Code Review

Use this skill when reviewing code changes, whether your own or proposed by others.

1. Pre-Review Checklist

Before diving into the code, verify:

• All tests pass (npm test)
• No lint errors (npm run lint)
• No type errors (npm run type-check)
• Dependency rules respected (npm run depcruise:verify)

2. Architecture Review

Boundary Violations

Verify imports respect the Modular Monolith structure:

Example: Catching a Boundary Violation

Problem:

// src/ui/containers/blog/hooks/useBlog.ts
import { BlogPost } from 'server/modules/blog/blog.entity'; // ❌ WRONG

Fix:

// src/ui/containers/blog/hooks/useBlog.ts
import { BlogPost } from 'shared/types/blog'; // ✅ CORRECT

Feature Placement

New features should follow the vertical slice pattern:

• Server: src/server/modules/<feature>/
• UI: src/ui/containers/<feature>/
• Shared Types: src/shared/types/<feature>.ts

3. SOLID Principles Check

Single Responsibility

Each module/component should have one reason to change.

Red Flag: A service that handles both data fetching AND formatting.

Example - Before:

class BlogService {
  async getPost(id: string) {
    /* fetch */
  }
  formatForDisplay(post: BlogPost) {
    /* format */
  } // ❌ Wrong place
}

Example - After:

class BlogService {
  async getPost(id: string) {
    /* fetch only */
  }
}
// Formatting belongs in the UI layer

Open/Closed

Code should be open for extension, closed for modification.

Red Flag: Adding if statements for new types instead of using polymorphism.

Dependency Inversion

Depend on abstractions, not concretions.

This project pattern: Services use interfaces and tokens for injection.

// ✅ GOOD - Depends on interface
constructor(@Inject(TOKENS.BlogService) private readonly service: IBlogService)

// ❌ BAD - Depends on concrete class
constructor(private readonly service: BlogService)

4. React Patterns Check

Component Structure

Example: Reviewing a Hook

Red Flags to Check:

// ❌ Manual auth header (handled by AuthInterceptor)
const { data } = useQuery({
  queryFn: () =>
    axios.get('/api/blog', {
      headers: { Authorization: `Bearer ${token}` }, // ❌ REMOVE THIS
    }),
});

// ✅ Correct - Let interceptor handle auth
const { data } = useQuery({
  queryFn: () => axios.get('/api/blog'),
});

Loading/Error States

All data fetching should use QueryState component:

// ✅ GOOD
<QueryState query={query} empty={<EmptyState />}>
  {(data) => <DataDisplay data={data} />}
</QueryState>

// ❌ BAD - Manual handling without consistency
{isLoading ? <Spinner /> : error ? <Error /> : <DataDisplay />}

5. NestJS Patterns Check

Controller Review

Example: Reviewing a Controller

// ✅ GOOD
@ApiTags('Blog')
@Controller('api/blog')
export class BlogController {
  @Get(':id')
  @ApiOperation({ summary: 'Get blog post by ID' })
  @ApiResponse({ status: 200, description: 'Post found' })
  @ApiResponse({ status: 404, description: 'Post not found' })
  findOne(@Param('id') id: string) {
    /* ... */
  }
}

// ❌ MISSING - No Swagger decorators
@Controller('blog') // ❌ Missing /api prefix
export class BlogController {
  @Get(':id')
  findOne(@Param('id') id: string) {
    /* ... */
  }
}

Service Review

6. Security Review

Critical Checks

Example: Spotting Missing Validation

Problem:

@Post()
create(@Body() body: any) { // ❌ No validation
  return this.service.create(body);
}

Fix:

@Post()
create(@Body() createDto: CreateBlogDto) { // ✅ Validated DTO
  return this.service.create(createDto);
}

7. Performance Review

Database Queries

Frontend Performance

8. Testing Review

Coverage Requirements

This project requires 100% coverage. Verify:

• All branches covered (if/else, ternary, switch)
• Error paths tested
• Edge cases handled (empty arrays, null values)

Test Quality

Example: Reviewing a Test

Red Flag - Testing Implementation:

// ❌ Testing implementation detail
expect(mockService.findAll).toHaveBeenCalledTimes(1);

Better - Testing Behavior:

// ✅ Testing user-visible behavior
expect(screen.getByText('Blog Post Title')).toBeInTheDocument();

9. Documentation Review

When code changes, check if docs need updates:

• JSDoc on public methods
• Swagger decorators on endpoints
• ADR needed for architectural decisions
• Component doc in architecture/components/ if complex

10. Review Checklist Summary

□ Tests pass
□ Lint passes
□ Types check
□ Dependency rules pass
□ Architecture boundaries respected
□ SOLID principles followed
□ React patterns correct
□ NestJS patterns correct
□ No security issues
□ Performance acceptable
□ 100% test coverage maintained
□ Documentation updated