add pre-commit hazmat

pre_commit/commands/hazmat.py

@@ -0,0 +1,95 @@
+from __future__ import annotations
+
+import argparse
+import subprocess
+from collections.abc import Sequence
+
+from pre_commit.parse_shebang import normalize_cmd
+
+
+def add_parsers(parser: argparse.ArgumentParser) -> None:
+    subparsers = parser.add_subparsers(dest='tool')
+
+    cd_parser = subparsers.add_parser(
+        'cd', help='cd to a subdir and run the command',
+    )
+    cd_parser.add_argument('subdir')
+    cd_parser.add_argument('cmd', nargs=argparse.REMAINDER)
+
+    ignore_exit_code_parser = subparsers.add_parser(
+        'ignore-exit-code', help='run the command but ignore the exit code',
+    )
+    ignore_exit_code_parser.add_argument('cmd', nargs=argparse.REMAINDER)
+
+    n1_parser = subparsers.add_parser(
+        'n1', help='run the command once per filename',
+    )
+    n1_parser.add_argument('cmd', nargs=argparse.REMAINDER)
+
+
+def _cmd_filenames(cmd: tuple[str, ...]) -> tuple[
+    tuple[str, ...],
+    tuple[str, ...],
+]:
+    for idx, val in enumerate(reversed(cmd)):
+        if val == '--':
+            split = len(cmd) - idx
+            break
+    else:
+        raise SystemExit('hazmat entry must end with `--`')
+
+    return cmd[:split - 1], cmd[split:]
+
+
+def cd(subdir: str, cmd: tuple[str, ...]) -> int:
+    cmd, filenames = _cmd_filenames(cmd)
+
+    prefix = f'{subdir}/'
+    new_filenames = []
+    for filename in filenames:
+        if not filename.startswith(prefix):
+            raise SystemExit(f'unexpected file without {prefix=}: {filename}')
+        else:
+            new_filenames.append(filename.removeprefix(prefix))
+
+    cmd = normalize_cmd(cmd)
+    return subprocess.call((*cmd, *new_filenames), cwd=subdir)
+
+
+def ignore_exit_code(cmd: tuple[str, ...]) -> int:
+    cmd = normalize_cmd(cmd)
+    subprocess.call(cmd)
+    return 0
+
+
+def n1(cmd: tuple[str, ...]) -> int:
+    cmd, filenames = _cmd_filenames(cmd)
+    cmd = normalize_cmd(cmd)
+    ret = 0
+    for filename in filenames:
+        ret |= subprocess.call((*cmd, filename))
+    return ret
+
+
+def impl(args: argparse.Namespace) -> int:
+    args.cmd = tuple(args.cmd)
+    if args.tool == 'cd':
+        return cd(args.subdir, args.cmd)
+    elif args.tool == 'ignore-exit-code':
+        return ignore_exit_code(args.cmd)
+    elif args.tool == 'n1':
+        return n1(args.cmd)
+    else:
+        raise NotImplementedError(f'unexpected tool: {args.tool}')
+
+
+def main(argv: Sequence[str] | None = None) -> int:
+    parser = argparse.ArgumentParser()
+    add_parsers(parser)
+    args = parser.parse_args(argv)
+
+    return impl(args)
+
+
+if __name__ == '__main__':
+    raise SystemExit(main())

pre_commit/lang_base.py

@@ -5,6 +5,7 @@ import os
 import random
 import re
 import shlex
+import sys
 from collections.abc import Generator
 from collections.abc import Sequence
 from typing import Any
@@ -171,7 +172,10 @@ def run_xargs(
 
 
 def hook_cmd(entry: str, args: Sequence[str]) -> tuple[str, ...]:
-    return (*shlex.split(entry), *args)
+    cmd = shlex.split(entry)
+    if cmd[:2] == ['pre-commit', 'hazmat']:
+        cmd = [sys.executable, '-m', 'pre_commit.commands.hazmat', *cmd[2:]]
+    return (*cmd, *args)
 
 
 def basic_run_hook(

pre_commit/main.py

@@ -10,6 +10,7 @@ import pre_commit.constants as C
 from pre_commit import clientlib
 from pre_commit import git
 from pre_commit.color import add_color_option
+from pre_commit.commands import hazmat
 from pre_commit.commands.autoupdate import autoupdate
 from pre_commit.commands.clean import clean
 from pre_commit.commands.gc import gc
@@ -41,7 +42,7 @@ os.environ.pop('__PYVENV_LAUNCHER__', None)
 os.environ.pop('PYTHONEXECUTABLE', None)
 
 COMMANDS_NO_GIT = {
-    'clean', 'gc', 'init-templatedir', 'sample-config',
+    'clean', 'gc', 'hazmat', 'init-templatedir', 'sample-config',
     'validate-config', 'validate-manifest',
 }
 
@@ -245,6 +246,11 @@ def main(argv: Sequence[str] | None = None) -> int:
 
     _add_cmd('gc', help='Clean unused cached repos.')
 
+    hazmat_parser = _add_cmd(
+        'hazmat', help='Composable tools for rare use in hook `entry`.',
+    )
+    hazmat.add_parsers(hazmat_parser)
+
     init_templatedir_parser = _add_cmd(
         'init-templatedir',
         help=(
@@ -389,6 +395,8 @@ def main(argv: Sequence[str] | None = None) -> int:
             return clean(store)
         elif args.command == 'gc':
             return gc(store)
+        elif args.command == 'hazmat':
+            return hazmat.impl(args)
         elif args.command == 'hook-impl':
             return hook_impl(
                 store,