feat(event-handler): Add includeRouter and context sharing support to AppSync GraphQL resolver

[arnabrahman]

Summary

This PR adds the ability for router composition and sharing context data between routes

Changes

Follows the impmentation provided in the linked issue description.

• includeRouter method for router composition
• appendContext method for appending context that is shared with all the routes
• new context option is set as sharedContext, this is up for debate
• 100% unit test coverage
• Documentation added, mostly followed what we have in python documentation

// Schema
type Post {
	id: ID
	title: String
	content: String
	requestId: String
}

type User {
	id: ID
	name: String
	email: AWSEmail
	requestId: String
}

type Query {
	getUsers: [User]
	getPosts: [Post]
}

schema {
	query: Query
}

//postRouter.ts
import { Router } from '@aws-lambda-powertools/event-handler/appsync-graphql';

const postRouter = new Router();

postRouter.onQuery('getPosts', async (args, { sharedContext }) => {
  const requestId = sharedContext?.get('requestId');
  return [{ id: 1, title: 'First post', content: 'Hello world!', requestId }];
});

export { postRouter };

// userRouter.ts
import { Router } from '@aws-lambda-powertools/event-handler/appsync-graphql';

const userRouter = new Router();

userRouter.onQuery('getUsers', async (args, { sharedContext }) => {
  const requestId = sharedContext?.get('requestId');
  return [{ id: 1, name: 'John Doe', email: '[email protected]', requestId }];
});

export { userRouter };

// app.ts
import { AppSyncGraphQLResolver } from '@aws-lambda-powertools/event-handler/appsync-graphql';
import { Logger } from '@aws-lambda-powertools/logger';
import type { Context } from 'aws-lambda';
import { userRouter } from './userRouter.js';
import { postRouter } from './todoRouter.js';

const logger = new Logger({ serviceName: 'GraphQLAPI' });
const app = new AppSyncGraphQLResolver({ logger });

app.includeRouter([userRouter, postRouter]);

export const handler = async (event: unknown, context: Context) => {
  app.appendContext({ 
    isAdmin: true, 
    requestId: 'request-123',
    timestamp: Date.now()
  });
  
  return app.resolve(event, context);
};

query MyQuery {
  getUsers {
    id,
    name,
    email,
    requestId
  }
}

{
  "data": {
    "getUsers": [
      {
        "id": "1",
        "name": "John Doe",
        "email": "[email protected]",
        "requestId": "request-123"
      }
    ]
  }
}

query MyQuery {
  getPosts {
    id,
    title,
    content,
    requestId
  }
}

{
  "data": {
    "getPosts": [
      {
        "id": "1",
        "title": "First post",
        "content": "Hello world!",
        "requestId": "request-123"
      }
    ]
  }
}

Issue number: closes #4131

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[arnabrahman]

Changed this to follow the convention of private methods in this project. I missed this in my last PR.

[dreamorosi]

We have updated the linting rules of the project to make them a bit stricter - this should make reviewing contributions easier on both sides since you can now catch issues both with pre-commit hooks and CI here on the PR.

You might need to rebase and address the issues in the new code to get the CI green.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
5.0% Duplication on New Code

See analysis details on SonarQube Cloud