feat: enhance AppSyncGraphQLResolver to pass context to resolver handlers and update tests for event and context access

Author: arnabrahman

packages/event-handler/src/appsync-graphql/AppSyncGraphQLResolver.ts

@@ -101,7 +101,7 @@ export class AppSyncGraphQLResolver extends Router {
       return;
     }
     try {
-      return await this.#executeSingleResolver(event);
+      return await this.#executeSingleResolver(event, context);
     } catch (error) {
       this.logger.error(
         `An error occurred in handler ${event.info.fieldName}`,
@@ -120,17 +120,25 @@ export class AppSyncGraphQLResolver extends Router {
    * with the event arguments. If no handler is found, it throws a `ResolverNotFoundException`.
    *
    * @param event - The AppSync GraphQL event containing resolver information.
+   * @param context - The Lambda execution context.
    * @throws {ResolverNotFoundException} If no resolver is registered for the given field and type.
    */
-  async #executeSingleResolver(event: AppSyncGraphQLEvent): Promise<unknown> {
+  async #executeSingleResolver(
+    event: AppSyncGraphQLEvent,
+    context: Context
+  ): Promise<unknown> {
     const { fieldName, parentTypeName: typeName } = event.info;
 
     const resolverHandlerOptions = this.resolverRegistry.resolve(
       typeName,
       fieldName
     );
     if (resolverHandlerOptions) {
-      return resolverHandlerOptions.handler.apply(this, [event.arguments]);
+      return resolverHandlerOptions.handler.apply(this, [
+        event.arguments,
+        event,
+        context,
+      ]);
     }
 
     throw new ResolverNotFoundException(

packages/event-handler/src/types/appsync-graphql.ts

@@ -1,14 +1,19 @@
+import type { Context } from 'aws-lambda';
 import type { RouteHandlerRegistry } from '../appsync-graphql/RouteHandlerRegistry.js';
 import type { GenericLogger } from './common.js';
 
 // #region Resolver fn
 
 type ResolverSyncHandlerFn<TParams = Record<string, unknown>> = (
-  args: TParams
+  args: TParams,
+  event: AppSyncGraphQLEvent,
+  context: Context
 ) => unknown;
 
 type ResolverHandlerFn<TParams = Record<string, unknown>> = (
-  args: TParams
+  args: TParams,
+  event: AppSyncGraphQLEvent,
+  context: Context
 ) => Promise<unknown>;
 
 type ResolverHandler<TParams = Record<string, unknown>> =

packages/event-handler/tests/unit/appsync-graphql/AppSyncGraphQLResolver.test.ts

@@ -1,4 +1,6 @@
 import context from '@aws-lambda-powertools/testing-utils/context';
+import { Context } from 'aws-lambda';
+import { AppSyncGraphQLEvent } from 'src/types/appsync-graphql.js';
 import { onGraphqlEventFactory } from 'tests/helpers/factories.js';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import { AppSyncGraphQLResolver } from '../../../src/appsync-graphql/AppSyncGraphQLResolver.js';
@@ -174,6 +176,34 @@ describe('Class: AppSyncGraphQLResolver', () => {
     });
   });
 
+  it('resolver function has access to event and context', async () => {
+    // Prepare
+    const app = new AppSyncGraphQLResolver({ logger: console });
+    app.resolver<{ id: string }>(
+      async ({ id }, event, context) => {
+        return {
+          id,
+          event,
+          context,
+        };
+      },
+      {
+        fieldName: 'getPost',
+      }
+    );
+
+    // Act
+    const event = onGraphqlEventFactory('getPost', 'Query', { id: '123' });
+    const result = await app.resolve(event, context);
+
+    // Assess
+    expect(result).toStrictEqual({
+      id: '123',
+      event,
+      context,
+    });
+  });
+
   it('emits debug message when AWS_LAMBDA_LOG_LEVEL is set to DEBUG', async () => {
     // Prepare
     vi.stubEnv('AWS_LAMBDA_LOG_LEVEL', 'DEBUG');