Add Python formatting with Ruff

.github/workflows/lint.yml

@@ -27,6 +27,9 @@ jobs:
       - name: Install project deps with pnpm
         run: |
           pnpm i
+      - name: Install Ruff
+        run: |
+          pip install ruff
       - name: Lint
         run: |
           python3 ./tools/cross/format.py --check

tools/cross/format.py

@@ -3,6 +3,7 @@
 import logging
 import os
 import re
+import shutil
 import subprocess
 from argparse import ArgumentParser, Namespace
 from typing import List, Optional, Tuple, Callable
@@ -11,6 +12,7 @@
 
 CLANG_FORMAT = os.environ.get("CLANG_FORMAT", "clang-format")
 PRETTIER = os.environ.get("PRETTIER", "node_modules/.bin/prettier")
+RUFF = os.environ.get("RUFF", "ruff")
 
 
 def parse_args() -> Namespace:
@@ -78,7 +80,7 @@ def filter_files_by_exts(
     return [
         file
         for file in files
-        if file.startswith(dir_path + "/") and file.endswith(exts)
+        if (dir_path == "." or file.startswith(dir_path + "/")) and file.endswith(exts)
     ]
 
 
@@ -102,6 +104,26 @@ def prettier(files: List[str], check: bool = False) -> bool:
     return result.returncode == 0
 
 
+def ruff(files: List[str], check: bool = False) -> bool:
+    if files and not shutil.which(RUFF):
+        msg = "Cannot find ruff, will not format Python"
+        if check:
+            # In ci, fail.
+            logging.error(msg)
+            return False
+        else:
+            # In a local checkout, let it go. If the user wants Python
+            # formatting they can install ruff and run again.
+            logging.warning(msg)
+            return True
+        return not check
+    cmd = [RUFF, "format"]
+    if check:
+        cmd.append("--check")
+    result = subprocess.run(cmd + files)
+    return result.returncode == 0
+
+
 def git_get_modified_files(
     target: str, source: Optional[str], staged: bool
 ) -> List[str]:
@@ -147,6 +169,7 @@ class FormatConfig:
         formatter=prettier,
     ),
     FormatConfig(directory="src", extensions=(".json",), formatter=prettier),
+    FormatConfig(directory=".", extensions=(".py",), formatter=ruff),
     # TODO: lint bazel files
 ]