Merge pull request #7632 from eric-wieser/better-inspect-failure

Do not crash if `is_builtin_class_method` is passed a non-type

sphinx/util/inspect.py

@@ -389,12 +389,23 @@ def is_builtin_class_method(obj: Any, attr_name: str) -> bool:
     Why this function needed? CPython implements int.__init__ by Descriptor
     but PyPy implements it by pure Python code.
     """
-    classes = [c for c in inspect.getmro(obj) if attr_name in c.__dict__]
-    cls = classes[0] if classes else object
-
-    if not hasattr(builtins, safe_getattr(cls, '__name__', '')):
+    try:
+        mro = inspect.getmro(obj)
+    except AttributeError:
+        # no __mro__, assume the object has no methods as we know them
         return False
-    return getattr(builtins, safe_getattr(cls, '__name__', '')) is cls
+
+    try:
+        cls = next(c for c in mro if attr_name in safe_getattr(c, '__dict__', {}))
+    except StopIteration:
+        return False
+
+    try:
+        name = safe_getattr(cls, '__name__')
+    except AttributeError:
+        return False
+
+    return getattr(builtins, name, None) is cls
 
 
 def signature(subject: Callable, bound_method: bool = False) -> inspect.Signature:

tests/test_util_inspect.py

@@ -18,7 +18,7 @@ from inspect import Parameter
 import pytest
 
 from sphinx.util import inspect
-from sphinx.util.inspect import stringify_signature
+from sphinx.util.inspect import stringify_signature, is_builtin_class_method
 
 
 def test_signature():
@@ -579,3 +579,21 @@ def test_getdoc_inherited_decorated_method():
 
     assert inspect.getdoc(Bar.meth, getattr, False, Bar, "meth") is None
     assert inspect.getdoc(Bar.meth, getattr, True, Bar, "meth") == "docstring."
+
+
+def test_is_builtin_class_method():
+    class MyInt(int):
+        def my_method(self):
+            pass
+
+    assert inspect.is_builtin_class_method(MyInt, 'to_bytes')
+    assert inspect.is_builtin_class_method(MyInt, '__init__')
+    assert not inspect.is_builtin_class_method(MyInt, 'my_method')
+    assert not inspect.is_builtin_class_method(MyInt, 'does_not_exist')
+    assert not inspect.is_builtin_class_method(4, 'still does not crash')
+
+    class ObjectWithMroAttr:
+        def __init__(self, mro_attr):
+            self.__mro__ = mro_attr
+
+    assert not inspect.is_builtin_class_method(ObjectWithMroAttr([1, 2, 3]), 'still does not crash')