Preserve card metadata format/ordering on load->save

src/huggingface_hub/repocard.py

@@ -109,7 +109,9 @@ def content(self, content: str):
             data_dict = {}
             self.text = content
 
-        self.data = self.card_data_class(**data_dict, ignore_metadata_errors=self.ignore_metadata_errors)
+        self.data = self.card_data_class(
+            **data_dict, ignore_metadata_errors=self.ignore_metadata_errors, original_order=list(data_dict.keys())
+        )
 
     def __str__(self):
         return self.content

src/huggingface_hub/repocard_data.py

@@ -172,8 +172,12 @@ class CardData:
     inherit from `dict` to allow this export step.
     """
 
-    def __init__(self, ignore_metadata_errors: bool = False, **kwargs):
+    def __init__(self, ignore_metadata_errors: bool = False, original_order: Optional[List[str]] = None, **kwargs):
         self.__dict__.update(kwargs)
+        if original_order:
+            self.__dict__ = {
+                k: self.__dict__[k] for k in original_order + list(set(self.__dict__.keys()) - set(original_order))
+            }
 
     def to_dict(self) -> Dict[str, Any]:
         """Converts CardData to a dict.
@@ -316,6 +320,7 @@ def __init__(
         pipeline_tag: Optional[str] = None,
         tags: Optional[List[str]] = None,
         ignore_metadata_errors: bool = False,
+        original_order: Optional[List[str]] = None,
         **kwargs,
     ):
         self.base_model = base_model
@@ -347,7 +352,7 @@ def __init__(
                         " some information will be lost. Use it at your own risk."
                     )
 
-        super().__init__(**kwargs)
+        super().__init__(**kwargs, original_order=original_order)
 
         if self.eval_results:
             if isinstance(self.eval_results, EvalResult):
@@ -419,6 +424,7 @@ def __init__(
         train_eval_index: Optional[Dict] = None,
         config_names: Optional[Union[str, List[str]]] = None,
         ignore_metadata_errors: bool = False,
+        original_order: Optional[List[str]] = None,
         **kwargs,
     ):
         self.annotations_creators = annotations_creators
@@ -436,7 +442,7 @@ def __init__(
 
         # TODO - maybe handle this similarly to EvalResult?
         self.train_eval_index = train_eval_index or kwargs.pop("train-eval-index", None)
-        super().__init__(**kwargs)
+        super().__init__(**kwargs, original_order=original_order)
 
     def _to_dict(self, data_dict):
         data_dict["train-eval-index"] = data_dict.pop("train_eval_index")
@@ -507,6 +513,7 @@ def __init__(
         datasets: Optional[List[str]] = None,
         tags: Optional[List[str]] = None,
         ignore_metadata_errors: bool = False,
+        original_order: Optional[List[str]] = None,
         **kwargs,
     ):
         self.title = title
@@ -520,7 +527,7 @@ def __init__(
         self.models = models
         self.datasets = datasets
         self.tags = _to_unique_list(tags)
-        super().__init__(**kwargs)
+        super().__init__(**kwargs, original_order=original_order)
 
 
 def model_index_to_eval_results(model_index: List[Dict[str, Any]]) -> Tuple[str, List[EvalResult]]:

tests/test_repocard.py

@@ -847,6 +847,12 @@ def test_model_card_from_template_eval_results(self):
         self.assertTrue(card.data.to_dict().get("eval_results") is None)
         self.assertEqual(str(card)[: len(DUMMY_MODELCARD_EVAL_RESULT)], DUMMY_MODELCARD_EVAL_RESULT)
 
+    def test_preserve_order_load_save(self):
+        model_card = ModelCard(DUMMY_MODELCARD)
+        model_card.data.license = "test"
+        model_card.content
+        self.assertEqual(model_card.content, "---\nlicense: test\ndatasets:\n- foo\n- bar\n---\n\nHello\n")
+
 
 class DatasetCardTest(TestCaseWithHfApi):
     def test_load_datasetcard_from_file(self):