solid

SOLID Principles - Clean Architecture Reference

Based on "Clean Architecture" by Robert C. Martin, Chapter 7-11 (pages 57-90)

Persona

Read .claude/roles/architect.md — adopt this profile and follow all its rules.

When to Activate

This skill activates for:

• Code review with design concerns
• Refactoring decisions
• Designing new modules or components
• Evaluating class/function responsibilities

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SRP: Single Responsibility Principle

"A module should have one, and only one, reason to change." — Clean Architecture, p.62

Definition

A module should be responsible to one, and only one, actor (stakeholder/user group).

In ReviewFlow

// ❌ Bad: one class, three actors driving change
//   - the developer (trigger flow)
//   - the platform integration (GitLab/GitHub API)
//   - the dashboard (stats persistence)
class ReviewService {
  async triggerReview(mr: TrackedMr): Promise<void> {
    /* developer concern: enqueue a review job */
  }
  async fetchThreads(mrId: MergeRequestId): Promise<Thread[]> {
    /* platform concern: hit GitLab/GitHub API */
  }
  async saveStats(stats: ReviewStats): Promise<void> {
    /* dashboard concern: persist aggregated metrics */
  }
}

// ✅ Good: one module per actor
export class TriggerReviewUseCase implements UseCase<TriggerReviewInput, void> {
  constructor(private readonly queue: QueueGateway) {}
  async execute(input: TriggerReviewInput): Promise<void> {
    await this.queue.enqueue(input);
  }
}

export interface ThreadFetchGateway {
  fetch(mrId: MergeRequestId): Promise<Thread[]>;
}

export class ReviewStatsPresenter {
  present(stats: ReviewStats): ReviewStatsViewModel {
    return { average: stats.averageScore, total: stats.totalReviews };
  }
}

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OCP: Open-Closed Principle

"A software artifact should be open for extension but closed for modification." — Clean Architecture, p.70

Definition

You should be able to change the behavior of a module by adding new code, not changing existing code.