gh-103449: Fix a bug in dataclass docstring generation (#103454)

diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 4026c8b77975b7df2f4f94bab13daec48d5dc124..a73cdc22a5f4b34405a2cc76071d9dbe1ed3a596 100644 (file)
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1128,8 +1128,13 @@ 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', ''))
+        try:
+            # 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 (TypeError, ValueError):
+            text_sig = ''
+        cls.__doc__ = (cls.__name__ + text_sig)
 
     if match_args:
         # I could probably compute this once

diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index 6888680105c4fdf912921a56b5ab140cf00c7dcc..ae8bfcc149e86216082ef6e21b727b22035d0a28 100644 (file)
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -2297,6 +2297,19 @@ class TestDocString(unittest.TestCase):
 
         self.assertDocStrEqual(C.__doc__, "C(x:collections.deque=<factory>)")
 
+    def test_docstring_with_no_signature(self):
+        # See https://github.com/python/cpython/issues/103449
+        class Meta(type):
+            __call__ = dict
+        class Base(metaclass=Meta):
+            pass
+
+        @dataclass
+        class C(Base):
+            pass
+
+        self.assertDocStrEqual(C.__doc__, "C")
+
 
 class TestInit(unittest.TestCase):
     def test_base_has_init(self):

diff --git a/Misc/NEWS.d/next/Library/2023-04-11-21-38-39.gh-issue-103449.-nxmhb.rst b/Misc/NEWS.d/next/Library/2023-04-11-21-38-39.gh-issue-103449.-nxmhb.rst
new file mode 100644 (file)
index 0000000..0b2b47a
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-04-11-21-38-39.gh-issue-103449.-nxmhb.rst
@@ -0,0 +1 @@
+Fix a bug in doc string generation in :func:`dataclasses.dataclass`.