Update exir_deserialize logic (#15840)

Summary: Pull Request resolved: #15840

Reviewed By: mcremon-meta

Differential Revision: D87112636

Author: ethansfng

exir/serde/export_serialize.py

@@ -2143,17 +2143,21 @@ def deserialize_meta_func(serialized_target: str):
             def import_nn_module_stack(key, path, ty):
                 return key, (path, ty)
 
-            # Helper function that splits strings by commas except for those
-            # encapsulated by parens, which are valid traces.
-            # TODO: Currently this is needed due to indexing Sequential
-            # layers introducing names in the form "layer.slice(1, None, None)".
-            # If that naming is improved, this fancier splitting can probably be
-            # reverted to a simple split by comma.
+            # Helper function to split string by commas, accounting for nested parentheses/brackets
             def metadata_split(metadata):
-                # Remove the parentheses and commas inside them
-                metadata = re.sub(r"\(.*?\)", "", metadata)
-                # Split the string by comma, except for those inside parentheses
-                return re.split(r"(?<!\()\s*,\s*(?!\()", metadata)
+                out = []
+                start, depth = 0, 0
+                for position, char in enumerate(metadata):
+                    if char in "[(":
+                        depth += 1
+                    elif char in ")]":
+                        depth -= 1
+                    elif char == "," and depth == 0:
+                        out.append(metadata[start:position])
+                        start = position + 1
+                out.append(metadata[start:])
+                assert len(out) == 3
+                return out
 
             nn_module_stack = dict(
                 import_nn_module_stack(*metadata_split(item))