Use "hub" directory for cache instead of "diffusers" (#2005)

* Use "hub" directory for cache instead of "diffusers"

* Import cache locations from huggingface_hub

I verified that the constants are available in huggingface_hub version
0.10.0, which is the minimum we require.
Co-authored-by: Lucain Pouget <lucainp@gmail.com>

* make style

* Move cached directories to new location.

* make style

* Apply suggestions by @Wauplin
Co-authored-by: Lucain <lucainp@gmail.com>

* Fix is_file

* Ignore symlinks.

Especially important if we want to ensure that the user may want to invoke the
process again later, if they are keeping multiple envs with different
versions.

* Style

---------
Co-authored-by: Lucain Pouget <lucainp@gmail.com>

src/diffusers/utils/constants.py

@@ -13,11 +13,10 @@
 # limitations under the License.
 import os
 
+from huggingface_hub.constants import HUGGINGFACE_HUB_CACHE, hf_cache_home
 
-hf_cache_home = os.path.expanduser(
-    os.getenv("HF_HOME", os.path.join(os.getenv("XDG_CACHE_HOME", "~/.cache"), "huggingface"))
-)
-default_cache_path = os.path.join(hf_cache_home, "diffusers")
+
+default_cache_path = HUGGINGFACE_HUB_CACHE
 
 
 CONFIG_NAME = "config.json"

src/diffusers/utils/hub_utils.py

@@ -16,6 +16,7 @@
 
 import os
 import sys
+import traceback
 from pathlib import Path
 from typing import Dict, Optional, Union
 from uuid import uuid4
@@ -24,7 +25,7 @@ from huggingface_hub import HfFolder, ModelCard, ModelCardData, whoami
 from huggingface_hub.utils import is_jinja_available
 
 from .. import __version__
-from .constants import HUGGINGFACE_CO_RESOLVE_ENDPOINT
+from .constants import DIFFUSERS_CACHE, HUGGINGFACE_CO_RESOLVE_ENDPOINT
 from .import_utils import (
     ENV_VARS_TRUE_VALUES,
     _flax_version,
@@ -129,3 +130,72 @@ def create_model_card(args, model_name):
 
     card_path = os.path.join(args.output_dir, "README.md")
     model_card.save(card_path)
+
+
+# Old default cache path, potentially to be migrated.
+# This logic was more or less taken from `transformers`, with the following differences:
+# - Diffusers doesn't use custom environment variables to specify the cache path.
+# - There is no need to migrate the cache format, just move the files to the new location.
+hf_cache_home = os.path.expanduser(
+    os.getenv("HF_HOME", os.path.join(os.getenv("XDG_CACHE_HOME", "~/.cache"), "huggingface"))
+)
+old_diffusers_cache = os.path.join(hf_cache_home, "diffusers")
+
+
+def move_cache(old_cache_dir: Optional[str] = None, new_cache_dir: Optional[str] = None) -> None:
+    if new_cache_dir is None:
+        new_cache_dir = DIFFUSERS_CACHE
+    if old_cache_dir is None:
+        old_cache_dir = old_diffusers_cache
+
+    old_cache_dir = Path(old_cache_dir).expanduser()
+    new_cache_dir = Path(new_cache_dir).expanduser()
+    for old_blob_path in old_cache_dir.glob("**/blobs/*"):  #  move file blob by blob
+        if old_blob_path.is_file() and not old_blob_path.is_symlink():
+            new_blob_path = new_cache_dir / old_blob_path.relative_to(old_cache_dir)
+            new_blob_path.parent.mkdir(parents=True, exist_ok=True)
+            os.replace(old_blob_path, new_blob_path)
+            try:
+                os.symlink(new_blob_path, old_blob_path)
+            except OSError:
+                logger.warning(
+                    "Could not create symlink between old cache and new cache. If you use an older version of diffusers again, files will be re-downloaded."
+                )
+    # At this point, old_cache_dir contains symlinks to the new cache (it can still be used).
+
+
+cache_version_file = os.path.join(DIFFUSERS_CACHE, "version_diffusers_cache.txt")
+if not os.path.isfile(cache_version_file):
+    cache_version = 0
+else:
+    with open(cache_version_file) as f:
+        cache_version = int(f.read())
+
+if cache_version < 1:
+    old_cache_is_not_empty = os.path.isdir(old_diffusers_cache) and len(os.listdir(old_diffusers_cache)) > 0
+    if old_cache_is_not_empty:
+        logger.warning(
+            "The cache for model files in Diffusers v0.14.0 has moved to a new location. Moving your "
+            "existing cached models. This is a one-time operation, you can interrupt it or run it "
+            "later by calling `diffusers.utils.hub_utils.move_cache()`."
+        )
+        try:
+            move_cache()
+        except Exception as e:
+            trace = "\n".join(traceback.format_tb(e.__traceback__))
+            logger.error(
+                f"There was a problem when trying to move your cache:\n\n{trace}\n{e.__class__.__name__}: {e}\n\nPlease "
+                "file an issue at https://github.com/huggingface/diffusers/issues/new/choose, copy paste this whole "
+                "message and we will do our best to help."
+            )
+
+if cache_version < 1:
+    try:
+        os.makedirs(DIFFUSERS_CACHE, exist_ok=True)
+        with open(cache_version_file, "w") as f:
+            f.write("1")
+    except Exception:
+        logger.warning(
+            f"There was a problem when trying to write in your cache folder ({DIFFUSERS_CACHE}). Please, ensure "
+            "the directory exists and can be written to."
+        )