Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 1053 insertions, 0 deletions

diff --git a/third_party/python/Jinja2/jinja2/runtime.py b/third_party/python/Jinja2/jinja2/runtime.py
new file mode 100644
index 0000000000..985842b284
--- /dev/null
+++ b/third_party/python/Jinja2/jinja2/runtime.py
@@ -0,0 +1,1053 @@
+"""The runtime functions and state used by compiled templates."""
+import functools
+import sys
+import typing as t
+from collections import abc
+from itertools import chain
+
+from markupsafe import escape  # noqa: F401
+from markupsafe import Markup
+from markupsafe import soft_str
+
+from .async_utils import auto_aiter
+from .async_utils import auto_await  # noqa: F401
+from .exceptions import TemplateNotFound  # noqa: F401
+from .exceptions import TemplateRuntimeError  # noqa: F401
+from .exceptions import UndefinedError
+from .nodes import EvalContext
+from .utils import _PassArg
+from .utils import concat
+from .utils import internalcode
+from .utils import missing
+from .utils import Namespace  # noqa: F401
+from .utils import object_type_repr
+from .utils import pass_eval_context
+
+V = t.TypeVar("V")
+F = t.TypeVar("F", bound=t.Callable[..., t.Any])
+
+if t.TYPE_CHECKING:
+    import logging
+    import typing_extensions as te
+    from .environment import Environment
+
+    class LoopRenderFunc(te.Protocol):
+        def __call__(
+            self,
+            reciter: t.Iterable[V],
+            loop_render_func: "LoopRenderFunc",
+            depth: int = 0,
+        ) -> str:
+            ...
+
+
+# these variables are exported to the template runtime
+exported = [
+    "LoopContext",
+    "TemplateReference",
+    "Macro",
+    "Markup",
+    "TemplateRuntimeError",
+    "missing",
+    "escape",
+    "markup_join",
+    "str_join",
+    "identity",
+    "TemplateNotFound",
+    "Namespace",
+    "Undefined",
+    "internalcode",
+]
+async_exported = [
+    "AsyncLoopContext",
+    "auto_aiter",
+    "auto_await",
+]
+
+
+def identity(x: V) -> V:
+    """Returns its argument. Useful for certain things in the
+    environment.
+    """
+    return x
+
+
+def markup_join(seq: t.Iterable[t.Any]) -> str:
+    """Concatenation that escapes if necessary and converts to string."""
+    buf = []
+    iterator = map(soft_str, seq)
+    for arg in iterator:
+        buf.append(arg)
+        if hasattr(arg, "__html__"):
+            return Markup("").join(chain(buf, iterator))
+    return concat(buf)
+
+
+def str_join(seq: t.Iterable[t.Any]) -> str:
+    """Simple args to string conversion and concatenation."""
+    return concat(map(str, seq))
+
+
+def new_context(
+    environment: "Environment",
+    template_name: t.Optional[str],
+    blocks: t.Dict[str, t.Callable[["Context"], t.Iterator[str]]],
+    vars: t.Optional[t.Dict[str, t.Any]] = None,
+    shared: bool = False,
+    globals: t.Optional[t.MutableMapping[str, t.Any]] = None,
+    locals: t.Optional[t.Mapping[str, t.Any]] = None,
+) -> "Context":
+    """Internal helper for context creation."""
+    if vars is None:
+        vars = {}
+    if shared:
+        parent = vars
+    else:
+        parent = dict(globals or (), **vars)
+    if locals:
+        # if the parent is shared a copy should be created because
+        # we don't want to modify the dict passed
+        if shared:
+            parent = dict(parent)
+        for key, value in locals.items():
+            if value is not missing:
+                parent[key] = value
+    return environment.context_class(
+        environment, parent, template_name, blocks, globals=globals
+    )
+
+
+class TemplateReference:
+    """The `self` in templates."""
+
+    def __init__(self, context: "Context") -> None:
+        self.__context = context
+
+    def __getitem__(self, name: str) -> t.Any:
+        blocks = self.__context.blocks[name]
+        return BlockReference(name, self.__context, blocks, 0)
+
+    def __repr__(self) -> str:
+        return f"<{type(self).__name__} {self.__context.name!r}>"
+
+
+def _dict_method_all(dict_method: F) -> F:
+    @functools.wraps(dict_method)
+    def f_all(self: "Context") -> t.Any:
+        return dict_method(self.get_all())
+
+    return t.cast(F, f_all)
+
+
+@abc.Mapping.register
+class Context:
+    """The template context holds the variables of a template.  It stores the
+    values passed to the template and also the names the template exports.
+    Creating instances is neither supported nor useful as it's created
+    automatically at various stages of the template evaluation and should not
+    be created by hand.
+
+    The context is immutable.  Modifications on :attr:`parent` **must not**
+    happen and modifications on :attr:`vars` are allowed from generated
+    template code only.  Template filters and global functions marked as
+    :func:`pass_context` get the active context passed as first argument
+    and are allowed to access the context read-only.
+
+    The template context supports read only dict operations (`get`,
+    `keys`, `values`, `items`, `iterkeys`, `itervalues`, `iteritems`,
+    `__getitem__`, `__contains__`).  Additionally there is a :meth:`resolve`
+    method that doesn't fail with a `KeyError` but returns an
+    :class:`Undefined` object for missing variables.
+    """
+
+    def __init__(
+        self,
+        environment: "Environment",
+        parent: t.Dict[str, t.Any],
+        name: t.Optional[str],
+        blocks: t.Dict[str, t.Callable[["Context"], t.Iterator[str]]],
+        globals: t.Optional[t.MutableMapping[str, t.Any]] = None,
+    ):
+        self.parent = parent
+        self.vars: t.Dict[str, t.Any] = {}
+        self.environment: "Environment" = environment
+        self.eval_ctx = EvalContext(self.environment, name)
+        self.exported_vars: t.Set[str] = set()
+        self.name = name
+        self.globals_keys = set() if globals is None else set(globals)
+
+        # create the initial mapping of blocks.  Whenever template inheritance
+        # takes place the runtime will update this mapping with the new blocks
+        # from the template.
+        self.blocks = {k: [v] for k, v in blocks.items()}
+
+    def super(
+        self, name: str, current: t.Callable[["Context"], t.Iterator[str]]
+    ) -> t.Union["BlockReference", "Undefined"]:
+        """Render a parent block."""
+        try:
+            blocks = self.blocks[name]
+            index = blocks.index(current) + 1
+            blocks[index]
+        except LookupError:
+            return self.environment.undefined(
+                f"there is no parent block called {name!r}.", name="super"
+            )
+        return BlockReference(name, self, blocks, index)
+
+    def get(self, key: str, default: t.Any = None) -> t.Any:
+        """Look up a variable by name, or return a default if the key is
+        not found.
+
+        :param key: The variable name to look up.
+        :param default: The value to return if the key is not found.
+        """
+        try:
+            return self[key]
+        except KeyError:
+            return default
+
+    def resolve(self, key: str) -> t.Union[t.Any, "Undefined"]:
+        """Look up a variable by name, or return an :class:`Undefined`
+        object if the key is not found.
+
+        If you need to add custom behavior, override
+        :meth:`resolve_or_missing`, not this method. The various lookup
+        functions use that method, not this one.
+
+        :param key: The variable name to look up.
+        """
+        rv = self.resolve_or_missing(key)
+
+        if rv is missing:
+            return self.environment.undefined(name=key)
+
+        return rv
+
+    def resolve_or_missing(self, key: str) -> t.Any:
+        """Look up a variable by name, or return a ``missing`` sentinel
+        if the key is not found.
+
+        Override this method to add custom lookup behavior.
+        :meth:`resolve`, :meth:`get`, and :meth:`__getitem__` use this
+        method. Don't call this method directly.
+
+        :param key: The variable name to look up.
+        """
+        if key in self.vars:
+            return self.vars[key]
+
+        if key in self.parent:
+            return self.parent[key]
+
+        return missing
+
+    def get_exported(self) -> t.Dict[str, t.Any]:
+        """Get a new dict with the exported variables."""
+        return {k: self.vars[k] for k in self.exported_vars}
+
+    def get_all(self) -> t.Dict[str, t.Any]:
+        """Return the complete context as dict including the exported
+        variables.  For optimizations reasons this might not return an
+        actual copy so be careful with using it.
+        """
+        if not self.vars:
+            return self.parent
+        if not self.parent:
+            return self.vars
+        return dict(self.parent, **self.vars)
+
+    @internalcode
+    def call(
+        __self, __obj: t.Callable, *args: t.Any, **kwargs: t.Any  # noqa: B902
+    ) -> t.Union[t.Any, "Undefined"]:
+        """Call the callable with the arguments and keyword arguments
+        provided but inject the active context or environment as first
+        argument if the callable has :func:`pass_context` or
+        :func:`pass_environment`.
+        """
+        if __debug__:
+            __traceback_hide__ = True  # noqa
+
+        # Allow callable classes to take a context
+        if (
+            hasattr(__obj, "__call__")  # noqa: B004
+            and _PassArg.from_obj(__obj.__call__) is not None  # type: ignore
+        ):
+            __obj = __obj.__call__  # type: ignore
+
+        pass_arg = _PassArg.from_obj(__obj)
+
+        if pass_arg is _PassArg.context:
+            # the active context should have access to variables set in
+            # loops and blocks without mutating the context itself
+            if kwargs.get("_loop_vars"):
+                __self = __self.derived(kwargs["_loop_vars"])
+            if kwargs.get("_block_vars"):
+                __self = __self.derived(kwargs["_block_vars"])
+            args = (__self,) + args
+        elif pass_arg is _PassArg.eval_context:
+            args = (__self.eval_ctx,) + args
+        elif pass_arg is _PassArg.environment:
+            args = (__self.environment,) + args
+
+        kwargs.pop("_block_vars", None)
+        kwargs.pop("_loop_vars", None)
+
+        try:
+            return __obj(*args, **kwargs)
+        except StopIteration:
+            return __self.environment.undefined(
+                "value was undefined because a callable raised a"
+                " StopIteration exception"
+            )
+
+    def derived(self, locals: t.Optional[t.Dict[str, t.Any]] = None) -> "Context":
+        """Internal helper function to create a derived context.  This is
+        used in situations where the system needs a new context in the same
+        template that is independent.
+        """
+        context = new_context(
+            self.environment, self.name, {}, self.get_all(), True, None, locals
+        )
+        context.eval_ctx = self.eval_ctx
+        context.blocks.update((k, list(v)) for k, v in self.blocks.items())
+        return context
+
+    keys = _dict_method_all(dict.keys)
+    values = _dict_method_all(dict.values)
+    items = _dict_method_all(dict.items)
+
+    def __contains__(self, name: str) -> bool:
+        return name in self.vars or name in self.parent
+
+    def __getitem__(self, key: str) -> t.Any:
+        """Look up a variable by name with ``[]`` syntax, or raise a
+        ``KeyError`` if the key is not found.
+        """
+        item = self.resolve_or_missing(key)
+
+        if item is missing:
+            raise KeyError(key)
+
+        return item
+
+    def __repr__(self) -> str:
+        return f"<{type(self).__name__} {self.get_all()!r} of {self.name!r}>"
+
+
+class BlockReference:
+    """One block on a template reference."""
+
+    def __init__(
+        self,
+        name: str,
+        context: "Context",
+        stack: t.List[t.Callable[["Context"], t.Iterator[str]]],
+        depth: int,
+    ) -> None:
+        self.name = name
+        self._context = context
+        self._stack = stack
+        self._depth = depth
+
+    @property
+    def super(self) -> t.Union["BlockReference", "Undefined"]:
+        """Super the block."""
+        if self._depth + 1 >= len(self._stack):
+            return self._context.environment.undefined(
+                f"there is no parent block called {self.name!r}.", name="super"
+            )
+        return BlockReference(self.name, self._context, self._stack, self._depth + 1)
+
+    @internalcode
+    async def _async_call(self) -> str:
+        rv = concat(
+            [x async for x in self._stack[self._depth](self._context)]  # type: ignore
+        )
+
+        if self._context.eval_ctx.autoescape:
+            return Markup(rv)
+
+        return rv
+
+    @internalcode
+    def __call__(self) -> str:
+        if self._context.environment.is_async:
+            return self._async_call()  # type: ignore
+
+        rv = concat(self._stack[self._depth](self._context))
+
+        if self._context.eval_ctx.autoescape:
+            return Markup(rv)
+
+        return rv
+
+
+class LoopContext:
+    """A wrapper iterable for dynamic ``for`` loops, with information
+    about the loop and iteration.
+    """
+
+    #: Current iteration of the loop, starting at 0.
+    index0 = -1
+
+    _length: t.Optional[int] = None
+    _after: t.Any = missing
+    _current: t.Any = missing
+    _before: t.Any = missing
+    _last_changed_value: t.Any = missing
+
+    def __init__(
+        self,
+        iterable: t.Iterable[V],
+        undefined: t.Type["Undefined"],
+        recurse: t.Optional["LoopRenderFunc"] = None,
+        depth0: int = 0,
+    ) -> None:
+        """
+        :param iterable: Iterable to wrap.
+        :param undefined: :class:`Undefined` class to use for next and
+            previous items.
+        :param recurse: The function to render the loop body when the
+            loop is marked recursive.
+        :param depth0: Incremented when looping recursively.
+        """
+        self._iterable = iterable
+        self._iterator = self._to_iterator(iterable)
+        self._undefined = undefined
+        self._recurse = recurse
+        #: How many levels deep a recursive loop currently is, starting at 0.
+        self.depth0 = depth0
+
+    @staticmethod
+    def _to_iterator(iterable: t.Iterable[V]) -> t.Iterator[V]:
+        return iter(iterable)
+
+    @property
+    def length(self) -> int:
+        """Length of the iterable.
+
+        If the iterable is a generator or otherwise does not have a
+        size, it is eagerly evaluated to get a size.
+        """
+        if self._length is not None:
+            return self._length
+
+        try:
+            self._length = len(self._iterable)  # type: ignore
+        except TypeError:
+            iterable = list(self._iterator)
+            self._iterator = self._to_iterator(iterable)
+            self._length = len(iterable) + self.index + (self._after is not missing)
+
+        return self._length
+
+    def __len__(self) -> int:
+        return self.length
+
+    @property
+    def depth(self) -> int:
+        """How many levels deep a recursive loop currently is, starting at 1."""
+        return self.depth0 + 1
+
+    @property
+    def index(self) -> int:
+        """Current iteration of the loop, starting at 1."""
+        return self.index0 + 1
+
+    @property
+    def revindex0(self) -> int:
+        """Number of iterations from the end of the loop, ending at 0.
+
+        Requires calculating :attr:`length`.
+        """
+        return self.length - self.index
+
+    @property
+    def revindex(self) -> int:
+        """Number of iterations from the end of the loop, ending at 1.
+
+        Requires calculating :attr:`length`.
+        """
+        return self.length - self.index0
+
+    @property
+    def first(self) -> bool:
+        """Whether this is the first iteration of the loop."""
+        return self.index0 == 0
+
+    def _peek_next(self) -> t.Any:
+        """Return the next element in the iterable, or :data:`missing`
+        if the iterable is exhausted. Only peeks one item ahead, caching
+        the result in :attr:`_last` for use in subsequent checks. The
+        cache is reset when :meth:`__next__` is called.
+        """
+        if self._after is not missing:
+            return self._after
+
+        self._after = next(self._iterator, missing)
+        return self._after
+
+    @property
+    def last(self) -> bool:
+        """Whether this is the last iteration of the loop.
+
+        Causes the iterable to advance early. See
+        :func:`itertools.groupby` for issues this can cause.
+        The :func:`groupby` filter avoids that issue.
+        """
+        return self._peek_next() is missing
+
+    @property
+    def previtem(self) -> t.Union[t.Any, "Undefined"]:
+        """The item in the previous iteration. Undefined during the
+        first iteration.
+        """
+        if self.first:
+            return self._undefined("there is no previous item")
+
+        return self._before
+
+    @property
+    def nextitem(self) -> t.Union[t.Any, "Undefined"]:
+        """The item in the next iteration. Undefined during the last
+        iteration.
+
+        Causes the iterable to advance early. See
+        :func:`itertools.groupby` for issues this can cause.
+        The :func:`jinja-filters.groupby` filter avoids that issue.
+        """
+        rv = self._peek_next()
+
+        if rv is missing:
+            return self._undefined("there is no next item")
+
+        return rv
+
+    def cycle(self, *args: V) -> V:
+        """Return a value from the given args, cycling through based on
+        the current :attr:`index0`.
+
+        :param args: One or more values to cycle through.
+        """
+        if not args:
+            raise TypeError("no items for cycling given")
+
+        return args[self.index0 % len(args)]
+
+    def changed(self, *value: t.Any) -> bool:
+        """Return ``True`` if previously called with a different value
+        (including when called for the first time).
+
+        :param value: One or more values to compare to the last call.
+        """
+        if self._last_changed_value != value:
+            self._last_changed_value = value
+            return True
+
+        return False
+
+    def __iter__(self) -> "LoopContext":
+        return self
+
+    def __next__(self) -> t.Tuple[t.Any, "LoopContext"]:
+        if self._after is not missing:
+            rv = self._after
+            self._after = missing
+        else:
+            rv = next(self._iterator)
+
+        self.index0 += 1
+        self._before = self._current
+        self._current = rv
+        return rv, self
+
+    @internalcode
+    def __call__(self, iterable: t.Iterable[V]) -> str:
+        """When iterating over nested data, render the body of the loop
+        recursively with the given inner iterable data.
+
+        The loop must have the ``recursive`` marker for this to work.
+        """
+        if self._recurse is None:
+            raise TypeError(
+                "The loop must have the 'recursive' marker to be called recursively."
+            )
+
+        return self._recurse(iterable, self._recurse, depth=self.depth)
+
+    def __repr__(self) -> str:
+        return f"<{type(self).__name__} {self.index}/{self.length}>"
+
+
+class AsyncLoopContext(LoopContext):
+    _iterator: t.AsyncIterator[t.Any]  # type: ignore
+
+    @staticmethod
+    def _to_iterator(  # type: ignore
+        iterable: t.Union[t.Iterable[V], t.AsyncIterable[V]]
+    ) -> t.AsyncIterator[V]:
+        return auto_aiter(iterable)
+
+    @property
+    async def length(self) -> int:  # type: ignore
+        if self._length is not None:
+            return self._length
+
+        try:
+            self._length = len(self._iterable)  # type: ignore
+        except TypeError:
+            iterable = [x async for x in self._iterator]
+            self._iterator = self._to_iterator(iterable)
+            self._length = len(iterable) + self.index + (self._after is not missing)
+
+        return self._length
+
+    @property
+    async def revindex0(self) -> int:  # type: ignore
+        return await self.length - self.index
+
+    @property
+    async def revindex(self) -> int:  # type: ignore
+        return await self.length - self.index0
+
+    async def _peek_next(self) -> t.Any:
+        if self._after is not missing:
+            return self._after
+
+        try:
+            self._after = await self._iterator.__anext__()
+        except StopAsyncIteration:
+            self._after = missing
+
+        return self._after
+
+    @property
+    async def last(self) -> bool:  # type: ignore
+        return await self._peek_next() is missing
+
+    @property
+    async def nextitem(self) -> t.Union[t.Any, "Undefined"]:
+        rv = await self._peek_next()
+
+        if rv is missing:
+            return self._undefined("there is no next item")
+
+        return rv
+
+    def __aiter__(self) -> "AsyncLoopContext":
+        return self
+
+    async def __anext__(self) -> t.Tuple[t.Any, "AsyncLoopContext"]:
+        if self._after is not missing:
+            rv = self._after
+            self._after = missing
+        else:
+            rv = await self._iterator.__anext__()
+
+        self.index0 += 1
+        self._before = self._current
+        self._current = rv
+        return rv, self
+
+
+class Macro:
+    """Wraps a macro function."""
+
+    def __init__(
+        self,
+        environment: "Environment",
+        func: t.Callable[..., str],
+        name: str,
+        arguments: t.List[str],
+        catch_kwargs: bool,
+        catch_varargs: bool,
+        caller: bool,
+        default_autoescape: t.Optional[bool] = None,
+    ):
+        self._environment = environment
+        self._func = func
+        self._argument_count = len(arguments)
+        self.name = name
+        self.arguments = arguments
+        self.catch_kwargs = catch_kwargs
+        self.catch_varargs = catch_varargs
+        self.caller = caller
+        self.explicit_caller = "caller" in arguments
+
+        if default_autoescape is None:
+            if callable(environment.autoescape):
+                default_autoescape = environment.autoescape(None)
+            else:
+                default_autoescape = environment.autoescape
+
+        self._default_autoescape = default_autoescape
+
+    @internalcode
+    @pass_eval_context
+    def __call__(self, *args: t.Any, **kwargs: t.Any) -> str:
+        # This requires a bit of explanation,  In the past we used to
+        # decide largely based on compile-time information if a macro is
+        # safe or unsafe.  While there was a volatile mode it was largely
+        # unused for deciding on escaping.  This turns out to be
+        # problematic for macros because whether a macro is safe depends not
+        # on the escape mode when it was defined, but rather when it was used.
+        #
+        # Because however we export macros from the module system and
+        # there are historic callers that do not pass an eval context (and
+        # will continue to not pass one), we need to perform an instance
+        # check here.
+        #
+        # This is considered safe because an eval context is not a valid
+        # argument to callables otherwise anyway.  Worst case here is
+        # that if no eval context is passed we fall back to the compile
+        # time autoescape flag.
+        if args and isinstance(args[0], EvalContext):
+            autoescape = args[0].autoescape
+            args = args[1:]
+        else:
+            autoescape = self._default_autoescape
+
+        # try to consume the positional arguments
+        arguments = list(args[: self._argument_count])
+        off = len(arguments)
+
+        # For information why this is necessary refer to the handling
+        # of caller in the `macro_body` handler in the compiler.
+        found_caller = False
+
+        # if the number of arguments consumed is not the number of
+        # arguments expected we start filling in keyword arguments
+        # and defaults.
+        if off != self._argument_count:
+            for name in self.arguments[len(arguments) :]:
+                try:
+                    value = kwargs.pop(name)
+                except KeyError:
+                    value = missing
+                if name == "caller":
+                    found_caller = True
+                arguments.append(value)
+        else:
+            found_caller = self.explicit_caller
+
+        # it's important that the order of these arguments does not change
+        # if not also changed in the compiler's `function_scoping` method.
+        # the order is caller, keyword arguments, positional arguments!
+        if self.caller and not found_caller:
+            caller = kwargs.pop("caller", None)
+            if caller is None:
+                caller = self._environment.undefined("No caller defined", name="caller")
+            arguments.append(caller)
+
+        if self.catch_kwargs:
+            arguments.append(kwargs)
+        elif kwargs:
+            if "caller" in kwargs:
+                raise TypeError(
+                    f"macro {self.name!r} was invoked with two values for the special"
+                    " caller argument. This is most likely a bug."
+                )
+            raise TypeError(
+                f"macro {self.name!r} takes no keyword argument {next(iter(kwargs))!r}"
+            )
+        if self.catch_varargs:
+            arguments.append(args[self._argument_count :])
+        elif len(args) > self._argument_count:
+            raise TypeError(
+                f"macro {self.name!r} takes not more than"
+                f" {len(self.arguments)} argument(s)"
+            )
+
+        return self._invoke(arguments, autoescape)
+
+    async def _async_invoke(self, arguments: t.List[t.Any], autoescape: bool) -> str:
+        rv = await self._func(*arguments)  # type: ignore
+
+        if autoescape:
+            return Markup(rv)
+
+        return rv  # type: ignore
+
+    def _invoke(self, arguments: t.List[t.Any], autoescape: bool) -> str:
+        if self._environment.is_async:
+            return self._async_invoke(arguments, autoescape)  # type: ignore
+
+        rv = self._func(*arguments)
+
+        if autoescape:
+            rv = Markup(rv)
+
+        return rv
+
+    def __repr__(self) -> str:
+        name = "anonymous" if self.name is None else repr(self.name)
+        return f"<{type(self).__name__} {name}>"
+
+
+class Undefined:
+    """The default undefined type.  This undefined type can be printed and
+    iterated over, but every other access will raise an :exc:`UndefinedError`:
+
+    >>> foo = Undefined(name='foo')
+    >>> str(foo)
+    ''
+    >>> not foo
+    True
+    >>> foo + 42
+    Traceback (most recent call last):
+      ...
+    jinja2.exceptions.UndefinedError: 'foo' is undefined
+    """
+
+    __slots__ = (
+        "_undefined_hint",
+        "_undefined_obj",
+        "_undefined_name",
+        "_undefined_exception",
+    )
+
+    def __init__(
+        self,
+        hint: t.Optional[str] = None,
+        obj: t.Any = missing,
+        name: t.Optional[str] = None,
+        exc: t.Type[TemplateRuntimeError] = UndefinedError,
+    ) -> None:
+        self._undefined_hint = hint
+        self._undefined_obj = obj
+        self._undefined_name = name
+        self._undefined_exception = exc
+
+    @property
+    def _undefined_message(self) -> str:
+        """Build a message about the undefined value based on how it was
+        accessed.
+        """
+        if self._undefined_hint:
+            return self._undefined_hint
+
+        if self._undefined_obj is missing:
+            return f"{self._undefined_name!r} is undefined"
+
+        if not isinstance(self._undefined_name, str):
+            return (
+                f"{object_type_repr(self._undefined_obj)} has no"
+                f" element {self._undefined_name!r}"
+            )
+
+        return (
+            f"{object_type_repr(self._undefined_obj)!r} has no"
+            f" attribute {self._undefined_name!r}"
+        )
+
+    @internalcode
+    def _fail_with_undefined_error(
+        self, *args: t.Any, **kwargs: t.Any
+    ) -> "te.NoReturn":
+        """Raise an :exc:`UndefinedError` when operations are performed
+        on the undefined value.
+        """
+        raise self._undefined_exception(self._undefined_message)
+
+    @internalcode
+    def __getattr__(self, name: str) -> t.Any:
+        if name[:2] == "__":
+            raise AttributeError(name)
+
+        return self._fail_with_undefined_error()
+
+    __add__ = __radd__ = __sub__ = __rsub__ = _fail_with_undefined_error
+    __mul__ = __rmul__ = __div__ = __rdiv__ = _fail_with_undefined_error
+    __truediv__ = __rtruediv__ = _fail_with_undefined_error
+    __floordiv__ = __rfloordiv__ = _fail_with_undefined_error
+    __mod__ = __rmod__ = _fail_with_undefined_error
+    __pos__ = __neg__ = _fail_with_undefined_error
+    __call__ = __getitem__ = _fail_with_undefined_error
+    __lt__ = __le__ = __gt__ = __ge__ = _fail_with_undefined_error
+    __int__ = __float__ = __complex__ = _fail_with_undefined_error
+    __pow__ = __rpow__ = _fail_with_undefined_error
+
+    def __eq__(self, other: t.Any) -> bool:
+        return type(self) is type(other)
+
+    def __ne__(self, other: t.Any) -> bool:
+        return not self.__eq__(other)
+
+    def __hash__(self) -> int:
+        return id(type(self))
+
+    def __str__(self) -> str:
+        return ""
+
+    def __len__(self) -> int:
+        return 0
+
+    def __iter__(self) -> t.Iterator[t.Any]:
+        yield from ()
+
+    async def __aiter__(self) -> t.AsyncIterator[t.Any]:
+        for _ in ():
+            yield
+
+    def __bool__(self) -> bool:
+        return False
+
+    def __repr__(self) -> str:
+        return "Undefined"
+
+
+def make_logging_undefined(
+    logger: t.Optional["logging.Logger"] = None, base: t.Type[Undefined] = Undefined
+) -> t.Type[Undefined]:
+    """Given a logger object this returns a new undefined class that will
+    log certain failures.  It will log iterations and printing.  If no
+    logger is given a default logger is created.
+
+    Example::
+
+        logger = logging.getLogger(__name__)
+        LoggingUndefined = make_logging_undefined(
+            logger=logger,
+            base=Undefined
+        )
+
+    .. versionadded:: 2.8
+
+    :param logger: the logger to use.  If not provided, a default logger
+                   is created.
+    :param base: the base class to add logging functionality to.  This
+                 defaults to :class:`Undefined`.
+    """
+    if logger is None:
+        import logging
+
+        logger = logging.getLogger(__name__)
+        logger.addHandler(logging.StreamHandler(sys.stderr))
+
+    def _log_message(undef: Undefined) -> None:
+        logger.warning(  # type: ignore
+            "Template variable warning: %s", undef._undefined_message
+        )
+
+    class LoggingUndefined(base):  # type: ignore
+        __slots__ = ()
+
+        def _fail_with_undefined_error(  # type: ignore
+            self, *args: t.Any, **kwargs: t.Any
+        ) -> "te.NoReturn":
+            try:
+                super()._fail_with_undefined_error(*args, **kwargs)
+            except self._undefined_exception as e:
+                logger.error("Template variable error: %s", e)  # type: ignore
+                raise e
+
+        def __str__(self) -> str:
+            _log_message(self)
+            return super().__str__()  # type: ignore
+
+        def __iter__(self) -> t.Iterator[t.Any]:
+            _log_message(self)
+            return super().__iter__()  # type: ignore
+
+        def __bool__(self) -> bool:
+            _log_message(self)
+            return super().__bool__()  # type: ignore
+
+    return LoggingUndefined
+
+
+class ChainableUndefined(Undefined):
+    """An undefined that is chainable, where both ``__getattr__`` and
+    ``__getitem__`` return itself rather than raising an
+    :exc:`UndefinedError`.
+
+    >>> foo = ChainableUndefined(name='foo')
+    >>> str(foo.bar['baz'])
+    ''
+    >>> foo.bar['baz'] + 42
+    Traceback (most recent call last):
+      ...
+    jinja2.exceptions.UndefinedError: 'foo' is undefined
+
+    .. versionadded:: 2.11.0
+    """
+
+    __slots__ = ()
+
+    def __html__(self) -> str:
+        return str(self)
+
+    def __getattr__(self, _: str) -> "ChainableUndefined":
+        return self
+
+    __getitem__ = __getattr__  # type: ignore
+
+
+class DebugUndefined(Undefined):
+    """An undefined that returns the debug info when printed.
+
+    >>> foo = DebugUndefined(name='foo')
+    >>> str(foo)
+    '{{ foo }}'
+    >>> not foo
+    True
+    >>> foo + 42
+    Traceback (most recent call last):
+      ...
+    jinja2.exceptions.UndefinedError: 'foo' is undefined
+    """
+
+    __slots__ = ()
+
+    def __str__(self) -> str:
+        if self._undefined_hint:
+            message = f"undefined value printed: {self._undefined_hint}"
+
+        elif self._undefined_obj is missing:
+            message = self._undefined_name  # type: ignore
+
+        else:
+            message = (
+                f"no such element: {object_type_repr(self._undefined_obj)}"
+                f"[{self._undefined_name!r}]"
+            )
+
+        return f"{{{{ {message} }}}}"
+
+
+class StrictUndefined(Undefined):
+    """An undefined that barks on print and iteration as well as boolean
+    tests and all kinds of comparisons.  In other words: you can do nothing
+    with it except checking if it's defined using the `defined` test.
+
+    >>> foo = StrictUndefined(name='foo')
+    >>> str(foo)
+    Traceback (most recent call last):
+      ...
+    jinja2.exceptions.UndefinedError: 'foo' is undefined
+    >>> not foo
+    Traceback (most recent call last):
+      ...
+    jinja2.exceptions.UndefinedError: 'foo' is undefined
+    >>> foo + 42
+    Traceback (most recent call last):
+      ...
+    jinja2.exceptions.UndefinedError: 'foo' is undefined
+    """
+
+    __slots__ = ()
+    __iter__ = __str__ = __len__ = Undefined._fail_with_undefined_error
+    __eq__ = __ne__ = __bool__ = __hash__ = Undefined._fail_with_undefined_error
+    __contains__ = Undefined._fail_with_undefined_error
+
+
+# Remove slots attributes, after the metaclass is applied they are
+# unneeded and contain wrong data for subclasses.
+del (
+    Undefined.__slots__,
+    ChainableUndefined.__slots__,
+    DebugUndefined.__slots__,
+    StrictUndefined.__slots__,
+)