Documentation And Adrs

文档与 ADR

概览

记录的不只是代码，更要记录决策。最有价值的文档，保存的是 why，也就是做出这个决定时的背景、约束和权衡。代码展示了 what 被构建出来，文档解释了 why it was built this way，以及 what alternatives were considered。这些背景信息，对未来继续维护代码库的人类和 agent 都至关重要。

何时使用

• 做重要的架构决策
• 在多个方案之间做选择
• 新增或修改公开 API
• 发布会改变用户可见行为的功能
• 帮助新成员或新 agent 理解项目
• 当你发现自己在重复解释同一件事时

不适用的场景： 不要为显而易见的代码写文档；不要写只是复述代码内容的注释；也不要给一次性原型写厚重文档。

架构决策记录（ADR）

ADR 用于记录重要技术决策背后的推理过程。它们是你能写出的最高价值文档之一。

什么时候该写 ADR

• 选择框架、库或关键依赖
• 设计数据模型或数据库 schema
• 确定认证策略
• 决定 API 架构，例如 REST、GraphQL 或 tRPC
• 在构建工具、托管平台或基础设施之间做选择
• 任何将来回滚代价很高的决策

ADR 模板

将 ADR 按顺序编号，存放在 docs/decisions/ 中：

# ADR-001: Use PostgreSQL for primary database

## Status
Accepted | Superseded by ADR-XXX | Deprecated

## Date
2025-01-15

## Context
We need a primary database for the task management application. Key requirements:
- Relational data model (users, tasks, teams with relationships)
- ACID transactions for task state changes
- Support for full-text search on task content
- Managed hosting available (for small team, limited ops capacity)

## Decision
Use PostgreSQL with Prisma ORM.

## Alternatives Considered

### MongoDB
- Pros: Flexible schema, easy to start with
- Cons: Our data is inherently relational; would need to manage relationships manually
- Rejected: Relational data in a document store leads to complex joins or data duplication

### SQLite
- Pros: Zero configuration, embedded, fast for reads
- Cons: Limited concurrent write support, no managed hosting for production
- Rejected: Not suitable for multi-user web application in production

### MySQL
- Pros: Mature, widely supported
- Cons: PostgreSQL has better JSON support, full-text search, and ecosystem tooling
- Rejected: PostgreSQL is the better fit for our feature requirements

## Consequences
- Prisma provides type-safe database access and migration management
- We can use PostgreSQL's full-text search instead of adding Elasticsearch
- Team needs PostgreSQL knowledge (standard skill, low risk)
- Hosting on managed service (Supabase, Neon, or RDS)

ADR 生命周期

PROPOSED → ACCEPTED → (SUPERSEDED or DEPRECATED)

• 不要删除旧 ADR。 它们保存了历史上下文。
• 如果决策发生变化，写新的 ADR，并引用与替代旧 ADR。

内联文档

什么时候该写注释

注释要解释 why，而不是 what：

// BAD: Restates the code
// Increment counter by 1
counter += 1;

// GOOD: Explains non-obvious intent
// Rate limit uses a sliding window — reset counter at window boundary,
// not on a fixed schedule, to prevent burst attacks at window edges
if (now - windowStart > WINDOW_SIZE_MS) {
  counter = 0;
  windowStart = now;
}

什么时候不要写注释

// 不要给一看就懂的代码加注释
function calculateTotal(items: CartItem[]): number {
  return items.reduce((sum, item) => sum + item.price * item.quantity, 0);
}

// 不要留下其实现在就该做掉的 TODO
// TODO: add error handling  ← 直接补上

// 不要保留被注释掉的旧代码
// const oldImplementation = () => { ... }  ← 删掉，git 有历史

记录已知陷阱

/**
 * IMPORTANT: This function must be called before the first render.
 * If called after hydration, it causes a flash of unstyled content
 * because the theme context isn't available during SSR.
 *
 * See ADR-003 for the full design rationale.
 */
export function initializeTheme(theme: Theme): void {
  // ...
}

API 文档

对于公开 API，例如 REST、GraphQL 或库接口：

和类型写在一起（TypeScript 首选）

/**
 * Creates a new task.
 *
 * @param input - Task creation data (title required, description optional)
 * @returns The created task with server-generated ID and timestamps
 * @throws {ValidationError} If title is empty or exceeds 200 characters
 * @throws {AuthenticationError} If the user is not authenticated
 *
 * @example
 * const task = await createTask({ title: 'Buy groceries' });
 * console.log(task.id); // "task_abc123"
 */
export async function createTask(input: CreateTaskInput): Promise<Task> {
  // ...
}

REST API 用 OpenAPI / Swagger

paths:
  /api/tasks:
    post:
      summary: Create a task
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateTaskInput'
      responses:
        '201':
          description: Task created
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Task'
        '422':
          description: Validation error

README 结构

每个项目都应该有一个 README，至少覆盖：

# Project Name

One-paragraph description of what this project does.

## Quick Start
1. Clone the repo
2. Install dependencies: `npm install`
3. Set up environment: `cp .env.example .env`
4. Run the dev server: `npm run dev`

## Commands
| Command | Description |
|---------|-------------|
| `npm run dev` | Start development server |
| `npm test` | Run tests |
| `npm run build` | Production build |
| `npm run lint` | Run linter |

## Architecture
Brief overview of the project structure and key design decisions.
Link to ADRs for details.

## Contributing
How to contribute, coding standards, PR process.

Changelog 维护

对于已经发布的功能：

# Changelog

## [1.2.0] - 2025-01-20
### Added
- Task sharing: users can share tasks with team members (#123)
- Email notifications for task assignments (#124)

### Fixed
- Duplicate tasks appearing when rapidly clicking create button (#125)

### Changed
- Task list now loads 50 items per page (was 20) for better UX (#126)

面向 Agent 的文档

对 AI agent 还要额外考虑以下文档：

• CLAUDE.md / rules files：记录项目约定，让 agent 按你的方式工作
• Spec files：保持 spec 最新，让 agent 构建正确的东西
• ADRs：帮助 agent 理解决策背景，避免它重复讨论旧结论
• Inline gotchas：防止 agent 掉进已知坑里

常见自我安慰

危险信号

• 架构决策没有任何书面理由
• 公开 API 没有文档或类型说明
• README 没解释项目怎么跑起来
• 用注释掉的旧代码代替删除
• TODO 注释挂了几周都没处理
• 一个有明显架构选择的项目却没有 ADR
• 文档只是复述代码，而不是解释意图

验证

写完文档后，确认：

• 所有重要架构决策都有 ADR
• README 覆盖 quick start、commands 和 architecture overview
• API 函数有参数与返回值说明
• 重要 gotcha 已在真正相关的位置用内联文档记录
• 没有残留被注释掉的旧代码
• 规则文件（CLAUDE.md 等）内容是最新且准确的