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[etc/vim.git] / src / black / cache.py
1 """Caching of formatted files with feature-based invalidation."""
2
3 import os
4 import pickle
5 from pathlib import Path
6 import tempfile
7 from typing import Dict, Iterable, Set, Tuple
8
9 from platformdirs import user_cache_dir
10
11 from black.mode import Mode
12
13 from _black_version import version as __version__
14
15
16 # types
17 Timestamp = float
18 FileSize = int
19 CacheInfo = Tuple[Timestamp, FileSize]
20 Cache = Dict[str, CacheInfo]
21
22
23 CACHE_DIR = Path(user_cache_dir("black", version=__version__))
24
25
26 def read_cache(mode: Mode) -> Cache:
27     """Read the cache if it exists and is well formed.
28
29     If it is not well formed, the call to write_cache later should resolve the issue.
30     """
31     cache_file = get_cache_file(mode)
32     if not cache_file.exists():
33         return {}
34
35     with cache_file.open("rb") as fobj:
36         try:
37             cache: Cache = pickle.load(fobj)
38         except (pickle.UnpicklingError, ValueError, IndexError):
39             return {}
40
41     return cache
42
43
44 def get_cache_file(mode: Mode) -> Path:
45     return CACHE_DIR / f"cache.{mode.get_cache_key()}.pickle"
46
47
48 def get_cache_info(path: Path) -> CacheInfo:
49     """Return the information used to check if a file is already formatted or not."""
50     stat = path.stat()
51     return stat.st_mtime, stat.st_size
52
53
54 def filter_cached(cache: Cache, sources: Iterable[Path]) -> Tuple[Set[Path], Set[Path]]:
55     """Split an iterable of paths in `sources` into two sets.
56
57     The first contains paths of files that modified on disk or are not in the
58     cache. The other contains paths to non-modified files.
59     """
60     todo, done = set(), set()
61     for src in sources:
62         res_src = src.resolve()
63         if cache.get(str(res_src)) != get_cache_info(res_src):
64             todo.add(src)
65         else:
66             done.add(src)
67     return todo, done
68
69
70 def write_cache(cache: Cache, sources: Iterable[Path], mode: Mode) -> None:
71     """Update the cache file."""
72     cache_file = get_cache_file(mode)
73     try:
74         CACHE_DIR.mkdir(parents=True, exist_ok=True)
75         new_cache = {
76             **cache,
77             **{str(src.resolve()): get_cache_info(src) for src in sources},
78         }
79         with tempfile.NamedTemporaryFile(dir=str(cache_file.parent), delete=False) as f:
80             pickle.dump(new_cache, f, protocol=4)
81         os.replace(f.name, cache_file)
82     except OSError:
83         pass