
+class UnannotatedAttributeError(RuntimeError):
+    """
+    A class with ``auto_attribs=True`` has an ``attr.ib()`` without a type
+    annotation.
+
+    .. versionadded:: 17.3.0
+    """
+
+
+class PythonTooOldError(RuntimeError):
+    """
+    An ``attrs`` feature requiring a more recent python version has been used.
+
+    .. versionadded:: 18.2.0
+    """
+
+
+class NotCallableError(TypeError):
+    """
+    A ``attr.ib()`` requiring a callable has been set with a value
+    that is not callable.
+
+    .. versionadded:: 19.2.0
+    """
+
+    def __init__(self, msg, value):
+        super(TypeError, self).__init__(msg, value)
+        self.msg = msg
+        self.value = value
+
+    def __str__(self):
+        return str(self.msg)
diff --git a/third_party/python/attrs/attr/exceptions.pyi b/third_party/python/attrs/attr/exceptions.pyi
new file mode 100644
index 0000000000..736fde2e1d
--- /dev/null
+++ b/third_party/python/attrs/attr/exceptions.pyi
@@ -0,0 +1,15 @@
+from typing import Any
+
+class FrozenInstanceError(AttributeError):
+    msg: str = ...
+
+class AttrsAttributeNotFoundError(ValueError): ...
+class NotAnAttrsClassError(ValueError): ...
+class DefaultAlreadySetError(RuntimeError): ...
+class UnannotatedAttributeError(RuntimeError): ...
+class PythonTooOldError(RuntimeError): ...
+
+class NotCallableError(TypeError):
+    msg: str = ...
+    value: Any = ...
+    def __init__(self, msg: str, value: Any) -> None: ...
diff --git a/third_party/python/attrs/attr/filters.py b/third_party/python/attrs/attr/filters.py
new file mode 100644
index 0000000000..dc47e8fa38
--- /dev/null
+++ b/third_party/python/attrs/attr/filters.py
@@ -0,0 +1,52 @@
+"""
+Commonly useful filters for `attr.asdict`.
+"""
+
+from __future__ import absolute_import, division, print_function
+
+from ._compat import isclass
+from ._make import Attribute
+
+
+def _split_what(what):
+    """
+    Returns a tuple of `frozenset`s of classes and attributes.
+    """
+    return (
+        frozenset(cls for cls in what if isclass(cls)),
+        frozenset(cls for cls in what if isinstance(cls, Attribute)),
+    )
+
+
+def include(*what):
+    """
+    Whitelist *what*.
+
+    :param what: What to whitelist.
+    :type what: `list` of `type` or `attr.Attribute`\\ s
+
+    :rtype: `callable`
+    """
+    cls, attrs = _split_what(what)
+
+    def include_(attribute, value):
+        return value.__class__ in cls or attribute in attrs
+
+    return include_
+
+
+def exclude(*what):
+    """
+    Blacklist *what*.
+
+    :param what: What to blacklist.
+    :type what: `list` of classes or `attr.Attribute`\\ s.
+
+    :rtype: `callable`
+    """
+    cls, attrs = _split_what(what)
+
+    def exclude_(attribute, value):
+        return value.__class__ not in cls and attribute not in attrs
+
+    return exclude_
diff --git a/third_party/python/attrs/attr/filters.pyi b/third_party/python/attrs/attr/filters.pyi
new file mode 100644
index 0000000000..68368fe2b9
--- /dev/null
+++ b/third_party/python/attrs/attr/filters.pyi
@@ -0,0 +1,5 @@
+from typing import Union, Any
+from . import Attribute, _FilterType
+
+def include(*what: Union[type, Attribute[Any]]) -> _FilterType[Any]: ...
+def exclude(*what: Union[type, Attribute[Any]]) -> _FilterType[Any]: ...
diff --git a/third_party/python/attrs/attr/py.typed b/third_party/python/attrs/attr/py.typed
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/third_party/python/attrs/attr/py.typed
diff --git a/third_party/python/attrs/attr/validators.py b/third_party/python/attrs/attr/validators.py
new file mode 100644
index 0000000000..839d310c38
--- /dev/null
+++ b/third_party/python/attrs/attr/validators.py
@@ -0,0 +1,378 @@
+"""
+Commonly useful validators.
+"""
+
+from __future__ import absolute_import, division, print_function
+
+import re
+
+from ._make import _AndValidator, and_, attrib, attrs
+from .exceptions import NotCallableError
+
+
+__all__ = [
+    "and_",
+    "deep_iterable",
+    "deep_mapping",
+    "in_",
+    "instance_of",
+    "is_callable",
+    "matches_re",
+    "optional",
+    "provides",
+]
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _InstanceOfValidator(object):
+    type = attrib()
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not isinstance(value, self.type):
+            raise TypeError(
+                "'{name}' must be {type!r} (got {value!r} that is a "
+                "{actual!r}).".format(
+                    name=attr.name,
+                    type=self.type,
+                    actual=value.__class__,
+                    value=value,
+                ),
+                attr,
+                self.type,
+                value,
+            )
+
+    def __repr__(self):
+        return "<instance_of validator for type {type!r}>".format(
+            type=self.type
+        )
+
+
+def instance_of(type):
+    """
+    A validator that raises a `TypeError` if the initializer is called
+    with a wrong type for this particular attribute (checks are performed using
+    `isinstance` therefore it's also valid to pass a tuple of types).
+
+    :param type: The type to check for.
+    :type type: type or tuple of types
+
+    :raises TypeError: With a human readable error message, the attribute
+        (of type `attr.Attribute`), the expected type, and the value it
+        got.
+    """
+    return _InstanceOfValidator(type)
+
+
+@attrs(repr=False, frozen=True)
+class _MatchesReValidator(object):
+    regex = attrib()
+    flags = attrib()
+    match_func = attrib()
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not self.match_func(value):
+            raise ValueError(
+                "'{name}' must match regex {regex!r}"
+                " ({value!r} doesn't)".format(
+                    name=attr.name, regex=self.regex.pattern, value=value
+                ),
+                attr,
+                self.regex,
+                value,
+            )
+
+    def __repr__(self):
+        return "<matches_re validator for pattern {regex!r}>".format(
+            regex=self.regex
+        )
+
+
+def matches_re(regex, flags=0, func=None):
+    r"""
+    A validator that raises `ValueError` if the initializer is called
+    with a string that doesn't match *regex*.
+
+    :param str regex: a regex string to match against
+    :param int flags: flags that will be passed to the underlying re function
+        (default 0)
+    :param callable func: which underlying `re` function to call (options
+        are `re.fullmatch`, `re.search`, `re.match`, default
+        is ``None`` which means either `re.fullmatch` or an emulation of
+        it on Python 2). For performance reasons, they won't be used directly
+        but on a pre-`re.compile`\ ed pattern.
+
+    .. versionadded:: 19.2.0
+    """
+    fullmatch = getattr(re, "fullmatch", None)
+    valid_funcs = (fullmatch, None, re.search, re.match)
+    if func not in valid_funcs:
+        raise ValueError(
+            "'func' must be one of %s."
+            % (
+                ", ".join(
+                    sorted(
+                        e and e.__name__ or "None" for e in set(valid_funcs)
+                    )
+                ),
+            )
+        )
+
+    pattern = re.compile(regex, flags)
+    if func is re.match:
+        match_func = pattern.match
+    elif func is re.search:
+        match_func = pattern.search
+    else:
+        if fullmatch:
+            match_func = pattern.fullmatch
+        else:
+            pattern = re.compile(r"(?:{})\Z".format(regex), flags)
+            match_func = pattern.match
+
+    return _MatchesReValidator(pattern, flags, match_func)
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _ProvidesValidator(object):
+    interface = attrib()
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not self.interface.providedBy(value):
+            raise TypeError(
+                "'{name}' must provide {interface!r} which {value!r} "
+                "doesn't.".format(
+                    name=attr.name, interface=self.interface, value=value
+                ),
+                attr,
+                self.interface,
+                value,
+            )
+
+    def __repr__(self):
+        return "<provides validator for interface {interface!r}>".format(
+            interface=self.interface
+        )
+
+
+def provides(interface):
+    """
+    A validator that raises a `TypeError` if the initializer is called
+    with an object that does not provide the requested *interface* (checks are
+    performed using ``interface.providedBy(value)`` (see `zope.interface
+    <https://zopeinterface.readthedocs.io/en/latest/>`_).
+
+    :param zope.interface.Interface interface: The interface to check for.
+
+    :raises TypeError: With a human readable error message, the attribute
+        (of type `attr.Attribute`), the expected interface, and the
+        value it got.
+    """
+    return _ProvidesValidator(interface)
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _OptionalValidator(object):
+    validator = attrib()
+
+    def __call__(self, inst, attr, value):
+        if value is None:
+            return
+
+        self.validator(inst, attr, value)
+
+    def __repr__(self):
+        return "<optional validator for {what} or None>".format(
+            what=repr(self.validator)
+        )
+
+
+def optional(validator):
+    """
+    A validator that makes an attribute optional.  An optional attribute is one
+    which can be set to ``None`` in addition to satisfying the requirements of
+    the sub-validator.
+
+    :param validator: A validator (or a list of validators) that is used for
+        non-``None`` values.
+    :type validator: callable or `list` of callables.
+
+    .. versionadded:: 15.1.0
+    .. versionchanged:: 17.1.0 *validator* can be a list of validators.
+    """
+    if isinstance(validator, list):
+        return _OptionalValidator(_AndValidator(validator))
+    return _OptionalValidator(validator)
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _InValidator(object):
+    options = attrib()
+
+    def __call__(self, inst, attr, value):
+        try:
+            in_options = value in self.options
+        except TypeError:  # e.g. `1 in "abc"`
+            in_options = False
+
+        if not in_options:
+            raise ValueError(
+                "'{name}' must be in {options!r} (got {value!r})".format(
+                    name=attr.name, options=self.options, value=value
+                )
+            )
+
+    def __repr__(self):
+        return "<in_ validator with options {options!r}>".format(
+            options=self.options
+        )
+
+
+def in_(options):
+    """
+    A validator that raises a `ValueError` if the initializer is called
+    with a value that does not belong in the options provided.  The check is
+    performed using ``value in options``.
+
+    :param options: Allowed options.
+    :type options: list, tuple, `enum.Enum`, ...
+
+    :raises ValueError: With a human readable error message, the attribute (of
+       type `attr.Attribute`), the expected options, and the value it
+       got.
+
+    .. versionadded:: 17.1.0
+    """
+    return _InValidator(options)
+
+
+@attrs(repr=False, slots=False, hash=True)
+class _IsCallableValidator(object):
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if not callable(value):
+            message = (
+                "'{name}' must be callable "
+                "(got {value!r} that is a {actual!r})."
+            )
+            raise NotCallableError(
+                msg=message.format(
+                    name=attr.name, value=value, actual=value.__class__
+                ),
+                value=value,
+            )
+
+    def __repr__(self):
+        return "<is_callable validator>"
+
+
+def is_callable():
+    """
+    A validator that raises a `attr.exceptions.NotCallableError` if the
+    initializer is called with a value for this particular attribute
+    that is not callable.
+
+    .. versionadded:: 19.1.0
+
+    :raises `attr.exceptions.NotCallableError`: With a human readable error
+        message containing the attribute (`attr.Attribute`) name,
+        and the value it got.
+    """
+    return _IsCallableValidator()
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _DeepIterable(object):
+    member_validator = attrib(validator=is_callable())
+    iterable_validator = attrib(
+        default=None, validator=optional(is_callable())
+    )
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if self.iterable_validator is not None:
+            self.iterable_validator(inst, attr, value)
+
+        for member in value:
+            self.member_validator(inst, attr, member)
+
+    def __repr__(self):
+        iterable_identifier = (
+            ""
+            if self.iterable_validator is None
+            else " {iterable!r}".format(iterable=self.iterable_validator)
+        )
+        return (
+            "<deep_iterable validator for{iterable_identifier}"
+            " iterables of {member!r}>"
+        ).format(
+            iterable_identifier=iterable_identifier,
+            member=self.member_validator,
+        )
+
+
+def deep_iterable(member_validator, iterable_validator=None):
+    """
+    A validator that performs deep validation of an iterable.
+
+    :param member_validator: Validator to apply to iterable members
+    :param iterable_validator: Validator to apply to iterable itself
+        (optional)
+
+    .. versionadded:: 19.1.0
+
+    :raises TypeError: if any sub-validators fail
+    """
+    return _DeepIterable(member_validator, iterable_validator)
+
+
+@attrs(repr=False, slots=True, hash=True)
+class _DeepMapping(object):
+    key_validator = attrib(validator=is_callable())
+    value_validator = attrib(validator=is_callable())
+    mapping_validator = attrib(default=None, validator=optional(is_callable()))
+
+    def __call__(self, inst, attr, value):
+        """
+        We use a callable class to be able to change the ``__repr__``.
+        """
+        if self.mapping_validator is not None:
+            self.mapping_validator(inst, attr, value)
+
+        for key in value:
+            self.key_validator(inst, attr, key)
+            self.value_validator(inst, attr, value[key])
+
+    def __repr__(self):
+        return (
+            "<deep_mapping validator for objects mapping {key!r} to {value!r}>"
+        ).format(key=self.key_validator, value=self.value_validator)
+
+
+def deep_mapping(key_validator, value_validator, mapping_validator=None):
+    """
+    A validator that performs deep validation of a dictionary.
+
+    :param key_validator: Validator to apply to dictionary keys
+    :param value_validator: Validator to apply to dictionary values
+    :param mapping_validator: Validator to apply to top-level mapping
+        attribute (optional)
+
+    .. versionadded:: 19.1.0
+
+    :raises TypeError: if any sub-validators fail
+    """
+    return _DeepMapping(key_validator, value_validator, mapping_validator)
diff --git a/third_party/python/attrs/attr/validators.pyi b/third_party/python/attrs/attr/validators.pyi
new file mode 100644
index 0000000000..9a22abb197
--- /dev/null
+++ b/third_party/python/attrs/attr/validators.pyi
@@ -0,0 +1,66 @@
+from typing import (
+    Container,
+    List,
+    Union,
+    TypeVar,
+    Type,
+    Any,
+    Optional,
+    Tuple,
+    Iterable,
+    Mapping,
+    Callable,
+    Match,
+    AnyStr,
+    overload,
+)
+from . import _ValidatorType
+
+_T = TypeVar("_T")
+_T1 = TypeVar("_T1")
+_T2 = TypeVar("_T2")
+_T3 = TypeVar("_T3")
+_I = TypeVar("_I", bound=Iterable)
+_K = TypeVar("_K")
+_V = TypeVar("_V")
+_M = TypeVar("_M", bound=Mapping)
+
+# To be more precise on instance_of use some overloads.
+# If there are more than 3 items in the tuple then we fall back to Any
+@overload
+def instance_of(type: Type[_T]) -> _ValidatorType[_T]: ...
+@overload
+def instance_of(type: Tuple[Type[_T]]) -> _ValidatorType[_T]: ...
+@overload
+def instance_of(
+    type: Tuple[Type[_T1], Type[_T2]]
+) -> _ValidatorType[Union[_T1, _T2]]: ...
+@overload
+def instance_of(
+    type: Tuple[Type[_T1], Type[_T2], Type[_T3]]
+) -> _ValidatorType[Union[_T1, _T2, _T3]]: ...
+@overload
+def instance_of(type: Tuple[type, ...]) -> _ValidatorType[Any]: ...
+def provides(interface: Any) -> _ValidatorType[Any]: ...
+def optional(
+    validator: Union[_ValidatorType[_T], List[_ValidatorType[_T]]]
+) -> _ValidatorType[Optional[_T]]: ...
+def in_(options: Container[_T]) -> _ValidatorType[_T]: ...
+def and_(*validators: _ValidatorType[_T]) -> _ValidatorType[_T]: ...
+def matches_re(
+    regex: AnyStr,
+    flags: int = ...,
+    func: Optional[
+        Callable[[AnyStr, AnyStr, int], Optional[Match[AnyStr]]]
+    ] = ...,
+) -> _ValidatorType[AnyStr]: ...
+def deep_iterable(
+    member_validator: _ValidatorType[_T],
+    iterable_validator: Optional[_ValidatorType[_I]] = ...,
+) -> _ValidatorType[_I]: ...
+def deep_mapping(
+    key_validator: _ValidatorType[_K],
+    value_validator: _ValidatorType[_V],
+    mapping_validator: Optional[_ValidatorType[_M]] = ...,
+) -> _ValidatorType[_M]: ...
+def is_callable() -> _ValidatorType[_T]: ...