pythongh-128184: Fix docstring generation in dataclasses with forward…

… refs

Lib/dataclasses.py

@@ -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:
+            # 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)

Lib/test/test_dataclasses/__init__.py

@@ -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
@@ -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) -> None: ...
+                """,
+            ),
+            ns,
+        )
+
+        self.assertDocStrEqual(ns['C'].__doc__, "C(x:'X')")
+
     def test_docstring_with_no_signature(self):
         # See https://github.com/python/cpython/issues/103449
         class Meta(type):

Misc/NEWS.d/next/Library/2024-12-23-17-00-35.gh-issue-128184.cRQvgM.rst

@@ -0,0 +1,2 @@
+Fixes :exc:`NameError` when using :func:`dataclasses.dataclass` on classes
+with unresolvable forward references.