Support functools.partialmethod annotate functions

Author: dr-carlos

Lib/annotationlib.py

@@ -905,7 +905,7 @@ def _get_annotate_attr(annotate, attr, default):
         (functools := sys.modules.get("functools", None))
         and isinstance(annotate, functools.partial)
     ):
-        return getattr(annotate.func, attr, default)
+        return _get_annotate_attr(annotate.func, attr, default)
 
     return default
 
@@ -929,6 +929,9 @@ def _direct_call_annotate(func, annotate, format):
         # We could call the function directly, but then we'd have to handle placeholders,
         # and this way should be more robust for future changes.
         if isinstance(annotate, functools.partial):
+            # Partial methods
+            if self := getattr(annotate, "__self__", None):
+                return functools.partial(func, self, *annotate.args, **annotate.keywords)(format)
             return functools.partial(func, *annotate.args, **annotate.keywords)(format)
 
     # If annotate is a cached function, we've now updated the function data, so

Lib/test/test_annotationlib.py

@@ -1648,6 +1648,31 @@ def format(format, second, /, *, third, __Format=Format,
 
         self.assertEqual(annotations, {"x": Format.VALUE * 5 * 6})
 
+    def test_callable_partialmethod_annotate_forwardref_value_fallback(self):
+        # If Format.STRING and Format.VALUE_WITH_FAKE_GLOBALS are not
+        # supported fall back to Format.VALUE and convert to strings
+        class Annotate:
+            def _internal_format(self, format, second, /, *, third, __Format=Format,
+                       __NotImplementedError=NotImplementedError):
+                if format == __Format.VALUE:
+                    return {"x": format * second * third}
+                else:
+                    raise __NotImplementedError(format)
+
+            format = functools.partialmethod(
+                _internal_format,
+                functools.Placeholder,
+                5,
+                third=6
+            )
+
+        annotations = annotationlib.call_annotate_function(
+            Annotate().format,
+            Format.FORWARDREF,
+        )
+
+        self.assertEqual(annotations, {"x": Format.VALUE * 5 * 6})
+
     def test_callable_cache_annotate_forwardref_value_fallback(self):
         # If Format.STRING and Format.VALUE_WITH_FAKE_GLOBALS are not
         # supported fall back to Format.VALUE and convert to strings