Support for default_factory in cmd_conf (pytorch#3167)

Summary:
Pull Request resolved: pytorch#3167

The cmd_conf decorator now properly handles dataclass fields with default_factory by calling the factory function to get the actual default value. This ensures dataclass fields recieve their intended default values when using argparse instead of missing type objects.

Reviewed By: aliafzal

Differential Revision: D77896269

fbshipit-source-id: 446ae84b1728d1786031c62527bf76bbf22059dc

Author: SSYernar

torchrec/distributed/benchmark/benchmark_utils.py

@@ -20,7 +20,7 @@
 import os
 import time
 import timeit
-from dataclasses import dataclass, fields, is_dataclass
+from dataclasses import dataclass, fields, is_dataclass, MISSING
 from enum import Enum
 from typing import (
     Any,
@@ -500,8 +500,15 @@ def wrapper() -> Any:
                         ftype = non_none[0]
                         origin = get_origin(ftype)
 
+                # Handle default_factory value
+                default_value = (
+                    f.default_factory()  # pyre-ignore [29]
+                    if f.default_factory is not MISSING
+                    else f.default
+                )
+
                 arg_kwargs = {
-                    "default": f.default,
+                    "default": default_value,
                     "help": f"({cls.__name__}) {arg_name}",
                 }