[dynamo] support operator.methodcaller (pytorch#141137)

Pull Request resolved: pytorch#141137
Approved by: https://github.com/jansel
ghstack dependencies: pytorch#141122

Author: XuehaiPan

test/dynamo/test_functions.py

@@ -3109,6 +3109,25 @@ def fn(x, y):
                 y = torch.randn(3, 4)
                 self.assertEqual(opt_fn(x, y), fn(x, y))
 
+    def test_methodcaller(self):
+        for name, args, kwargs in (
+            ("size", (), {}),
+            ("size", (0,), {}),
+            ("add", (torch.randn(3, 4),), {}),
+            ("add", (torch.randn(3, 4),), {"alpha": 2.0}),
+        ):
+            with self.subTest(name=name, args=args, kwargs=kwargs):
+
+                def fn(x, y):
+                    caller = operator.methodcaller(name, *args, **kwargs)
+                    return caller(x), caller(y)
+
+                opt_fn = torch.compile(fullgraph=True)(fn)
+
+                x = torch.randn(3, 4)
+                y = torch.randn(3, 4)
+                self.assertEqual(opt_fn(x, y), fn(x, y))
+
     def gen_random_range_args(self):
         args_count = random.randint(1, 3)
         args = [random.randint(-10, 10) for _ in range(args_count)]

torch/_dynamo/polyfills/operator.py

@@ -12,7 +12,7 @@
 
 
 # Most unary and binary operators are handled by BuiltinVariable (e.g., `pos`, `add`)
-__all__ = ["attrgetter", "itemgetter"]
+__all__ = ["attrgetter", "itemgetter", "methodcaller"]
 
 
 _T = TypeVar("_T")
@@ -95,3 +95,15 @@ def getter(obj: Any) -> tuple[Any, ...]:  # type: ignore[misc]
             return tuple(obj[item] for item in items)
 
     return getter
+
+
+# Reference: https://docs.python.org/3/library/operator.html#operator.methodcaller
+@substitute_in_graph(operator.methodcaller, is_embedded_type=True)  # type: ignore[arg-type]
+def methodcaller(name: str, /, *args: Any, **kwargs: Any) -> Callable[[Any], Any]:
+    if not isinstance(name, str):
+        raise TypeError("method name must be a string")
+
+    def caller(obj: Any) -> Any:
+        return getattr(obj, name)(*args, **kwargs)
+
+    return caller