[wwww-deeeee]

Summary

Fixes #25: Boolean and string argument with no value is not parsed as true.

Root Cause

When a flag is configured in both opts.boolean and opts.string (e.g. { boolean: ['foo'], string: ['foo'] }), passing --foo without a value sets val = true. In toVal, the opts.string check was evaluated first, which treated val === true as empty string '' via val == null || val === true ? '' : String(val).

Changes

1. src/index.js:
   • In toVal, prioritize checking if val === true when a key is present in both opts.boolean and opts.string, preserving true as the parsed value.
2. test/index.js:
   • Added unit test suite for flags configured as both boolean and string (--foo -> true, --foo --bar -> true, --foo hello -> 'hello', --foo "" -> '').
   • All 88 tests pass (84 existing + 4 new).