GH-96073: Fix wild replacement in inspect.formatannotation (#96074)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Lib/inspect.py

@@ -1433,7 +1433,10 @@ def getargvalues(frame):
 
 def formatannotation(annotation, base_module=None):
     if getattr(annotation, '__module__', None) == 'typing':
-        return repr(annotation).replace('typing.', '')
+        def repl(match):
+            text = match.group()
+            return text.removeprefix('typing.')
+        return re.sub(r'[\w\.]+', repl, repr(annotation))
     if isinstance(annotation, types.GenericAlias):
         return str(annotation)
     if isinstance(annotation, type):

Lib/test/test_inspect.py

@@ -1421,6 +1421,13 @@ def wrapper(a, b):
         self.assertEqual(inspect.get_annotations(isa.MyClassWithLocalAnnotations, eval_str=True), {'x': int})
 
 
+class TestFormatAnnotation(unittest.TestCase):
+    def test_typing_replacement(self):
+        from test.typinganndata.ann_module9 import ann, ann1
+        self.assertEqual(inspect.formatannotation(ann), 'Union[List[str], int]')
+        self.assertEqual(inspect.formatannotation(ann1), 'Union[List[testModule.typing.A], int]')
+
+
 class TestIsDataDescriptor(unittest.TestCase):
 
     def test_custom_descriptors(self):

Lib/test/typinganndata/ann_module9.py

@@ -0,0 +1,14 @@
+# Test ``inspect.formatannotation``
+# https://github.com/python/cpython/issues/96073
+
+from typing import Union, List
+
+ann = Union[List[str], int]
+
+# mock typing._type_repr behaviour
+class A: ...
+
+A.__module__ = 'testModule.typing'
+A.__qualname__ = 'A'
+
+ann1 = Union[List[A], int]

Misc/NEWS.d/next/Library/2022-08-29-12-35-28.gh-issue-96073.WaGstf.rst

@@ -0,0 +1 @@
+In :mod:`inspect`, fix overeager replacement of "`typing.`" in formatting annotations.