feat: Tiny linter like flake8 (Supported by Codex)

Author: ftnext

kotoha/first_linter.py

@@ -0,0 +1,63 @@
+import argparse
+import ast
+import importlib
+from collections.abc import Iterable
+from pathlib import Path
+
+
+def _load_rule(rule_spec: str) -> type[ast.NodeVisitor]:
+    """Load a rule class from MODULE:CLASS specification."""
+    module_name, class_name = rule_spec.split(":", 1)
+    module = importlib.import_module(module_name)
+    return getattr(module, class_name)
+
+
+def _run_rules_for_file(
+    filename: str, source: str, rule_classes: list[type[ast.NodeVisitor]]
+) -> list[str]:
+    tree = ast.parse(source, filename=filename)
+    total_violations = []
+    for rule_cls in rule_classes:
+        visitor = rule_cls()
+        visitor.visit(tree)
+        total_violations.extend((filename, *v) for v in visitor.violations)
+    return total_violations
+
+
+def run(
+    files: Iterable[Path], rule_classes: Iterable[type[ast.NodeVisitor]]
+) -> list[str]:
+    rule_classes = list(rule_classes)
+    all_violations = []
+    for file in files:
+        source = file.read_text("utf8")
+        all_violations.extend(_run_rules_for_file(file.name, source, rule_classes))
+    return all_violations
+
+
+def build_parser() -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser(description="Tiny AST linter")
+    parser.add_argument("files", type=Path, nargs="+", help="Python files to lint")
+    parser.add_argument(
+        "--rule",
+        action="append",
+        required=True,
+        metavar="MODULE:CLASS",
+        help="Rule class to load (repeatable)",
+    )
+    return parser
+
+
+def main(argv: list[str] | None = None) -> None:
+    args = build_parser().parse_args(argv)
+
+    rule_classes = [_load_rule(rule_spec) for rule_spec in args.rule]
+    violations = run(args.files, rule_classes)
+
+    for violation in violations:
+        print(f"{violation[0]}:{violation[1]}:{violation[2]}: {violation[3]}")
+    return 1 if violations else 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

kotoha/kotoha_visitor.py

@@ -0,0 +1,14 @@
+import ast
+
+
+class ArgumentListTypeHintChecker(ast.NodeVisitor):
+    def __init__(self):
+        self.violations = []
+
+    def visit_arg(self, node):
+        annotation = node.annotation
+        if annotation.value.id == "list":
+            as_is = f"{node.arg}: {annotation.value.id}[{annotation.slice.id}]"
+            message = f"Fix type hint `{as_is}`"
+            self.violations.append((node.lineno, node.col_offset, message))
+        self.generic_visit(node)