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GeezerVison is showing github.com — bpo-38605: Make postponed evaluation of annotations default by isidentical · Pull Request #20434 · python/cpython

bpo-38605: Make postponed evaluation of annotations default #20434

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Merged
gvanrossum merged 18 commits into python:master from isidentical:bpo-38605
Oct 6, 2020

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Merged

bpo-38605: Make postponed evaluation of annotations default #20434

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4c5b314
make future annotations default
isidentical May 27, 2020
3402877
Fix test_coroutines
isidentical May 27, 2020
9a131a2
Regenerate bytecode for test_dis
isidentical May 27, 2020
fdcea4d
Regenerate static strings for docxmlrpc and pydoc tests
isidentical May 27, 2020
14e7c2d
Update tests for: syntax, opcodes, posonly, grammar...
isidentical May 27, 2020
f217d48
Refactor inspect tests(+doctests) with string annotations
isidentical May 27, 2020
6209fa0
Add documentation, tests for annotations
isidentical May 27, 2020
bbf01bb
Escape double stringified annotations on typing.ForwardRef
isidentical May 27, 2020
246577d
Fix test_dataclassess
isidentical May 27, 2020
1d77917
Initial attempt for typing fix
isidentical May 29, 2020
6bd5fee
Rename test, apply doc suggestion
isidentical May 29, 2020
1e2c3f8
Adapt code into the latest changes
isidentical Oct 1, 2020
0a04da8
Support double-stringified annotations in dataclasses
isidentical Oct 3, 2020
6d1feb5
Use get_type_hints in inspect.signature
isidentical Oct 4, 2020
86181e4
remove reduntant test
isidentical Oct 4, 2020
4276284
Add what's new entry
isidentical Oct 5, 2020
5ae4bd1
mention about inspect.signature
isidentical Oct 5, 2020
1e73aa7
Tweak what's new words
gvanrossum Oct 6, 2020
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10 changes: 3 additions & 7 deletions 10 Doc/reference/compound_stmts.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -610,13 +610,9 @@ following the parameter name. Any parameter may have an annotation, even those
``*identifier`` or ``**identifier``. Functions may have "return" annotation of
the form "``-> expression``" after the parameter list. These annotations can be
any valid Python expression. The presence of annotations does not change the
semantics of a function. The annotation values are available as values of
a dictionary keyed by the parameters' names in the :attr:`__annotations__`
attribute of the function object. If the ``annotations`` import from
:mod:`__future__` is used, annotations are preserved as strings at runtime which
enables postponed evaluation. Otherwise, they are evaluated when the function
definition is executed. In this case annotations may be evaluated in
a different order than they appear in the source code.
semantics of a function. The annotation values are available as string values
in a dictionary keyed by the parameters' names in the :attr:`__annotations__`
attribute of the function object.

.. index:: pair: lambda; expression

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17 changes: 17 additions & 0 deletions 17 Doc/whatsnew/3.10.rst
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Expand Up @@ -70,6 +70,23 @@ Summary -- Release highlights
New Features
============

.. _whatsnew310-pep563:

PEP 563: Postponed Evaluation of Annotations Becomes Default
------------------------------------------------------------

In Python 3.7, postponed evaluation of annotations was added,
to be enabled with a ``from __future__ import annotations``
directive. In 3.10 this became the default behavior, even
without that future directive. With this being default, all
annotations stored in :attr:`__annotations__` will be strings.
If needed, annotations can be resolved at runtime using
:func:`typing.get_type_hints`. See :pep:`563` for a full
description. Also, the :func:`inspect.signature` will try to
resolve types from now on, and when it fails it will fall back to
showing the string annotations. (Contributed by Batuhan Taskaya
in :issue:`38605`.)

* The :class:`int` type has a new method :meth:`int.bit_count`, returning the
number of ones in the binary expansion of a given integer, also known
as the population count. (Contributed by Niklas Fiekas in :issue:`29882`.)
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13 changes: 10 additions & 3 deletions 13 Lib/dataclasses.py
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Expand Up @@ -398,8 +398,10 @@ def _create_fn(name, args, body, *, globals=None, locals=None,

ns = {}
exec(txt, globals, ns)
return ns['__create_fn__'](**locals)

func = ns['__create_fn__'](**locals)
for arg, annotation in func.__annotations__.copy().items():
func.__annotations__[arg] = locals[annotation]
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return func

def _field_assign(frozen, name, value, self_name):
# If we're a frozen class, then assign to our fields in __init__
Expand Down Expand Up @@ -650,6 +652,11 @@ def _is_type(annotation, cls, a_module, a_type, is_type_predicate):
# a eval() penalty for every single field of every dataclass
# that's defined. It was judged not worth it.

# Strip away the extra quotes as a result of double-stringifying when the
# 'annotations' feature became default.
if annotation.startswith(("'", '"')) and annotation.endswith(("'", '"')):
annotation = annotation[1:-1]

match = _MODULE_IDENTIFIER_RE.match(annotation)
if match:
ns = None
Expand Down Expand Up @@ -990,7 +997,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
if not getattr(cls, '__doc__'):
# Create a class doc-string.
cls.__doc__ = (cls.__name__ +
str(inspect.signature(cls)).replace(' -> None', ''))
str(inspect.signature(cls)).replace(' -> NoneType', ''))
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return cls

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19 changes: 17 additions & 2 deletions 19 Lib/inspect.py
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Expand Up @@ -45,6 +45,7 @@
import tokenize
import token
import types
import typing
import warnings
import functools
import builtins
Expand Down Expand Up @@ -1877,7 +1878,10 @@ def _signature_is_functionlike(obj):
code = getattr(obj, '__code__', None)
defaults = getattr(obj, '__defaults__', _void) # Important to use _void ...
kwdefaults = getattr(obj, '__kwdefaults__', _void) # ... and not None here
annotations = getattr(obj, '__annotations__', None)
try:
annotations = _get_type_hints(obj)
except AttributeError:
annotations = None

return (isinstance(code, types.CodeType) and
isinstance(name, str) and
Expand Down Expand Up @@ -2118,6 +2122,16 @@ def p(name_node, default_node, default=empty):

return cls(parameters, return_annotation=cls.empty)

def _get_type_hints(func):
try:
return typing.get_type_hints(func)
except Exception:
# First, try to use the get_type_hints to resolve
# annotations. But for keeping the behavior intact
# if there was a problem with that (like the namespace
# can't resolve some annotation) continue to use
# string annotations
return func.__annotations__
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def _signature_from_builtin(cls, func, skip_bound_arg=True):
"""Private helper function to get signature for
Expand Down Expand Up @@ -2161,7 +2175,8 @@ def _signature_from_function(cls, func, skip_bound_arg=True):
positional = arg_names[:pos_count]
keyword_only_count = func_code.co_kwonlyargcount
keyword_only = arg_names[pos_count:pos_count + keyword_only_count]
annotations = func.__annotations__
annotations = _get_type_hints(func)

defaults = func.__defaults__
kwdefaults = func.__kwdefaults__

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6 changes: 0 additions & 6 deletions 6 Lib/test/dataclass_module_1.py
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@@ -1,9 +1,3 @@
#from __future__ import annotations
USING_STRINGS = False

# dataclass_module_1.py and dataclass_module_1_str.py are identical
# except only the latter uses string annotations.

import dataclasses
import typing

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32 changes: 0 additions & 32 deletions 32 Lib/test/dataclass_module_1_str.py
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6 changes: 0 additions & 6 deletions 6 Lib/test/dataclass_module_2.py
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@@ -1,9 +1,3 @@
#from __future__ import annotations
USING_STRINGS = False

# dataclass_module_2.py and dataclass_module_2_str.py are identical
# except only the latter uses string annotations.

from dataclasses import dataclass, InitVar
from typing import ClassVar

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32 changes: 0 additions & 32 deletions 32 Lib/test/dataclass_module_2_str.py
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2 changes: 0 additions & 2 deletions 2 Lib/test/dataclass_textanno.py
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@@ -1,5 +1,3 @@
from __future__ import annotations

import dataclasses


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