Fix json WindowsPath crash (#8662)

* Add check for WindowsPath in to_json_string

On Windows, os.path.join returns a WindowsPath. to_json_string does not convert this from a WindowsPath to a string. Added check for WindowsPath to to_json_saveable.

* Remove extraneous convert to string in test_check_path_types (tests/others/test_config.py)

* Fix style issues in tests/others/test_config.py

* Add unit test to test_config.py to verify that PosixPath and WindowsPath (depending on system) both work when converted to JSON

* Remove distinction between PosixPath and WindowsPath in ConfigMixIn.to_json_string(). Conditional now tests for Path, and uses Path.as_posix() to convert to string.

---------
Co-authored-by: Vincent Dovydaitis <vincedovy@gmail.com>
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

src/diffusers/configuration_utils.py

@@ -23,7 +23,7 @@ import json
 import os
 import re
 from collections import OrderedDict
-from pathlib import PosixPath
+from pathlib import Path
 from typing import Any, Dict, Tuple, Union
 
 import numpy as np
@@ -587,8 +587,8 @@ class ConfigMixin:
         def to_json_saveable(value):
             if isinstance(value, np.ndarray):
                 value = value.tolist()
-            elif isinstance(value, PosixPath):
-                value = str(value)
+            elif isinstance(value, Path):
+                value = value.as_posix()
             return value
 
         config_dict = {k: to_json_saveable(v) for k, v in config_dict.items()}

tests/others/test_config.py

@@ -13,8 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
 import tempfile
 import unittest
+from pathlib import Path
 
 from diffusers import (
     DDIMScheduler,
@@ -91,6 +93,14 @@ class SampleObject4(ConfigMixin):
         pass
 
 
+class SampleObjectPaths(ConfigMixin):
+    config_name = "config.json"
+
+    @register_to_config
+    def __init__(self, test_file_1=Path("foo/bar"), test_file_2=Path("foo bar\\bar")):
+        pass
+
+
 class ConfigTester(unittest.TestCase):
     def test_load_not_from_mixin(self):
         with self.assertRaises(ValueError):
@@ -286,3 +296,11 @@ class ConfigTester(unittest.TestCase):
 
         # Nevertheless "e" should still be correctly loaded to [1, 3] from SampleObject2 instead of defaulting to [1, 5]
         assert new_config_2.config.e == [1, 3]
+
+    def test_check_path_types(self):
+        # Verify that we get a string returned from a WindowsPath or PosixPath (depending on system)
+        config = SampleObjectPaths()
+        json_string = config.to_json_string()
+        result = json.loads(json_string)
+        assert result["test_file_1"] == config.config.test_file_1.as_posix()
+        assert result["test_file_2"] == config.config.test_file_2.as_posix()