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Diffstat (limited to 'third_party/python/attrs/attr/_make.py')
| -rw-r--r-- | third_party/python/attrs/attr/_make.py | 2168 |
1 files changed, 2168 insertions, 0 deletions
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)) |