Agent skill

unused-code-cleanup

Systematically identify and remove unused imports, variables, and dead code from TypeScript/React projects using --noUnusedLocals and --noUnusedParameters compiler flags

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/phamhung075/4genthub-hooks/tree/main/skills/unused-code-cleanup

SKILL.md

Unused Code Cleanup

Identify and remove unused imports/variables/dead code from TypeScript/React projects.

When to Use

  • TypeScript projects with unused code warnings
  • After major refactoring or feature removal
  • Pre-production cleanup for bundle size optimization
  • Code quality improvement initiatives

Detection

Task Command
Detect npx tsc --noEmit --noUnusedLocals --noUnusedParameters 2>&1 | grep "error TS6133"
Count ... | wc -l
High-impact files ... | sed 's/([0-9]*,[0-9]*).*//' | sort | uniq -c | sort -rn | head -15

Common Patterns

Pattern Cause Impact Difficulty
Unused imports Icon libraries, API types Smaller bundle Easy
Dead feature Feature removed, code remains Reveals subsystems Complex
Unused parameters React Query error callbacks Clean conventions Easy
Debug snapshots Debugging code left in Runtime performance Easy
Unused props Component refactoring Interface clarity Medium
Unused hooks Removed functionality Prevent unnecessary renders Easy

Cleanup Strategy

  1. Prioritize high-impact → Files with 10+ warnings first
  2. Identify patterns → Imports (quick wins), state (dead features), parameters (callbacks), variables (debug)
  3. Verify each file → npm run build && npx tsc --noEmit
  4. Track progress → Start count → Current count

Key Insights

Cascading dependencies: Unused state → unused setters → unused conversion functions → entire dead feature subsystems

Performance:

  • Removing unused getQueryData() improves runtime
  • Smaller bundle from unused import removal
  • Faster TypeScript compilation

Debug archaeology: beforeCache/afterCache variables reveal debugging history (often paired with removed console.log)

Common Mistakes

Mistake Issue Solution
Remove used destructured error might be used later Check all references
Miss dynamic calls String references to functions Search for function name
No build verification Reflection/dynamic imports break Run build after each file
Remove API-required params Breaking callback signature Use _ for unused params

Session Metrics (Example: 2025-11-08)

Metric Value
Warnings 148 → 101 (32% reduction)
Files cleaned 6
Items removed 47
Build time 15.30s

Files:

File Warnings Items
BranchContextDialog.tsx 22 Icons, parsing functions, state
useRealtimeSync.ts 12 Debug snapshot variables
useSubtasks.ts 4 Unused onError parameters
useTasks.ts 2 Unused onError parameters
api-lazy.ts 4 Unused type/API imports
LazySubtaskList/* 5 queryClient, props, parameters

Automation

ESLint

json
{
  "rules": {
    "@typescript-eslint/no-unused-vars": ["error", {
      "argsIgnorePattern": "^_",
      "varsIgnorePattern": "^_"
    }]
  }
}

Pre-commit Hook

bash
#!/bin/bash
unused=$(npx tsc --noEmit --noUnusedLocals --noUnusedParameters 2>&1 | grep "error TS6133" | wc -l)
[ $unused -gt 0 ] && echo "⚠️ $unused unused code warnings"

Quick Reference

Task Command
Detect npx tsc --noEmit --noUnusedLocals --noUnusedParameters
Count ... | grep "error TS6133" | wc -l
High-impact ... | sed 's/([0-9]*,[0-9]*).*//' | sort | uniq -c | sort -rn
Build npm run build
TypeScript npx tsc --noEmit

Supporting Files

  • EXAMPLES.md - 9 patterns with before/after code, session example (148→101), cascading dependencies, performance impact
  • TEMPLATES.md - Detection commands, cleanup workflows, 9 pattern templates, progress tracking
  • VALIDATION.md - Pre/during/post checklists, validation commands, quality checks by pattern, metrics collection

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