mirror of https://github.com/python/cpython
728 lines
26 KiB
Python
728 lines
26 KiB
Python
"""Helpers for introspecting and wrapping annotations."""
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import ast
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import enum
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import functools
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import sys
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import types
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__all__ = [
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"Format",
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"ForwardRef",
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"call_annotate_function",
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"call_evaluate_function",
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"get_annotate_function",
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"get_annotations",
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]
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class Format(enum.IntEnum):
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VALUE = 1
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FORWARDREF = 2
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SOURCE = 3
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_Union = None
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_sentinel = object()
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# Slots shared by ForwardRef and _Stringifier. The __forward__ names must be
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# preserved for compatibility with the old typing.ForwardRef class. The remaining
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# names are private.
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_SLOTS = (
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"__forward_evaluated__",
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"__forward_value__",
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"__forward_is_argument__",
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"__forward_is_class__",
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"__forward_module__",
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"__weakref__",
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"__arg__",
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"__ast_node__",
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"__code__",
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"__globals__",
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"__owner__",
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"__cell__",
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)
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class ForwardRef:
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"""Wrapper that holds a forward reference.
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Constructor arguments:
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* arg: a string representing the code to be evaluated.
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* module: the module where the forward reference was created.
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Must be a string, not a module object.
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* owner: The owning object (module, class, or function).
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* is_argument: Does nothing, retained for compatibility.
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* is_class: True if the forward reference was created in class scope.
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"""
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__slots__ = _SLOTS
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def __init__(
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self,
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arg,
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*,
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module=None,
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owner=None,
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is_argument=True,
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is_class=False,
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):
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if not isinstance(arg, str):
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raise TypeError(f"Forward reference must be a string -- got {arg!r}")
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self.__arg__ = arg
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self.__forward_evaluated__ = False
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self.__forward_value__ = None
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self.__forward_is_argument__ = is_argument
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self.__forward_is_class__ = is_class
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self.__forward_module__ = module
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self.__code__ = None
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self.__ast_node__ = None
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self.__globals__ = None
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self.__cell__ = None
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self.__owner__ = owner
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def __init_subclass__(cls, /, *args, **kwds):
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raise TypeError("Cannot subclass ForwardRef")
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def evaluate(self, *, globals=None, locals=None, type_params=None, owner=None):
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"""Evaluate the forward reference and return the value.
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If the forward reference cannot be evaluated, raise an exception.
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"""
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if self.__forward_evaluated__:
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return self.__forward_value__
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if self.__cell__ is not None:
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try:
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value = self.__cell__.cell_contents
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except ValueError:
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pass
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else:
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self.__forward_evaluated__ = True
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self.__forward_value__ = value
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return value
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if owner is None:
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owner = self.__owner__
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if globals is None and self.__forward_module__ is not None:
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globals = getattr(
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sys.modules.get(self.__forward_module__, None), "__dict__", None
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)
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if globals is None:
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globals = self.__globals__
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if globals is None:
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if isinstance(owner, type):
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module_name = getattr(owner, "__module__", None)
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if module_name:
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module = sys.modules.get(module_name, None)
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if module:
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globals = getattr(module, "__dict__", None)
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elif isinstance(owner, types.ModuleType):
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globals = getattr(owner, "__dict__", None)
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elif callable(owner):
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globals = getattr(owner, "__globals__", None)
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# If we pass None to eval() below, the globals of this module are used.
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if globals is None:
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globals = {}
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if locals is None:
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locals = {}
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if isinstance(owner, type):
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locals.update(vars(owner))
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if type_params is None and owner is not None:
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# "Inject" type parameters into the local namespace
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# (unless they are shadowed by assignments *in* the local namespace),
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# as a way of emulating annotation scopes when calling `eval()`
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type_params = getattr(owner, "__type_params__", None)
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# type parameters require some special handling,
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# as they exist in their own scope
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# but `eval()` does not have a dedicated parameter for that scope.
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# For classes, names in type parameter scopes should override
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# names in the global scope (which here are called `localns`!),
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# but should in turn be overridden by names in the class scope
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# (which here are called `globalns`!)
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if type_params is not None:
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globals = dict(globals)
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locals = dict(locals)
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for param in type_params:
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param_name = param.__name__
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if not self.__forward_is_class__ or param_name not in globals:
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globals[param_name] = param
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locals.pop(param_name, None)
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code = self.__forward_code__
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value = eval(code, globals=globals, locals=locals)
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self.__forward_evaluated__ = True
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self.__forward_value__ = value
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return value
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def _evaluate(self, globalns, localns, type_params=_sentinel, *, recursive_guard):
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import typing
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import warnings
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if type_params is _sentinel:
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typing._deprecation_warning_for_no_type_params_passed(
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"typing.ForwardRef._evaluate"
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)
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type_params = ()
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warnings._deprecated(
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"ForwardRef._evaluate",
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"{name} is a private API and is retained for compatibility, but will be removed"
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" in Python 3.16. Use ForwardRef.evaluate() or typing.evaluate_forward_ref() instead.",
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remove=(3, 16),
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)
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return typing.evaluate_forward_ref(
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self,
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globals=globalns,
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locals=localns,
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type_params=type_params,
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_recursive_guard=recursive_guard,
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)
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@property
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def __forward_arg__(self):
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if self.__arg__ is not None:
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return self.__arg__
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if self.__ast_node__ is not None:
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self.__arg__ = ast.unparse(self.__ast_node__)
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return self.__arg__
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raise AssertionError(
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"Attempted to access '__forward_arg__' on an uninitialized ForwardRef"
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)
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@property
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def __forward_code__(self):
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if self.__code__ is not None:
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return self.__code__
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arg = self.__forward_arg__
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# If we do `def f(*args: *Ts)`, then we'll have `arg = '*Ts'`.
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# Unfortunately, this isn't a valid expression on its own, so we
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# do the unpacking manually.
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if arg.startswith("*"):
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arg_to_compile = f"({arg},)[0]" # E.g. (*Ts,)[0] or (*tuple[int, int],)[0]
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else:
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arg_to_compile = arg
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try:
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self.__code__ = compile(arg_to_compile, "<string>", "eval")
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except SyntaxError:
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raise SyntaxError(f"Forward reference must be an expression -- got {arg!r}")
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return self.__code__
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def __eq__(self, other):
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if not isinstance(other, ForwardRef):
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return NotImplemented
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if self.__forward_evaluated__ and other.__forward_evaluated__:
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return (
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self.__forward_arg__ == other.__forward_arg__
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and self.__forward_value__ == other.__forward_value__
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)
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return (
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self.__forward_arg__ == other.__forward_arg__
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and self.__forward_module__ == other.__forward_module__
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)
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def __hash__(self):
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return hash((self.__forward_arg__, self.__forward_module__))
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def __or__(self, other):
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global _Union
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if _Union is None:
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from typing import Union as _Union
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return _Union[self, other]
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def __ror__(self, other):
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global _Union
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if _Union is None:
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from typing import Union as _Union
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return _Union[other, self]
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def __repr__(self):
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if self.__forward_module__ is None:
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module_repr = ""
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else:
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module_repr = f", module={self.__forward_module__!r}"
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return f"ForwardRef({self.__forward_arg__!r}{module_repr})"
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class _Stringifier:
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# Must match the slots on ForwardRef, so we can turn an instance of one into an
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# instance of the other in place.
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__slots__ = _SLOTS
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def __init__(self, node, globals=None, owner=None, is_class=False, cell=None):
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assert isinstance(node, ast.AST)
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self.__arg__ = None
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self.__forward_evaluated__ = False
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self.__forward_value__ = None
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self.__forward_is_argument__ = False
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self.__forward_is_class__ = is_class
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self.__forward_module__ = None
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self.__code__ = None
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self.__ast_node__ = node
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self.__globals__ = globals
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self.__cell__ = cell
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self.__owner__ = owner
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def __convert(self, other):
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if isinstance(other, _Stringifier):
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return other.__ast_node__
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elif isinstance(other, slice):
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return ast.Slice(
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lower=self.__convert(other.start) if other.start is not None else None,
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upper=self.__convert(other.stop) if other.stop is not None else None,
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step=self.__convert(other.step) if other.step is not None else None,
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)
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else:
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return ast.Constant(value=other)
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def __make_new(self, node):
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return _Stringifier(
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node, self.__globals__, self.__owner__, self.__forward_is_class__
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)
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# Must implement this since we set __eq__. We hash by identity so that
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# stringifiers in dict keys are kept separate.
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def __hash__(self):
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return id(self)
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def __getitem__(self, other):
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# Special case, to avoid stringifying references to class-scoped variables
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# as '__classdict__["x"]'.
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if (
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isinstance(self.__ast_node__, ast.Name)
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and self.__ast_node__.id == "__classdict__"
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):
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raise KeyError
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if isinstance(other, tuple):
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elts = [self.__convert(elt) for elt in other]
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other = ast.Tuple(elts)
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else:
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other = self.__convert(other)
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assert isinstance(other, ast.AST), repr(other)
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return self.__make_new(ast.Subscript(self.__ast_node__, other))
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def __getattr__(self, attr):
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return self.__make_new(ast.Attribute(self.__ast_node__, attr))
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def __call__(self, *args, **kwargs):
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return self.__make_new(
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ast.Call(
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self.__ast_node__,
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[self.__convert(arg) for arg in args],
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[
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ast.keyword(key, self.__convert(value))
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for key, value in kwargs.items()
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],
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)
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)
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def __iter__(self):
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yield self.__make_new(ast.Starred(self.__ast_node__))
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def __repr__(self):
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return ast.unparse(self.__ast_node__)
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def __format__(self, format_spec):
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raise TypeError("Cannot stringify annotation containing string formatting")
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def _make_binop(op: ast.AST):
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def binop(self, other):
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return self.__make_new(
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ast.BinOp(self.__ast_node__, op, self.__convert(other))
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)
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return binop
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__add__ = _make_binop(ast.Add())
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__sub__ = _make_binop(ast.Sub())
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__mul__ = _make_binop(ast.Mult())
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__matmul__ = _make_binop(ast.MatMult())
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__truediv__ = _make_binop(ast.Div())
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__mod__ = _make_binop(ast.Mod())
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__lshift__ = _make_binop(ast.LShift())
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__rshift__ = _make_binop(ast.RShift())
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__or__ = _make_binop(ast.BitOr())
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__xor__ = _make_binop(ast.BitXor())
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__and__ = _make_binop(ast.BitAnd())
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__floordiv__ = _make_binop(ast.FloorDiv())
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__pow__ = _make_binop(ast.Pow())
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del _make_binop
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def _make_rbinop(op: ast.AST):
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def rbinop(self, other):
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return self.__make_new(
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ast.BinOp(self.__convert(other), op, self.__ast_node__)
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)
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return rbinop
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__radd__ = _make_rbinop(ast.Add())
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__rsub__ = _make_rbinop(ast.Sub())
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__rmul__ = _make_rbinop(ast.Mult())
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__rmatmul__ = _make_rbinop(ast.MatMult())
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__rtruediv__ = _make_rbinop(ast.Div())
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__rmod__ = _make_rbinop(ast.Mod())
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__rlshift__ = _make_rbinop(ast.LShift())
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__rrshift__ = _make_rbinop(ast.RShift())
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__ror__ = _make_rbinop(ast.BitOr())
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__rxor__ = _make_rbinop(ast.BitXor())
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__rand__ = _make_rbinop(ast.BitAnd())
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__rfloordiv__ = _make_rbinop(ast.FloorDiv())
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__rpow__ = _make_rbinop(ast.Pow())
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del _make_rbinop
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def _make_compare(op):
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def compare(self, other):
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return self.__make_new(
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ast.Compare(
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left=self.__ast_node__,
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ops=[op],
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comparators=[self.__convert(other)],
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)
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)
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return compare
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__lt__ = _make_compare(ast.Lt())
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__le__ = _make_compare(ast.LtE())
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__eq__ = _make_compare(ast.Eq())
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__ne__ = _make_compare(ast.NotEq())
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__gt__ = _make_compare(ast.Gt())
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__ge__ = _make_compare(ast.GtE())
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del _make_compare
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def _make_unary_op(op):
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def unary_op(self):
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return self.__make_new(ast.UnaryOp(op, self.__ast_node__))
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return unary_op
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__invert__ = _make_unary_op(ast.Invert())
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__pos__ = _make_unary_op(ast.UAdd())
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__neg__ = _make_unary_op(ast.USub())
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del _make_unary_op
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class _StringifierDict(dict):
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def __init__(self, namespace, globals=None, owner=None, is_class=False):
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super().__init__(namespace)
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self.namespace = namespace
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self.globals = globals
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self.owner = owner
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self.is_class = is_class
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self.stringifiers = []
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def __missing__(self, key):
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fwdref = _Stringifier(
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ast.Name(id=key),
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globals=self.globals,
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owner=self.owner,
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is_class=self.is_class,
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)
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self.stringifiers.append(fwdref)
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return fwdref
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def call_evaluate_function(evaluate, format, *, owner=None):
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"""Call an evaluate function. Evaluate functions are normally generated for
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the value of type aliases and the bounds, constraints, and defaults of
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type parameter objects.
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"""
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return call_annotate_function(evaluate, format, owner=owner, _is_evaluate=True)
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def call_annotate_function(annotate, format, *, owner=None, _is_evaluate=False):
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"""Call an __annotate__ function. __annotate__ functions are normally
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generated by the compiler to defer the evaluation of annotations. They
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can be called with any of the format arguments in the Format enum, but
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compiler-generated __annotate__ functions only support the VALUE format.
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This function provides additional functionality to call __annotate__
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functions with the FORWARDREF and SOURCE formats.
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*annotate* must be an __annotate__ function, which takes a single argument
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and returns a dict of annotations.
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*format* must be a member of the Format enum or one of the corresponding
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integer values.
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*owner* can be the object that owns the annotations (i.e., the module,
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class, or function that the __annotate__ function derives from). With the
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FORWARDREF format, it is used to provide better evaluation capabilities
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on the generated ForwardRef objects.
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"""
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try:
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return annotate(format)
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except NotImplementedError:
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pass
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if format == Format.SOURCE:
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# SOURCE is implemented by calling the annotate function in a special
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# environment where every name lookup results in an instance of _Stringifier.
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# _Stringifier supports every dunder operation and returns a new _Stringifier.
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# At the end, we get a dictionary that mostly contains _Stringifier objects (or
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# possibly constants if the annotate function uses them directly). We then
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# convert each of those into a string to get an approximation of the
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# original source.
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globals = _StringifierDict({})
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if annotate.__closure__:
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freevars = annotate.__code__.co_freevars
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new_closure = []
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for i, cell in enumerate(annotate.__closure__):
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if i < len(freevars):
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name = freevars[i]
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else:
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name = "__cell__"
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fwdref = _Stringifier(ast.Name(id=name))
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new_closure.append(types.CellType(fwdref))
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closure = tuple(new_closure)
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else:
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closure = None
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func = types.FunctionType(
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annotate.__code__,
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globals,
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closure=closure,
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argdefs=annotate.__defaults__,
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kwdefaults=annotate.__kwdefaults__,
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)
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annos = func(Format.VALUE)
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if _is_evaluate:
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return annos if isinstance(annos, str) else repr(annos)
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return {
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key: val if isinstance(val, str) else repr(val)
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for key, val in annos.items()
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}
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elif format == Format.FORWARDREF:
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# FORWARDREF is implemented similarly to SOURCE, but there are two changes,
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# at the beginning and the end of the process.
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# First, while SOURCE uses an empty dictionary as the namespace, so that all
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# name lookups result in _Stringifier objects, FORWARDREF uses the globals
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# and builtins, so that defined names map to their real values.
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# Second, instead of returning strings, we want to return either real values
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# or ForwardRef objects. To do this, we keep track of all _Stringifier objects
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# created while the annotation is being evaluated, and at the end we convert
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# them all to ForwardRef objects by assigning to __class__. To make this
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# technique work, we have to ensure that the _Stringifier and ForwardRef
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# classes share the same attributes.
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# We use this technique because while the annotations are being evaluated,
|
|
# we want to support all operations that the language allows, including even
|
|
# __getattr__ and __eq__, and return new _Stringifier objects so we can accurately
|
|
# reconstruct the source. But in the dictionary that we eventually return, we
|
|
# want to return objects with more user-friendly behavior, such as an __eq__
|
|
# that returns a bool and an defined set of attributes.
|
|
namespace = {**annotate.__builtins__, **annotate.__globals__}
|
|
is_class = isinstance(owner, type)
|
|
globals = _StringifierDict(namespace, annotate.__globals__, owner, is_class)
|
|
if annotate.__closure__:
|
|
freevars = annotate.__code__.co_freevars
|
|
new_closure = []
|
|
for i, cell in enumerate(annotate.__closure__):
|
|
try:
|
|
cell.cell_contents
|
|
except ValueError:
|
|
if i < len(freevars):
|
|
name = freevars[i]
|
|
else:
|
|
name = "__cell__"
|
|
fwdref = _Stringifier(
|
|
ast.Name(id=name),
|
|
cell=cell,
|
|
owner=owner,
|
|
globals=annotate.__globals__,
|
|
is_class=is_class,
|
|
)
|
|
globals.stringifiers.append(fwdref)
|
|
new_closure.append(types.CellType(fwdref))
|
|
else:
|
|
new_closure.append(cell)
|
|
closure = tuple(new_closure)
|
|
else:
|
|
closure = None
|
|
func = types.FunctionType(
|
|
annotate.__code__,
|
|
globals,
|
|
closure=closure,
|
|
argdefs=annotate.__defaults__,
|
|
kwdefaults=annotate.__kwdefaults__,
|
|
)
|
|
result = func(Format.VALUE)
|
|
for obj in globals.stringifiers:
|
|
obj.__class__ = ForwardRef
|
|
return result
|
|
elif format == Format.VALUE:
|
|
# Should be impossible because __annotate__ functions must not raise
|
|
# NotImplementedError for this format.
|
|
raise RuntimeError("annotate function does not support VALUE format")
|
|
else:
|
|
raise ValueError(f"Invalid format: {format!r}")
|
|
|
|
|
|
# We use the descriptors from builtins.type instead of accessing
|
|
# .__annotations__ and .__annotate__ directly on class objects, because
|
|
# otherwise we could get wrong results in some cases involving metaclasses.
|
|
# See PEP 749.
|
|
_BASE_GET_ANNOTATE = type.__dict__["__annotate__"].__get__
|
|
_BASE_GET_ANNOTATIONS = type.__dict__["__annotations__"].__get__
|
|
|
|
|
|
def get_annotate_function(obj):
|
|
"""Get the __annotate__ function for an object.
|
|
|
|
obj may be a function, class, or module, or a user-defined type with
|
|
an `__annotate__` attribute.
|
|
|
|
Returns the __annotate__ function or None.
|
|
"""
|
|
if isinstance(obj, type):
|
|
try:
|
|
return _BASE_GET_ANNOTATE(obj)
|
|
except AttributeError:
|
|
# AttributeError is raised for static types.
|
|
return None
|
|
return getattr(obj, "__annotate__", None)
|
|
|
|
|
|
def get_annotations(
|
|
obj, *, globals=None, locals=None, eval_str=False, format=Format.VALUE
|
|
):
|
|
"""Compute the annotations dict for an object.
|
|
|
|
obj may be a callable, class, or module.
|
|
Passing in an object of any other type raises TypeError.
|
|
|
|
Returns a dict. get_annotations() returns a new dict every time
|
|
it's called; calling it twice on the same object will return two
|
|
different but equivalent dicts.
|
|
|
|
This function handles several details for you:
|
|
|
|
* If eval_str is true, values of type str will
|
|
be un-stringized using eval(). This is intended
|
|
for use with stringized annotations
|
|
("from __future__ import annotations").
|
|
* If obj doesn't have an annotations dict, returns an
|
|
empty dict. (Functions and methods always have an
|
|
annotations dict; classes, modules, and other types of
|
|
callables may not.)
|
|
* Ignores inherited annotations on classes. If a class
|
|
doesn't have its own annotations dict, returns an empty dict.
|
|
* All accesses to object members and dict values are done
|
|
using getattr() and dict.get() for safety.
|
|
* Always, always, always returns a freshly-created dict.
|
|
|
|
eval_str controls whether or not values of type str are replaced
|
|
with the result of calling eval() on those values:
|
|
|
|
* If eval_str is true, eval() is called on values of type str.
|
|
* If eval_str is false (the default), values of type str are unchanged.
|
|
|
|
globals and locals are passed in to eval(); see the documentation
|
|
for eval() for more information. If either globals or locals is
|
|
None, this function may replace that value with a context-specific
|
|
default, contingent on type(obj):
|
|
|
|
* If obj is a module, globals defaults to obj.__dict__.
|
|
* If obj is a class, globals defaults to
|
|
sys.modules[obj.__module__].__dict__ and locals
|
|
defaults to the obj class namespace.
|
|
* If obj is a callable, globals defaults to obj.__globals__,
|
|
although if obj is a wrapped function (using
|
|
functools.update_wrapper()) it is first unwrapped.
|
|
"""
|
|
if eval_str and format != Format.VALUE:
|
|
raise ValueError("eval_str=True is only supported with format=Format.VALUE")
|
|
|
|
# For VALUE format, we look at __annotations__ directly.
|
|
if format != Format.VALUE:
|
|
annotate = get_annotate_function(obj)
|
|
if annotate is not None:
|
|
ann = call_annotate_function(annotate, format, owner=obj)
|
|
if not isinstance(ann, dict):
|
|
raise ValueError(f"{obj!r}.__annotate__ returned a non-dict")
|
|
return dict(ann)
|
|
|
|
if isinstance(obj, type):
|
|
try:
|
|
ann = _BASE_GET_ANNOTATIONS(obj)
|
|
except AttributeError:
|
|
# For static types, the descriptor raises AttributeError.
|
|
return {}
|
|
else:
|
|
ann = getattr(obj, "__annotations__", None)
|
|
if ann is None:
|
|
return {}
|
|
|
|
if not isinstance(ann, dict):
|
|
raise ValueError(f"{obj!r}.__annotations__ is neither a dict nor None")
|
|
|
|
if not ann:
|
|
return {}
|
|
|
|
if not eval_str:
|
|
return dict(ann)
|
|
|
|
if isinstance(obj, type):
|
|
# class
|
|
obj_globals = None
|
|
module_name = getattr(obj, "__module__", None)
|
|
if module_name:
|
|
module = sys.modules.get(module_name, None)
|
|
if module:
|
|
obj_globals = getattr(module, "__dict__", None)
|
|
obj_locals = dict(vars(obj))
|
|
unwrap = obj
|
|
elif isinstance(obj, types.ModuleType):
|
|
# module
|
|
obj_globals = getattr(obj, "__dict__")
|
|
obj_locals = None
|
|
unwrap = None
|
|
elif callable(obj):
|
|
# this includes types.Function, types.BuiltinFunctionType,
|
|
# types.BuiltinMethodType, functools.partial, functools.singledispatch,
|
|
# "class funclike" from Lib/test/test_inspect... on and on it goes.
|
|
obj_globals = getattr(obj, "__globals__", None)
|
|
obj_locals = None
|
|
unwrap = obj
|
|
elif ann is not None:
|
|
obj_globals = obj_locals = unwrap = None
|
|
else:
|
|
raise TypeError(f"{obj!r} is not a module, class, or callable.")
|
|
|
|
if unwrap is not None:
|
|
while True:
|
|
if hasattr(unwrap, "__wrapped__"):
|
|
unwrap = unwrap.__wrapped__
|
|
continue
|
|
if isinstance(unwrap, functools.partial):
|
|
unwrap = unwrap.func
|
|
continue
|
|
break
|
|
if hasattr(unwrap, "__globals__"):
|
|
obj_globals = unwrap.__globals__
|
|
|
|
if globals is None:
|
|
globals = obj_globals
|
|
if locals is None:
|
|
locals = obj_locals
|
|
|
|
# "Inject" type parameters into the local namespace
|
|
# (unless they are shadowed by assignments *in* the local namespace),
|
|
# as a way of emulating annotation scopes when calling `eval()`
|
|
if type_params := getattr(obj, "__type_params__", ()):
|
|
if locals is None:
|
|
locals = {}
|
|
locals = {param.__name__: param for param in type_params} | locals
|
|
|
|
return_value = {
|
|
key: value if not isinstance(value, str) else eval(value, globals, locals)
|
|
for key, value in ann.items()
|
|
}
|
|
return return_value
|