Use signature (*args, **kwargs) when signature is unavailable (Lightning-AI#2542)

Author: shino16

thunder/core/codeutils.py

@@ -436,7 +436,10 @@ def get_siginfo(fn: Callable, args, kwargs, *, _make_named_inputs: bool = False)
         fn_ = fn_.meta
 
     # Binds args and kwargs to signature
-    sig = inspect.signature(fn_)
+    try:
+        sig = inspect.signature(fn_)
+    except ValueError:
+        sig = inspect.signature(lambda *args, **kwargs: None)
     kwargs.update(partial_kwargs)
     ba = sig.bind(*args, **kwargs)
 

thunder/tests/test_core.py

@@ -1620,6 +1620,19 @@ def bar(__a, __b):
     thunder.trace()(bar, a, b)
 
 
+# Tests if Thunder can trace a function without a valid signature
+@instantiate(dtypes=NOTHING)
+def test_no_signature(executor, device, _):
+    a = make_tensor((2, 3), device=device, dtype=torch.float32)
+
+    fn_trace = thunder.trace()(getattr, a, "mT")
+
+    jfn = executor.make_callable(fn_trace)
+    actual = jfn(a, "mT")
+    expected = getattr(a, "mT")
+    assert_close(actual, expected)
+
+
 @instantiate(dtypes=NOTHING)
 def test_trace_args_no_name_collision(executor, device, _):
     from thunder.core.trace import detached_trace