Implement JSON dump conversion for torch_dtype in TrainingArguments (#31224)

* Implement JSON dump conversion for torch_dtype in TrainingArguments

* Add unit test for converting torch_dtype in TrainingArguments to JSON

* move unit test for converting torch_dtype into TrainerIntegrationTest class

* reformating using ruff

* convert dict_torch_dtype_to_str to private method _dict_torch_dtype_to_str

---------
Co-authored-by: jun.4 <jun.4@kakaobrain.com>

src/transformers/training_args.py

@@ -2370,6 +2370,18 @@ class TrainingArguments:
         )
         return warmup_steps
 
+    def _dict_torch_dtype_to_str(self, d: Dict[str, Any]) -> None:
+        """
+        Checks whether the passed dictionary and its nested dicts have a *torch_dtype* key and if it's not None,
+        converts torch.dtype to a string of just the type. For example, `torch.float32` get converted into *"float32"*
+        string, which can then be stored in the json format.
+        """
+        if d.get("torch_dtype", None) is not None and not isinstance(d["torch_dtype"], str):
+            d["torch_dtype"] = str(d["torch_dtype"]).split(".")[1]
+        for value in d.values():
+            if isinstance(value, dict):
+                self._dict_torch_dtype_to_str(value)
+
     def to_dict(self):
         """
         Serializes this instance while replace `Enum` by their values (for JSON serialization support). It obfuscates
@@ -2388,6 +2400,8 @@ class TrainingArguments:
             # Handle the accelerator_config if passed
             if is_accelerate_available() and isinstance(v, AcceleratorConfig):
                 d[k] = v.to_dict()
+        self._dict_torch_dtype_to_str(d)
+
         return d
 
     def to_json_string(self):

tests/trainer/test_trainer.py

@@ -3445,6 +3445,35 @@ class TrainerIntegrationTest(TestCasePlus, TrainerIntegrationCommon):
                 )
             self.assertTrue("Tried passing in a callable to `accelerator_config`" in str(context.exception))
 
+    def test_torch_dtype_to_json(self):
+        @dataclasses.dataclass
+        class TorchDtypeTrainingArguments(TrainingArguments):
+            torch_dtype: torch.dtype = dataclasses.field(
+                default=torch.float32,
+            )
+
+        for dtype in [
+            "float32",
+            "float64",
+            "complex64",
+            "complex128",
+            "float16",
+            "bfloat16",
+            "uint8",
+            "int8",
+            "int16",
+            "int32",
+            "int64",
+            "bool",
+        ]:
+            torch_dtype = getattr(torch, dtype)
+            with tempfile.TemporaryDirectory() as tmp_dir:
+                args = TorchDtypeTrainingArguments(output_dir=tmp_dir, torch_dtype=torch_dtype)
+
+                args_dict = args.to_dict()
+                self.assertIn("torch_dtype", args_dict)
+                self.assertEqual(args_dict["torch_dtype"], dtype)
+
 
 @require_torch
 @is_staging_test