Fix automatic parameter IDs for broken __name__ lookup

changelog/14560.bugfix.rst

@@ -0,0 +1 @@
+Fixed automatic parametrization ID generation crashing when a parameter object raises an exception while accessing ``__name__``.

src/_pytest/python.py

@@ -1048,10 +1048,11 @@ def _idval_from_value(self, val: object) -> str | None:
             pass
         elif isinstance(val, enum.Enum):
             return str(val)
-        elif isinstance(getattr(val, "__name__", None), str):
-            # Name of a class, function, module, etc.
-            name: str = getattr(val, "__name__")
-            return name
+        else:
+            name: str | None = safe_getattr(val, "__name__", None)
+            if isinstance(name, str):
+                # Name of a class, function, module, etc.
+                return name
         return None
 
     def _idval_from_value_required(self, val: object, idx: int) -> str:

testing/python/metafunc.py

@@ -425,6 +425,18 @@ def test_function():
                 IdMaker([], [], None, None, None, None)._idval(val, "a", 6) == expected
             )
 
+    def test_idval_ignores_broken_name_attribute(self) -> None:
+        """Use the fallback ID for values that reject __name__ lookup."""
+
+        class DictWrapper(dict[str, object]):
+            def __getattr__(self, name: str) -> object:
+                return self[name]
+
+        assert (
+            IdMaker([], [], None, None, None, None)._idval(DictWrapper(), "a", 6)
+            == "a6"
+        )
+
     def test_notset_idval(self) -> None:
         """Test that a NOTSET value (used by an empty parameterset) generates
         a proper ID.