# TypeScript Strict Mode Configuration

## FE-TYPE-014: Add strict TypeScript mode

This document describes the TypeScript strict mode configuration for the Veza frontend application.

## Current Configuration

All TypeScript configuration files (`tsconfig.json`, `tsconfig.app.json`, `tsconfig.node.json`) have been updated with comprehensive strict mode options:

### Enabled Strict Options

- ✅ `strict: true` - Enables all strict type checking options
- ✅ `noImplicitAny: true` - Prevents implicit `any` types
- ✅ `strictNullChecks: true` - Ensures null/undefined safety
- ✅ `strictFunctionTypes: true` - Stricter checking of function types
- ✅ `strictBindCallApply: true` - Stricter checking of bind/call/apply
- ✅ `strictPropertyInitialization: true` - Ensures class properties are initialized
- ✅ `noImplicitThis: true` - Prevents implicit `this` with `any` type
- ✅ `alwaysStrict: true` - Parses in strict mode and emits "use strict"
- ✅ `noUnusedLocals: true` - Reports errors on unused local variables
- ✅ `noUnusedParameters: true` - Reports errors on unused parameters
- ✅ `noImplicitReturns: true` - Ensures all code paths return a value
- ✅ `noFallthroughCasesInSwitch: true` - Prevents fallthrough in switch statements
- ✅ `noImplicitOverride: true` - Requires explicit `override` keyword

### Deferred Options

- ⏳ `noUncheckedIndexedAccess: true` - Currently commented out
  - **Reason**: Would require fixing 200+ array/object access checks
  - **Plan**: Enable progressively as code is refactored
  - **Impact**: Makes array/object access return `T | undefined` instead of `T`

## Benefits

1. **Type Safety**: Catches type errors at compile time
2. **Null Safety**: Prevents null/undefined runtime errors
3. **Code Quality**: Enforces best practices and prevents common mistakes
4. **IDE Support**: Better autocomplete and error detection
5. **Refactoring**: Safer code changes with type checking

## Migration Notes

When enabling `noUncheckedIndexedAccess` in the future:

1. Add null checks for array access: `arr[i]` → `arr[i] ?? defaultValue`
2. Add null checks for object access: `obj[key]` → `obj[key] ?? defaultValue`
3. Use optional chaining where appropriate: `obj?.prop`
4. Use nullish coalescing: `value ?? defaultValue`

## Validation

Run type checking:
```bash
npm run typecheck
```

All strict mode options are validated and working correctly.

