Feature request: support error handling in AppSync GraphQL

[dreamorosi]

Use case

The AppSync GraphQL resolver in Event Handler should allow customers to specify a

Solution/User Experience

The new feature should add a new method to the AppSyncGraphQLResolver class called exceptionHandler.

This method accepts an error class as first parameter (i.e. AssertionError) and a function handler as second:

import { AppSyncGraphQLResolver } from '@aws-lambda-powertools/event-handler/appsync-graphql';
import type { Context } from 'aws-lambda';

const app = new AppSyncGraphQLResolver({ logger });

app.exceptionHandler(AssertionError, async (error) => {
  return {
    message: 'Error foo occurred'
  }
});

app.onQuery('getTodo', async () => {
  throw new AssertionError('foo')

export const handler = async (event: unknown, context: Context) =>
  app.resolve(event, context);

Whenever an error in any of the other route handler is thrown, we should intercept it (around here) and check if there's any exception handler registered (we'll need a registry) that matches the error class being thrown.

If yes, we should call the exception handler and pass the error instance as first argument, and return its response as-is; if not, we should carry on the processing as it's implemented today.

The exceptionHandler() method should also be available as TypeScript class method decorator, similar to how onQuery() can.

Alternative solutions

Acknowledgment

• This feature request meets Powertools for AWS Lambda (TypeScript) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, Java, and .NET

Future readers

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[powertools-for-aws-oss-automation]

Note

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