bpo-43118: Fix bug in inspect.signature around 'base.__text_signature…

…__' (GH-30285) (#30765)

(cherry picked from commit 881a763)

Co-authored-by: Weipeng Hong <hongweichen8888@sina.com>

Co-authored-by: Weipeng Hong <hongweichen8888@sina.com>

Lib/inspect.py

@@ -2511,9 +2511,9 @@ def _signature_from_callable(obj, *,
  pass
  else:
  if text_sig:
- # If 'obj' class has a __text_signature__ attribute:
+ # If 'base' class has a __text_signature__ attribute:
  # return a signature based on it
- return _signature_fromstr(sigcls, obj, text_sig)
+ return _signature_fromstr(sigcls, base, text_sig)
 
  # No '__text_signature__' was found for the 'obj' class.
  # Last option is to check if its '__init__' is

Lib/test/ann_module7.py

@@ -0,0 +1,11 @@
+# Tests class have ``__text_signature__``
+
+from __future__ import annotations
+
+DEFAULT_BUFFER_SIZE = 8192
+
+class BufferedReader(object):
+ """BufferedReader(raw, buffer_size=DEFAULT_BUFFER_SIZE)\n--\n\n
+ Create a new buffered reader using the given readable raw IO object.
+ """
+ pass

Lib/test/test_inspect.py

@@ -4218,6 +4218,17 @@ def func(*args, **kwargs):
  sig = inspect.signature(func)
  self.assertEqual(str(sig), '(self, a, b=1, /, *args, c, d=2, **kwargs)')
 
+ def test_base_class_have_text_signature(self):
+ # see issue 43118
+ from test.ann_module7 import BufferedReader
+ class MyBufferedReader(BufferedReader):
+ """buffer reader class."""
+
+ text_signature = BufferedReader.__text_signature__
+ self.assertEqual(text_signature, '(raw, buffer_size=DEFAULT_BUFFER_SIZE)')
+ sig = inspect.signature(MyBufferedReader)
+ self.assertEqual(str(sig), '(raw, buffer_size=8192)')
+
 
 class NTimesUnwrappable:
  def __init__(self, n):

Misc/NEWS.d/next/Library/2021-12-29-14-42-09.bpo-43118.BoVi_5.rst

@@ -0,0 +1,3 @@
+Fix a bug in :func:`inspect.signature` that was causing it to fail on some
+subclasses of classes with a ``__text_signature__`` referencing module
+globals. Patch by Weipeng Hong.