Rust: add linting pre-commit hook

.pre-commit-config.yaml

@@ -76,3 +76,10 @@ repos:
         language: system
         entry: bazel run //rust/codegen -- --quiet
         pass_filenames: false
+
+      - id: rust-lint
+        name: Run fmt and clippy on Rust code
+        files: ^rust/extractor/(.*rs|Cargo.toml)$
+        language: system
+        entry: python3 rust/lint.py
+        pass_filenames: false

rust/lint.py

@@ -0,0 +1,16 @@
+#!/bin/env python3
+
+import subprocess
+import pathlib
+import shutil
+import sys
+
+extractor_dir = pathlib.Path(__file__).resolve().parent / "extractor"
+
+cargo = shutil.which("cargo")
+assert cargo, "no cargo binary found on `PATH`"
+
+fmt = subprocess.run([cargo, "fmt", "--quiet"], cwd=extractor_dir)
+clippy = subprocess.run([cargo, "clippy", "--fix", "--allow-dirty", "--allow-staged", "--quiet"],
+                        cwd=extractor_dir)
+sys.exit(fmt.returncode or clippy.returncode)