[Core] fix variant-identification. (#9253)

* fix variant-idenitification.

* fix variant

* fix sharded variant checkpoint loading.

* Apply suggestions from code review

* fixes.

* more fixes.

* remove print.

* fixes

* fixes

* comments

* fixes

* apply suggestions.

* hub_utils.py

* fix test

* updates

* fixes

* fixes

* Apply suggestions from code review

Co-authored-by: YiYi Xu <yixu310@gmail.com>

* updates.

* removep patch file.

---------

Co-authored-by: YiYi Xu <yixu310@gmail.com>

Author: sayakpaul

src/diffusers/models/model_loading_utils.py

@@ -31,6 +31,7 @@
     WEIGHTS_INDEX_NAME,
     _add_variant,
     _get_model_file,
+    deprecate,
     is_accelerate_available,
     is_torch_version,
     logging,
@@ -228,3 +229,67 @@ def _fetch_index_file(
             index_file = None
 
     return index_file
+
+
+def _fetch_index_file_legacy(
+    is_local,
+    pretrained_model_name_or_path,
+    subfolder,
+    use_safetensors,
+    cache_dir,
+    variant,
+    force_download,
+    proxies,
+    local_files_only,
+    token,
+    revision,
+    user_agent,
+    commit_hash,
+):
+    if is_local:
+        index_file = Path(
+            pretrained_model_name_or_path,
+            subfolder or "",
+            SAFE_WEIGHTS_INDEX_NAME if use_safetensors else WEIGHTS_INDEX_NAME,
+        ).as_posix()
+        splits = index_file.split(".")
+        split_index = -3 if ".cache" in index_file else -2
+        splits = splits[:-split_index] + [variant] + splits[-split_index:]
+        index_file = ".".join(splits)
+        if os.path.exists(index_file):
+            deprecation_message = f"This serialization format is now deprecated to standardize the serialization format between `transformers` and `diffusers`. We recommend you to remove the existing files associated with the current variant ({variant}) and re-obtain them by running a `save_pretrained()`."
+            deprecate("legacy_sharded_ckpts_with_variant", "1.0.0", deprecation_message, standard_warn=False)
+            index_file = Path(index_file)
+        else:
+            index_file = None
+    else:
+        if variant is not None:
+            index_file_in_repo = Path(
+                subfolder or "",
+                SAFE_WEIGHTS_INDEX_NAME if use_safetensors else WEIGHTS_INDEX_NAME,
+            ).as_posix()
+            splits = index_file_in_repo.split(".")
+            split_index = -2
+            splits = splits[:-split_index] + [variant] + splits[-split_index:]
+            index_file_in_repo = ".".join(splits)
+            try:
+                index_file = _get_model_file(
+                    pretrained_model_name_or_path,
+                    weights_name=index_file_in_repo,
+                    cache_dir=cache_dir,
+                    force_download=force_download,
+                    proxies=proxies,
+                    local_files_only=local_files_only,
+                    token=token,
+                    revision=revision,
+                    subfolder=None,
+                    user_agent=user_agent,
+                    commit_hash=commit_hash,
+                )
+                index_file = Path(index_file)
+                deprecation_message = f"This serialization format is now deprecated to standardize the serialization format between `transformers` and `diffusers`. We recommend you to remove the existing files associated with the current variant ({variant}) and re-obtain them by running a `save_pretrained()`."
+                deprecate("legacy_sharded_ckpts_with_variant", "1.0.0", deprecation_message, standard_warn=False)
+            except (EntryNotFoundError, EnvironmentError):
+                index_file = None
+
+    return index_file

src/diffusers/models/modeling_utils.py

@@ -54,6 +54,7 @@
 from .model_loading_utils import (
     _determine_device_map,
     _fetch_index_file,
+    _fetch_index_file_legacy,
     _load_state_dict_into_model,
     load_model_dict_into_meta,
     load_state_dict,
@@ -309,11 +310,9 @@ def save_pretrained(
 
         weights_name = SAFETENSORS_WEIGHTS_NAME if safe_serialization else WEIGHTS_NAME
         weights_name = _add_variant(weights_name, variant)
-        weight_name_split = weights_name.split(".")
-        if len(weight_name_split) in [2, 3]:
-            weights_name_pattern = weight_name_split[0] + "{suffix}." + ".".join(weight_name_split[1:])
-        else:
-            raise ValueError(f"Invalid {weights_name} provided.")
+        weights_name_pattern = weights_name.replace(".bin", "{suffix}.bin").replace(
+            ".safetensors", "{suffix}.safetensors"
+        )
 
         os.makedirs(save_directory, exist_ok=True)
 
@@ -624,21 +623,26 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
         is_sharded = False
         index_file = None
         is_local = os.path.isdir(pretrained_model_name_or_path)
-        index_file = _fetch_index_file(
-            is_local=is_local,
-            pretrained_model_name_or_path=pretrained_model_name_or_path,
-            subfolder=subfolder or "",
-            use_safetensors=use_safetensors,
-            cache_dir=cache_dir,
-            variant=variant,
-            force_download=force_download,
-            proxies=proxies,
-            local_files_only=local_files_only,
-            token=token,
-            revision=revision,
-            user_agent=user_agent,
-            commit_hash=commit_hash,
-        )
+        index_file_kwargs = {
+            "is_local": is_local,
+            "pretrained_model_name_or_path": pretrained_model_name_or_path,
+            "subfolder": subfolder or "",
+            "use_safetensors": use_safetensors,
+            "cache_dir": cache_dir,
+            "variant": variant,
+            "force_download": force_download,
+            "proxies": proxies,
+            "local_files_only": local_files_only,
+            "token": token,
+            "revision": revision,
+            "user_agent": user_agent,
+            "commit_hash": commit_hash,
+        }
+        index_file = _fetch_index_file(**index_file_kwargs)
+        # In case the index file was not found we still have to consider the legacy format.
+        # this becomes applicable when the variant is not None.
+        if variant is not None and (index_file is None or not os.path.exists(index_file)):
+            index_file = _fetch_index_file_legacy(**index_file_kwargs)
         if index_file is not None and index_file.is_file():
             is_sharded = True
 

src/diffusers/pipelines/pipeline_utils.py

@@ -50,15 +50,14 @@
     DEPRECATED_REVISION_ARGS,
     BaseOutput,
     PushToHubMixin,
-    deprecate,
     is_accelerate_available,
     is_accelerate_version,
     is_torch_npu_available,
     is_torch_version,
     logging,
     numpy_to_pil,
 )
-from ..utils.hub_utils import load_or_create_model_card, populate_model_card
+from ..utils.hub_utils import _check_legacy_sharding_variant_format, load_or_create_model_card, populate_model_card
 from ..utils.torch_utils import is_compiled_module
 
 
@@ -735,6 +734,21 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
         else:
             cached_folder = pretrained_model_name_or_path
 
+        # The variant filenames can have the legacy sharding checkpoint format that we check and throw
+        # a warning if detected.
+        if variant is not None and _check_legacy_sharding_variant_format(folder=cached_folder, variant=variant):
+            warn_msg = (
+                f"Warning: The repository contains sharded checkpoints for variant '{variant}' maybe in a deprecated format. "
+                "Please check your files carefully:\n\n"
+                "- Correct format example: diffusion_pytorch_model.fp16-00003-of-00003.safetensors\n"
+                "- Deprecated format example: diffusion_pytorch_model-00001-of-00002.fp16.safetensors\n\n"
+                "If you find any files in the deprecated format:\n"
+                "1. Remove all existing checkpoint files for this variant.\n"
+                "2. Re-obtain the correct files by running `save_pretrained()`.\n\n"
+                "This will ensure you're using the most up-to-date and compatible checkpoint format."
+            )
+            logger.warning(warn_msg)
+
         config_dict = cls.load_config(cached_folder)
 
         # pop out "_ignore_files" as it is only needed for download
@@ -745,6 +759,9 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
         # Example: `diffusion_pytorch_model.safetensors` -> `diffusion_pytorch_model.fp16.safetensors`
         # with variant being `"fp16"`.
         model_variants = _identify_model_variants(folder=cached_folder, variant=variant, config=config_dict)
+        if len(model_variants) == 0 and variant is not None:
+            error_message = f"You are trying to load the model files of the `variant={variant}`, but no such modeling files are available."
+            raise ValueError(error_message)
 
         # 3. Load the pipeline class, if using custom module then load it from the hub
         # if we load from explicit class, let's use it
@@ -1251,6 +1268,22 @@ def download(cls, pretrained_model_name, **kwargs) -> Union[str, os.PathLike]:
                 model_info_call_error = e  # save error to reraise it if model is not cached locally
 
         if not local_files_only:
+            filenames = {sibling.rfilename for sibling in info.siblings}
+            if variant is not None and _check_legacy_sharding_variant_format(filenames=filenames, variant=variant):
+                warn_msg = (
+                    f"Warning: The repository contains sharded checkpoints for variant '{variant}' maybe in a deprecated format. "
+                    "Please check your files carefully:\n\n"
+                    "- Correct format example: diffusion_pytorch_model.fp16-00003-of-00003.safetensors\n"
+                    "- Deprecated format example: diffusion_pytorch_model-00001-of-00002.fp16.safetensors\n\n"
+                    "If you find any files in the deprecated format:\n"
+                    "1. Remove all existing checkpoint files for this variant.\n"
+                    "2. Re-obtain the correct files by running `save_pretrained()`.\n\n"
+                    "This will ensure you're using the most up-to-date and compatible checkpoint format."
+                )
+                logger.warning(warn_msg)
+
+            model_filenames, variant_filenames = variant_compatible_siblings(filenames, variant=variant)
+
             config_file = hf_hub_download(
                 pretrained_model_name,
                 cls.config_name,
@@ -1267,9 +1300,6 @@ def download(cls, pretrained_model_name, **kwargs) -> Union[str, os.PathLike]:
             # retrieve all folder_names that contain relevant files
             folder_names = [k for k, v in config_dict.items() if isinstance(v, list) and k != "_class_name"]
 
-            filenames = {sibling.rfilename for sibling in info.siblings}
-            model_filenames, variant_filenames = variant_compatible_siblings(filenames, variant=variant)
-
             diffusers_module = importlib.import_module(__name__.split(".")[0])
             pipelines = getattr(diffusers_module, "pipelines")
 
@@ -1292,13 +1322,8 @@ def download(cls, pretrained_model_name, **kwargs) -> Union[str, os.PathLike]:
                     )
 
             if len(variant_filenames) == 0 and variant is not None:
-                deprecation_message = (
-                    f"You are trying to load the model files of the `variant={variant}`, but no such modeling files are available."
-                    f"The default model files: {model_filenames} will be loaded instead. Make sure to not load from `variant={variant}`"
-                    "if such variant modeling files are not available. Doing so will lead to an error in v0.24.0 as defaulting to non-variant"
-                    "modeling files is deprecated."
-                )
-                deprecate("no variant default", "0.24.0", deprecation_message, standard_warn=False)
+                error_message = f"You are trying to load the model files of the `variant={variant}`, but no such modeling files are available."
+                raise ValueError(error_message)
 
             # remove ignored filenames
             model_filenames = set(model_filenames) - set(ignore_filenames)

src/diffusers/utils/hub_utils.py

@@ -271,8 +271,7 @@ def move_cache(old_cache_dir: Optional[str] = None, new_cache_dir: Optional[str]
 def _add_variant(weights_name: str, variant: Optional[str] = None) -> str:
     if variant is not None:
         splits = weights_name.split(".")
-        split_index = -2 if weights_name.endswith(".index.json") else -1
-        splits = splits[:-split_index] + [variant] + splits[-split_index:]
+        splits = splits[:-1] + [variant] + splits[-1:]
         weights_name = ".".join(splits)
 
     return weights_name
@@ -502,6 +501,19 @@ def _get_checkpoint_shard_files(
     return cached_folder, sharded_metadata
 
 
+def _check_legacy_sharding_variant_format(folder: str = None, filenames: List[str] = None, variant: str = None):
+    if filenames and folder:
+        raise ValueError("Both `filenames` and `folder` cannot be provided.")
+    if not filenames:
+        filenames = []
+        for _, _, files in os.walk(folder):
+            for file in files:
+                filenames.append(os.path.basename(file))
+    transformers_index_format = r"\d{5}-of-\d{5}"
+    variant_file_re = re.compile(rf".*-{transformers_index_format}\.{variant}\.[a-z]+$")
+    return any(variant_file_re.match(f) is not None for f in filenames)
+
+
 class PushToHubMixin:
     """
     A Mixin to push a model, scheduler, or pipeline to the Hugging Face Hub.