config: Don't spam warnings about reference type configs (#145800)

Summary:
https://github.com/pytorch/pytorch/issues/145755

The is_dynamic check for reference types was subtly broken, causing log spam
after it was accessed

Added an explicit type for is_default for reference types to make sure this
behaviour is correct
Pull Request resolved: https://github.com/pytorch/pytorch/pull/145800
Approved by: https://github.com/eellison

test/test_utils_config_module.py

@@ -194,8 +194,7 @@ torch.testing._internal.fake_config_module.e_env_default = True
 torch.testing._internal.fake_config_module.e_env_default_FALSE = False
 torch.testing._internal.fake_config_module.e_env_default_str = '1234'
 torch.testing._internal.fake_config_module.e_env_default_str_empty = ''
-torch.testing._internal.fake_config_module.e_env_force = True
-torch.testing._internal.fake_config_module._save_config_ignore = ['e_ignored']""",
+torch.testing._internal.fake_config_module.e_env_force = True""",
         )
 
     def test_codegen_config_function(self):
@@ -390,6 +389,12 @@ torch.testing._internal.fake_config_module3.e_func = _warnings.warn""",
         with config.patch(e_aliased_bool=True):
             self.assertTrue(config2.e_aliasing_bool)
 
+    def test_reference_is_default(self):
+        t = config.e_dict
+        self.assertTrue(config._is_default("e_dict"))
+        t["a"] = "b"
+        self.assertFalse(config._is_default("e_dict"))
+
 
 if __name__ == "__main__":
     run_tests()

torch/utils/_config_module.py

@@ -9,7 +9,6 @@ import pickle
 import sys
 import tokenize
 import unittest
-import warnings
 from dataclasses import dataclass
 from types import FunctionType, ModuleType
 from typing import (
@@ -444,11 +443,12 @@ class ConfigModule(ModuleType):
             config_val.env_value_force is _UNSET_SENTINEL
             or config_val.env_value_force == config_val.default
         )
-        return (
-            config_val.user_override is _UNSET_SENTINEL
-            and not_set_env_default
-            and not_set_env_force
-        )
+
+        unset = config_val.user_override is _UNSET_SENTINEL
+        # Handle reference types specially to avoid spammy warnings
+        if isinstance(config_val.default, (list, set, dict)):
+            unset = unset or config_val.user_override == config_val.default
+        return unset and not_set_env_default and not_set_env_force
 
     def _get_dict(
         self,
@@ -470,16 +470,11 @@ class ConfigModule(ModuleType):
             ignored_prefixes are prefixes that if a key matches should
                 not be exported
             skip_default does two things. One if a key has not been modified
-                it skips it. The other is it modified the logging behaviour
-                to match what codegen already did for modified skipped keys
+                it skips it.
         """
         config: dict[str, Any] = {}
         for key in self._config:
             if ignored_keys and key in ignored_keys:
-                if skip_default and not self._is_default(key):
-                    warnings.warn(
-                        f"Skipping serialization of {key} value {getattr(self, key)}"
-                    )
                 continue
             if ignored_prefixes:
                 if any(key.startswith(prefix) for prefix in ignored_prefixes):
@@ -611,9 +606,9 @@ class ConfigModule(ModuleType):
             if k in self._config:
                 setattr(self, k, v)
             else:
-                warnings.warn(
-                    f"key {k} with value {v} is not understood by this config"
-                )
+                from torch._dynamo.utils import warn_once
+
+                warn_once(f"key {k} with value {v} is not understood by this config")
 
     def get_config_copy(self) -> dict[str, Any]:
         return self._get_dict()