Refresh and enforce license header check

.pre-commit-config.yaml

@@ -35,6 +35,18 @@ repos:
       - id: validate-pyproject
         stages: [pre-commit, manual]
 
+  - repo: local
+    hooks:
+      # Checks every file NOTICE.yml covers, not only the changed ones; add headers with tools/update_license_headers.py
+      - id: license-headers
+        name: license headers (NOTICE.yml)
+        entry: python tools/check_license_headers.py
+        language: python
+        additional_dependencies: [pyyaml]
+        pass_filenames: false
+        always_run: true
+        stages: [pre-commit, manual]
+
   - repo: https://github.com/astral-sh/ruff-pre-commit
     rev: v0.15.6
     hooks:

tools/check_license_headers.py

@@ -0,0 +1,50 @@
+#
+# DeepLabCut Toolbox (deeplabcut.org)
+# © A. & M.W. Mathis Labs
+# https://github.com/DeepLabCut/DeepLabCut
+#
+# Please see AUTHORS for contributors.
+# https://github.com/DeepLabCut/DeepLabCut/blob/master/AUTHORS
+#
+# Licensed under GNU Lesser General Public License v3.0
+#
+
+"""Check that every file NOTICE.yml covers starts with its header.
+
+Reads only; use update_license_headers.py for writing.
+"""
+
+import sys
+from itertools import takewhile
+from pathlib import Path
+
+from update_license_headers import load_config, walk_directory
+
+
+def leading_comment(path: Path) -> list[str]:
+    """Return the file's first comment block, with comment markers and one following space removed."""
+    lines = path.read_text(encoding="utf-8").splitlines()
+    return [line.lstrip("#").removeprefix(" ").rstrip() for line in takewhile(lambda line: line.startswith("#"), lines)]
+
+
+def has_header(path: Path, header: list[str]) -> bool:
+    """Return whether the header lines appear, in order and contiguous, in the file's first comment block."""
+    comment = leading_comment(path)
+    return any(comment[start : start + len(header)] == header for start in range(len(comment) - len(header) + 1))
+
+
+def main(input_file: str = "NOTICE.yml") -> int:
+    """Print each file missing its header and return 1 if there is any, else 0."""
+    missing = []
+    for entry in load_config(input_file):
+        header = [line.rstrip() for line in entry["header"].splitlines()]
+        missing += [name for name in walk_directory(entry) if not has_header(Path(name), header)]
+
+    for name in sorted(missing):
+        print(f"{name}: missing or outdated license header (see {input_file})")
+
+    return 1 if missing else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())