🔧 Lessons Learned - TypeScript Error Fixes

Issues Detected and Resolved

Error 1: Unused Import

src/utils/logger.ts(2,16): error TS6133: 'dirname' is declared but its value is never read.

Cause: dirname import not used in code

Solution: Removed dirname import from line 2

Modified file: src/utils/logger.ts

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Error 2: Missing Export

src/utils/logger.ts(3,25): error TS2305: Module '"../types/config.js"' has no exported member 'LogEntry'.

Cause: LogEntry was defined in tools.ts but logger.ts tried to import it from config.ts

Solution:

1. Added LogEntry interface to src/types/config.ts
2. Removed duplicate LogEntry from src/types/tools.ts

Modified files:

• src/types/config.ts - Added LogEntry
• src/types/tools.ts - Removed duplicate

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Error 3: Implicit ‘any’ Type

src/utils/logger.ts(31,11): error TS7053: Element implicitly has an 'any' type because expression of type 'any' can't be used to index type '{ DEBUG: number; INFO: number; WARN: number; ERROR: number; }'.

Cause: The logLevels property had no explicit type, causing indexing errors

Solution: Added explicit type to logLevels:

private logLevels: Record<string, number> = { DEBUG: 0, INFO: 1, WARN: 2, ERROR: 3 };

And improved level comparison logic:

const entryLevelValue = this.logLevels[entryLevel];
const configLevelValue = this.logLevels[this.level];

if (entryLevelValue < configLevelValue) {
  return;
}

Modified file: src/utils/logger.ts

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Modified Files

1. src/types/config.ts
   • ✅ Added LogEntry interface
   • ✅ Maintained all other types
2. src/types/tools.ts
   • ✅ Removed duplicate LogEntry
   • ✅ Kept all other types
3. src/utils/logger.ts
   • ✅ Removed unused dirname import
   • ✅ Correct import of LogEntry from config.ts
   • ✅ Added Record<string, number> type for logLevels
   • ✅ Improved log level comparison logic

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Validation

To validate all errors are fixed:

cd packages/dev-tools

# 1. Clean old build
npm run clean

# 2. Check types
npm run type-check

# 3. Compile
npm run build

# 4. Run tests
npm test

Expected result: No TypeScript errors, successful compilation

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Prevention

These errors were caused by:

1. Initial type organization between config.ts and tools.ts
2. Uncleaned imports
3. Implicit types with TypeScript strict mode

To avoid in the future:

• Always verify compilation after each file addition
• Use npm run type-check regularly
• Organize types logically from the start
• Enable auto-import cleanup in editor

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Status

✅ All TypeScript errors are now fixed

The package should now compile without errors. You can proceed with:

npm run build

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Lessons learned documented - October 19, 2025