Fix #518, provide --enforce-all option to check_added_large_files

The --enforce-all option when provided ensures that all files passed
on the command line are checked against the size limit.  Default
behaviour remains unchanged.

README.md

@@ -26,8 +26,11 @@ Add this to your `.pre-commit-config.yaml`
 #### `check-added-large-files`
 Prevent giant files from being committed.
   - Specify what is "too large" with `args: ['--maxkb=123']` (default=500kB).
+  - Limits checked files to those indicated as staged for addition by git.
   - If `git-lfs` is installed, lfs files will be skipped
     (requires `git-lfs>=2.2.1`)
+  - `--enforce-all` - Check all listed files not just those staged for
+    addition.
 
 #### `check-ast`
 Simply check whether files parse as valid python.

pre_commit_hooks/check_added_large_files.py

@@ -21,11 +21,20 @@ def lfs_files() -> Set[str]:
     return set(json.loads(lfs_ret)['files'])
 
 
-def find_large_added_files(filenames: Sequence[str], maxkb: int) -> int:
+def find_large_added_files(
+        filenames: Sequence[str],
+        maxkb: int,
+        *,
+        enforce_all: bool = False,
+) -> int:
     # Find all added files that are also in the list of files pre-commit tells
     # us about
     retv = 0
-    for filename in (added_files() & set(filenames)) - lfs_files():
+    filenames_filtered = set(filenames) - lfs_files()
+    if not enforce_all:
+        filenames_filtered &= added_files()
+
+    for filename in filenames_filtered:
         kb = int(math.ceil(os.stat(filename).st_size / 1024))
         if kb > maxkb:
             print(f'{filename} ({kb} KB) exceeds {maxkb} KB.')
@@ -40,13 +49,21 @@ def main(argv: Optional[Sequence[str]] = None) -> int:
         'filenames', nargs='*',
         help='Filenames pre-commit believes are changed.',
     )
+    parser.add_argument(
+        '--enforce-all', action='store_true',
+        help='Enforce all files are checked, not just staged files.',
+    )
     parser.add_argument(
         '--maxkb', type=int, default=500,
         help='Maxmimum allowable KB for added files',
     )
-
     args = parser.parse_args(argv)
-    return find_large_added_files(args.filenames, args.maxkb)
+
+    return find_large_added_files(
+        args.filenames,
+        args.maxkb,
+        enforce_all=args.enforce_all,
+    )
 
 
 if __name__ == '__main__':

tests/check_added_large_files_test.py

@@ -40,6 +40,17 @@ def test_add_something_giant(temp_git_dir):
         assert find_large_added_files(['f.py'], 10) == 0
 
 
+def test_enforce_all(temp_git_dir):
+    with temp_git_dir.as_cwd():
+        temp_git_dir.join('f.py').write('a' * 10000)
+
+        # Should fail, when not staged with enforce_all
+        assert find_large_added_files(['f.py'], 0, enforce_all=True) == 1
+
+        # Should pass, when not staged without enforce_all
+        assert find_large_added_files(['f.py'], 0, enforce_all=False) == 0
+
+
 def test_added_file_not_in_pre_commits_list(temp_git_dir):
     with temp_git_dir.as_cwd():
         temp_git_dir.join('f.py').write("print('hello world')")
@@ -97,3 +108,15 @@ def test_moves_with_gitlfs(temp_git_dir, monkeypatch):  # pragma: no cover
         # Now move it and make sure the hook still succeeds
         cmd_output('git', 'mv', 'a.bin', 'b.bin')
         assert main(('--maxkb', '9', 'b.bin')) == 0
+
+
+@xfailif_no_gitlfs
+def test_enforce_allows_gitlfs(temp_git_dir, monkeypatch):  # pragma: no cover
+    with temp_git_dir.as_cwd():
+        monkeypatch.setenv('HOME', str(temp_git_dir))
+        cmd_output('git', 'lfs', 'install')
+        temp_git_dir.join('f.py').write('a' * 10000)
+        cmd_output('git', 'lfs', 'track', 'f.py')
+        cmd_output('git', 'add', '--', '.')
+        # With --enforce-all large files on git lfs should succeed
+        assert main(('--enforce-all', '--maxkb', '9', 'f.py')) == 0