Fix cache versioning when BLACK_CACHE_DIR is set (#3937)

CHANGES.md

@@ -24,6 +24,8 @@
 
 <!-- Changes to how Black can be configured -->
 
+- Fix cache versioning logic when `BLACK_CACHE_DIR` is set (#3937)
+
 ### Packaging
 
 <!-- Changes to how Black is packaged, such as dependency requirements -->

src/black/cache.py

@@ -36,8 +36,9 @@ def get_cache_dir() -> Path:
     repeated calls.
     """
     # NOTE: Function mostly exists as a clean way to test getting the cache directory.
-    default_cache_dir = user_cache_dir("black", version=__version__)
+    default_cache_dir = user_cache_dir("black")
     cache_dir = Path(os.environ.get("BLACK_CACHE_DIR", default_cache_dir))
+    cache_dir = cache_dir / __version__
     return cache_dir
 
 

tests/test_black.py

@@ -1963,11 +1963,11 @@ def test_get_cache_dir(
         # If BLACK_CACHE_DIR is not set, use user_cache_dir
         monkeypatch.delenv("BLACK_CACHE_DIR", raising=False)
         with patch_user_cache_dir:
-            assert get_cache_dir() == workspace1
+            assert get_cache_dir().parent == workspace1
 
         # If it is set, use the path provided in the env var.
         monkeypatch.setenv("BLACK_CACHE_DIR", str(workspace2))
-        assert get_cache_dir() == workspace2
+        assert get_cache_dir().parent == workspace2
 
     def test_cache_broken_file(self) -> None:
         mode = DEFAULT_MODE