gemini-nexus/.agents/skills/lodash-es-runtime-guards/SKILL.md

lodash-es-runtime-guards

Replace runtime typeof checks and ad-hoc empty-string checks with lodash-es predicates.

When to Use

• You see runtime checks like typeof value === 'string'.
• You see object guards like value && typeof value === 'object'.
• You see emptiness checks like value.trim() !== '' or value.trim() === ''.
• You want consistent guard style across app, server, IPC, and tests.

Do Not Replace

• Type-level typeof (TypeScript only), for example:
  • ReturnType<typeof fn>
  • keyof typeof CONST_MAP
  • z.infer<typeof Schema>

These are compile-time types and must remain as-is.

Guard Mapping

• typeof x === 'string' -> isString(x)
• typeof x !== 'string' -> !isString(x)
• typeof x === 'number' -> isNumber(x)
• typeof x === 'boolean' -> isBoolean(x)
• typeof x === 'function' -> isFunction(x)
• typeof x === 'undefined' -> isUndefined(x)
• x && typeof x === 'object' -> isObjectLike(x)
• typeof x === 'object' && x !== null -> isObjectLike(x)
• typeof x === 'object' && !Array.isArray(x) -> isObjectLike(x) && !isArray(x)

String Emptiness Pattern

• Prefer:
  • isEmpty(value.trim())
• Instead of:
  • value.trim() === ''
  • value.trim() !== ''
  • value.trim().length === 0

Import Style

• Use named imports from lodash-es:

import { isString, isNumber, isObjectLike, isEmpty } from 'lodash-es';

• Do not use full-package imports.
• Reuse existing imports in file; avoid duplicate imports.

Refactor Checklist

1. Replace runtime checks first, preserving behavior.
2. Keep array/object branching semantics unchanged.
3. Re-scan:

rg -n "typeof\s+[^\n]+(?:===|!==)\s*'" src

4. Confirm only type-level typeof remains:

rg -n "\btypeof\b" src

5. Run verification:

npm run type-check