Elaborate on Python support policy (#2819)

[etc/vim.git] / src / black / cache.py

diff --git a/src/black/cache.py b/src/black/cache.py
index 3f165de2ed60bf2563cee4e662baeb36c3553a40..552c248d2ad0644f4855df562b9265ad6b649dd6 100644 (file)
--- a/src/black/cache.py
+++ b/src/black/cache.py
@@ -20,7 +20,23 @@ CacheInfo = Tuple[Timestamp, FileSize]
 Cache = Dict[str, CacheInfo]
 
 
-CACHE_DIR = Path(user_cache_dir("black", version=__version__))
+def get_cache_dir() -> Path:
+    """Get the cache directory used by black.
+
+    Users can customize this directory on all systems using `BLACK_CACHE_DIR`
+    environment variable. By default, the cache directory is the user cache directory
+    under the black application.
+
+    This result is immediately set to a constant `black.cache.CACHE_DIR` as to avoid
+    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__)
+    cache_dir = Path(os.environ.get("BLACK_CACHE_DIR", default_cache_dir))
+    return cache_dir
+
+
+CACHE_DIR = get_cache_dir()
 
 
 def read_cache(mode: Mode) -> Cache:
@@ -35,7 +51,7 @@ def read_cache(mode: Mode) -> Cache:
     with cache_file.open("rb") as fobj:
         try:
             cache: Cache = pickle.load(fobj)
-        except (pickle.UnpicklingError, ValueError):
+        except (pickle.UnpicklingError, ValueError, IndexError):
             return {}
 
     return cache