138 lines
4.0 KiB
Python
138 lines
4.0 KiB
Python
"""
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Append-only discussion checker.
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Validates that staged changes to discussion Markdown files only modify YAML
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front matter; the body must remain append-only (no deletions or edits).
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"""
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from __future__ import annotations
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import argparse
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import re
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import subprocess
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import sys
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from pathlib import Path
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from typing import Tuple
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DIFF_HUNK_RE = re.compile(r"^@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@")
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def _run_git_show(ref: str, path: Path) -> str | None:
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"""Return file contents for ref:path, or None if unavailable."""
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result = subprocess.run(
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["git", "show", f"{ref}:{path.as_posix()}"],
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capture_output=True,
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text=True,
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)
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if result.returncode != 0:
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return None
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return result.stdout
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def _find_front_matter_end(text: str | None) -> int:
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"""Return 1-based line number of closing --- in YAML front matter."""
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if not text:
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return 0
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lines = text.splitlines()
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if not lines or lines[0].strip() != "---":
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return 0
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for idx, line in enumerate(lines[1:], start=2):
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if line.strip() == "---":
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return idx
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return len(lines)
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def _get_staged_diff(path: Path) -> str:
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result = subprocess.run(
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["git", "diff", "--cached", "--unified=0", "--", path.as_posix()],
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capture_output=True,
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text=True,
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check=False,
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)
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# git diff exits 0 regardless of diff presence
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return result.stdout
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def _is_allowed(diff_text: str, header_end: int) -> Tuple[bool, str]:
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"""
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Return (allowed, offending_line) for staged diff.
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header_end is the line number of the closing front matter delimiter in
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the previous version (0 if no front matter detected).
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"""
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current_old_line = None
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for line in diff_text.splitlines():
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if line.startswith("diff --git") or line.startswith("index "):
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continue
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if line.startswith("--- ") or line.startswith("+++ "):
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continue
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if line.startswith("\\"):
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continue
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if line.startswith("@@"):
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match = DIFF_HUNK_RE.match(line)
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if match:
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current_old_line = int(match.group(1))
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else:
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current_old_line = None
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continue
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if current_old_line is None:
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continue
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prefix = line[:1]
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if prefix == "-":
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# header_end == 0 means no header detected => forbid deletions
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if header_end == 0 or current_old_line > header_end:
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return False, line
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current_old_line += 1
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elif prefix == " ":
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current_old_line += 1
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elif prefix == "+":
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# additions do not advance old line counter
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pass
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return True, ""
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def check_append_only(path: Path) -> Tuple[bool, str]:
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diff_text = _get_staged_diff(path)
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if not diff_text.strip():
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return True, ""
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old_content = _run_git_show("HEAD", path)
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header_end = _find_front_matter_end(old_content)
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allowed, offending = _is_allowed(diff_text, header_end)
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return allowed, offending
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def main(argv: list[str] | None = None) -> int:
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parser = argparse.ArgumentParser(
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description="Ensure discussion files are append-only outside YAML header."
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)
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parser.add_argument("path", help="Discussion file path (relative or absolute)")
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args = parser.parse_args(argv)
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raw_path = Path(args.path)
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path = raw_path
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cwd = Path.cwd().resolve()
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if raw_path.is_absolute():
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try:
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path = raw_path.resolve().relative_to(cwd)
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except ValueError:
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sys.stderr.write(
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f"[pre-commit] Error: {raw_path} is outside the repository root\n"
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)
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return 1
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allowed, offending_line = check_append_only(path)
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if allowed:
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return 0
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sys.stderr.write(
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"[pre-commit] Error: Discussion files must be append-only; "
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f"modification detected outside YAML header:\n {offending_line}\n"
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)
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return 1
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if __name__ == "__main__":
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raise SystemExit(main())
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