CLI Application Code Review Patterns

Stack-specific rules loaded by dh:code-reviewer when CLI entrypoints are detected (argparse, click, typer, commander.js, or similar argument parsing libraries).

Exit Codes

• Exit code 0 must be returned only on success — any error condition must produce a non-zero exit code
• Returning exit code 0 after printing an error message is a blocking finding — tools in pipelines cannot detect the failure
• Common conventions: 1 for general errors, 2 for usage/argument errors, 3+ for application-specific codes documented in --help
• sys.exit(1) or process.exit(1) must be called on fatal errors, not just printing to stderr

# WRONG: exits 0 even on error
def main():
    try:
        run()
    except Exception as e:
        print(f"Error: {e}", file=sys.stderr)
    # implicit exit 0