DI Refactoring Guide

The DI Pipeline (follow every step)

Step 1: Define the Interface

Create src/interfaces/IMyService.ts:

export interface IMyService {
  doWork(input: string): Promise<Result>;
  getStatus(): ServiceStatus;
}

Step 2: Create the Symbol Token

Add to src/core/tokens.ts:

export const IMyService = Symbol('IMyService');

Step 3: Export from Barrel

Add to src/interfaces/index.ts:

export { IMyService } from './IMyService';

Step 4: Implement the Concrete Class

Constructor accepts interfaces via DI, never concrete classes:

export class DefaultMyService implements IMyService {
  constructor(
    private readonly logger: ILogger,
    private readonly config: IConfigProvider,
  ) {}
  
  async doWork(input: string): Promise<Result> {
    this.logger.info('Processing', { input });
    // implementation
  }
}

Step 5: Register in Composition Root

Add to src/composition.ts:

container.registerSingleton<IMyService>(Tokens.IMyService, (c) => {
  const logger = c.resolve<ILogger>(Tokens.ILogger);
  const config = c.resolve<IConfigProvider>(Tokens.IConfigProvider);
  return new DefaultMyService(logger, config);
});

Step 6: Resolve (never new in business logic)

const myService = container.resolve<IMyService>(Tokens.IMyService);

VS Code API Abstraction

Never call vscode.* in business logic. Use adapter interfaces:

Only these files may import vscode directly:

• •src/vscode/adapters.ts, src/extension.ts, src/composition.ts, src/ui/**

Existing Tokens (don't duplicate)

ILogger, IGitOperations, IProcessMonitor, IConfigProvider, IDialogService, IClipboardService, IPulseEmitter, IProcessSpawner, ICopilotRunner, IEnvironment, IGlobalCapacity, IPlanConfigManager, IEvidenceValidator, IMcpManager, INodeRunner, INodeExecutor, INodeStateMachine, IFileSystem

Logger Pattern

The one acceptable service locator — static factory initialized in composition root:

const log = Logger.for('my-component');
log.info('Started', { context });

Checklist

• • Interface defined in src/interfaces/
• • Token created in src/core/tokens.ts
• • Exported from src/interfaces/index.ts
• • Constructor takes interfaces, not concrete classes
• • Registered in src/composition.ts
• • No new ConcreteClass() in business logic
• • No direct vscode.* calls in business logic
• • Unit tests mock via interfaces