Fix strip_function_call in GuardBuilder (pytorch#97810)

repo:
from pytorch#92670 this address one of the bug for TorchDynamo

pytest ./generated/test_PeterouZh_CIPS_3D.py -k test_003

Issue:
In GuardBuilder, when parsing argnames with "getattr(a.layers[slice(2)][0]._abc, '0')" it returns "getattr(a", where it suppose to return "a", and thus causing SyntaxError.

This PR fix the regex and add couple test cases.

Fixes #ISSUE_NUMBER

Pull Request resolved: pytorch#97810
Approved by: https://github.com/yanboliang

test/dynamo/test_misc.py

@@ -5231,6 +5231,21 @@ def forward(self, input):
                 prof.report()
             )
 
+    def test_guards_strip_function_call(self):
+        from torch._dynamo.guards import strip_function_call
+
+        test_case = [
+            ("___odict_getitem(a, 1)", "a"),
+            ("a.layers[slice(2)][0]._xyz", "a"),
+            ("getattr(a.layers[slice(2)][0]._abc, '0')", "a"),
+            ("getattr(getattr(a.x[3], '0'), '3')", "a"),
+            ("a.layers[slice(None, -1, None)][0]._xyz", "a"),
+            ("a.layers[func('offset', -1, None)][0]._xyz", "a"),
+        ]
+        # strip_function_call should extract the object from the string.
+        for name, expect_obj in test_case:
+            self.assertEqual(strip_function_call(name), expect_obj)
+
 
 class CustomFunc1(torch.autograd.Function):
     @staticmethod

torch/_dynamo/guards.py

@@ -67,10 +67,23 @@
 def strip_function_call(name):
     """
     "___odict_getitem(a, 1)" => "a"
+    "a.layers[slice(2)][0]._xyz" ==> "a"
+    "getattr(a.layers[slice(2)][0]._abc, '0')" ==> "a"
+    "getattr(getattr(a.x[3], '0'), '3')" ==> "a"
+    "a.layers[slice(None, -1, None)][0]._xyz" ==> "a"
     """
-    m = re.search(r"([a-z0-9_]+)\(([^(),]+)[^()]*\)", name)
-    if m and m.group(1) != "slice":
-        return strip_function_call(m.group(2))
+    # recursively find valid object name in fuction
+    valid_name = re.compile("[A-Za-z_].*")
+    curr = ""
+    for char in name:
+        if char in " (":
+            curr = ""
+        elif char in "),[]":
+            if curr and curr != "None" and valid_name.match(curr):
+                return strip_function_call(curr)
+        else:
+            curr += char
+
     return strip_getattr_getitem(name)