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gh-128184: Fix docstring generation in dataclasses with forward refs #128194

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gh-128184: Fix docstring generation in dataclasses with forward refs #128194

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gh-128184: Fix docstring generation in dataclasses with forward refs
sobolevn Dec 23, 2024
bdfea9f
Also check existing type
sobolevn Dec 25, 2024
d8c6a7f
Merge branch 'main' into issue-128184
sobolevn Feb 19, 2025
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7 changes: 7 additions & 0 deletions Lib/dataclasses.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1164,6 +1164,13 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
# In some cases fetching a signature is not possible.
# But, we surely should not fail in this case.
text_sig = str(inspect.signature(cls)).replace(' -> None', '')
except NameError:
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Why not just start with SOURCE format? I don't think we need to catch NameError first.

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When we do that, a lot of tests fail with similar messages:

    def test_docstring_two_fields(self):
        @dataclass
        class C:
            x: int
            y: int

        self.assertDocStrEqual(C.__doc__, "C(x:int, y:int)")

Produces:

======================================================================
FAIL: test_docstring_two_fields (test.test_dataclasses.TestDocString.test_docstring_two_fields)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython2/Lib/test/test_dataclasses/__init__.py", line 2294, in test_docstring_two_fields
    self.assertDocStrEqual(C.__doc__, "C(x:int, y:int)")
    ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython2/Lib/test/test_dataclasses/__init__.py", line 2263, in assertDocStrEqual
    self.assertEqual(a.replace(' ', ''), b.replace(' ', ''))
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: "C(x:'__dataclass_type_x__',y:'__dataclas[46 chars]e__'" != 'C(x:int,y:int)'
- C(x:'__dataclass_type_x__',y:'__dataclass_type_y__')->'__dataclass___init___return_type__'
+ C(x:int,y:int)

I am not quite sure - why.

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I tried that again and it still does not work without NameError handling.

This happens because of:

locals = {**{f'__dataclass_type_{f.name}__': f.type for f in fields},
              **{'__dataclass_HAS_DEFAULT_FACTORY__': _HAS_DEFAULT_FACTORY,
                 '__dataclass_builtins_object__': object,
                 }
              }

So, I am not sure that this is totally correct.

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@JelleZijlstra what do you think?

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I thought about this more and came up with a more general improvement: #130815. This also makes the docstring cleaner for dataclasses with no __init__ that contain unresolved names, and it improves other uses of inspect.signature. Please take a look.

# This means that some types where not defined, maybe due to
# forward references, etc. In this case, try different format.
text_sig = str(inspect.signature(
cls,
annotation_format=annotationlib.Format.STRING,
)).replace(" -> 'None'", '')
except (TypeError, ValueError):
text_sig = ''
cls.__doc__ = (cls.__name__ + text_sig)
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19 changes: 19 additions & 0 deletions Lib/test/test_dataclasses/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
import types
import weakref
import traceback
import textwrap
import unittest
from unittest.mock import Mock
from typing import ClassVar, Any, List, Union, Tuple, Dict, Generic, TypeVar, Optional, Protocol, DefaultDict
Expand Down Expand Up @@ -2343,6 +2344,24 @@ class C:

self.assertDocStrEqual(C.__doc__, "C(x:collections.deque=<factory>)")

def test_docstring_with_unsolvable_forward_ref_in_init(self):
# See: https://github.com/python/cpython/issues/128184
ns = {}
exec(
textwrap.dedent(
"""
from dataclasses import dataclass

@dataclass
class C:
def __init__(self, x: X, num: int) -> None: ...
""",
),
ns,
)

self.assertDocStrEqual(ns['C'].__doc__, "C(x:'X',num:'int')")

def test_docstring_with_no_signature(self):
# See https://github.com/python/cpython/issues/103449
class Meta(type):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2024-12-23-17-00-35.gh-issue-128184.cRQvgM.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fixes :exc:`NameError` when using :func:`dataclasses.dataclass` on classes
with unresolvable forward references.
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