[core] respect local_files_only=True when using sharded checkpoints

src/diffusers/utils/hub_utils.py

@@ -402,15 +402,17 @@ def _get_checkpoint_shard_files(
         allow_patterns = [os.path.join(subfolder, p) for p in allow_patterns]
 
     ignore_patterns = ["*.json", "*.md"]
-    # `model_info` call must guarded with the above condition.
-    model_files_info = model_info(pretrained_model_name_or_path, revision=revision, token=token)
-    for shard_file in original_shard_filenames:
-        shard_file_present = any(shard_file in k.rfilename for k in model_files_info.siblings)
-        if not shard_file_present:
-            raise EnvironmentError(
-                f"{shards_path} does not appear to have a file named {shard_file} which is "
-                "required according to the checkpoint index."
-            )
+
+    # If the repo doesn't have the required shards, error out early even before downloading anything.
+    if not local_files_only:
+        model_files_info = model_info(pretrained_model_name_or_path, revision=revision, token=token)
+        for shard_file in original_shard_filenames:
+            shard_file_present = any(shard_file in k.rfilename for k in model_files_info.siblings)
+            if not shard_file_present:
+                raise EnvironmentError(
+                    f"{shards_path} does not appear to have a file named {shard_file} which is "
+                    "required according to the checkpoint index."
+                )
 
     try:
         # Load from URL
@@ -437,6 +439,11 @@ def _get_checkpoint_shard_files(
         ) from e
 
     cached_filenames = [os.path.join(cached_folder, f) for f in original_shard_filenames]
+    for cached_file in cached_filenames:
+        if not os.path.isfile(cached_file):
+            raise EnvironmentError(
+                f"{cached_folder} does not have a file named {cached_file} which is required according to the checkpoint index."
+            )
 
     return cached_filenames, sharded_metadata
 

tests/models/test_modeling_common.py

@@ -36,12 +36,12 @@
 import torch
 import torch.nn as nn
 from accelerate.utils.modeling import _get_proper_dtype, compute_module_sizes, dtype_byte_size
-from huggingface_hub import ModelCard, delete_repo, snapshot_download
+from huggingface_hub import ModelCard, delete_repo, snapshot_download, try_to_load_from_cache
 from huggingface_hub.utils import is_jinja_available
 from parameterized import parameterized
 from requests.exceptions import HTTPError
 
-from diffusers.models import SD3Transformer2DModel, UNet2DConditionModel
+from diffusers.models import FluxTransformer2DModel, SD3Transformer2DModel, UNet2DConditionModel
 from diffusers.models.attention_processor import (
     AttnProcessor,
     AttnProcessor2_0,
@@ -291,6 +291,54 @@ def test_cached_files_are_used_when_no_internet(self):
             if p1.data.ne(p2.data).sum() > 0:
                 assert False, "Parameters not the same!"
 
+    def test_local_files_only_with_sharded_checkpoint(self):
+        repo_id = "hf-internal-testing/tiny-flux-sharded"
+        error_response = mock.Mock(
+            status_code=500,
+            headers={},
+            raise_for_status=mock.Mock(side_effect=HTTPError),
+            json=mock.Mock(return_value={}),
+        )
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            model = FluxTransformer2DModel.from_pretrained(repo_id, subfolder="transformer", cache_dir=tmpdir)
+
+            with mock.patch("requests.Session.get", return_value=error_response):
+                # Should fail with local_files_only=False (network required)
+                # We would make a network call with model_info
+                with self.assertRaises(OSError):
+                    FluxTransformer2DModel.from_pretrained(
+                        repo_id, subfolder="transformer", cache_dir=tmpdir, local_files_only=False
+                    )
+
+                # Should succeed with local_files_only=True (uses cache)
+                # model_info call skipped
+                local_model = FluxTransformer2DModel.from_pretrained(
+                    repo_id, subfolder="transformer", cache_dir=tmpdir, local_files_only=True
+                )
+
+            assert all(torch.equal(p1, p2) for p1, p2 in zip(model.parameters(), local_model.parameters())), (
+                "Model parameters don't match!"
+            )
+
+            # Remove a shard file
+            cached_shard_file = try_to_load_from_cache(
+                repo_id, filename="transformer/diffusion_pytorch_model-00001-of-00002.safetensors", cache_dir=tmpdir
+            )
+            os.remove(cached_shard_file)
+
+            # Attempting to load from cache should raise an error
+            with self.assertRaises(OSError) as context:
+                FluxTransformer2DModel.from_pretrained(
+                    repo_id, subfolder="transformer", cache_dir=tmpdir, local_files_only=True
+                )
+
+            # Verify error mentions the missing shard
+            error_msg = str(context.exception)
+            assert cached_shard_file in error_msg or "required according to the checkpoint index" in error_msg, (
+                f"Expected error about missing shard, got: {error_msg}"
+            )
+
     @unittest.skip("Flaky behaviour on CI. Re-enable after migrating to new runners")
     @unittest.skipIf(torch_device == "mps", reason="Test not supported for MPS.")
     def test_one_request_upon_cached(self):