aws-appsync: javascript resolver support

[mtliendo]

Describe the feature

Based on this RFC, it would nice to explore what a CDK supported candidate would look like.

Use Case

I'd like the experimental L2 construct to support the JS runtime for AppSync resolvers

Proposed Solution

the datasource.createResolver() method should accept a code argument, a specified runtime, and make the mappingTemplates optional.

From this:

const appsyncFunction = new appsync.AppsyncFunction(this, 'function', {
  name: 'appsync_function',
  api,
  dataSource: api.addNoneDataSource('none'),
  requestMappingTemplate: appsync.MappingTemplate.fromFile('request.vtl'),
  responseMappingTemplate: appsync.MappingTemplate.fromFile('response.vtl'),
});

const pipelineResolver = new appsync.Resolver(this, 'pipeline', {
  api,
  dataSource: api.addNoneDataSource('none'),
  typeName: 'Query',
  fieldName: 'getDemos',
  requestMappingTemplate: appsync.MappingTemplate.fromFile('beforeRequest.vtl'),
  pipelineConfig: [appsyncFunction],
  responseMappingTemplate: appsync.MappingTemplate.fromFile('afterResponse.vtl'),
});

To this:

const appsyncFunction = new appsync.AppsyncFunction(this, 'function', {
  name: 'appsync_function',
  api, 
  dataSource: api.addNoneDataSource('none'),
  runtime:  appsync.Runtime.APPSYNC_JS,
  code: appsync.Code.fromAsset(path.join(__dirname, 'fn1.js'))
});

const pipelineResolver = new appsync.Resolver(this, 'pipeline', {
  api,
  dataSource: api.addNoneDataSource('none'),
  typeName: 'Query',
  fieldName: 'getDemos',
  code: appsync.Code.fromAsset(path.join(__dirname, 'pipelineMappings.js'))
  pipelineConfig: [appsyncFunction],
});

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.50.0

Environment details (OS name and version, etc.)

macOS

[peterwoodworth]

We're bound by the CloudFormation API which requires a template within the CloudFormation template, or requires the template to reside in S3. I'm not sure how exactly we'd be able to implement this feature, or how this would be useful given the CloudFormation requirements. Could you explain exactly how this would be useful and how we might be able to accomplish this feature?

[garretcharp]

Not really sure how cloudformation actually works but this would be the absolute most useful feature for appsync. VTL is really annoying to work with compared to javascript

[mtliendo]

We on the AppSync team would be happy to help push this PR through based on our new release today 😊

https://aws.amazon.com/blogs/aws/aws-appsync-graphql-apis-supports-javascript-resolvers/

[piotrmoszkowicz]

According to https://github.com/aws/aws-cdk/blob/04baba88b4e27e19b7d0ab237ff641043d089edc/packages/%40aws-cdk/cfnspec/spec-source/specification/000_cfn/000_official/000_AWS_AppSync.json which is currently being merged, there's Code, CodeS3Location and Runtime (with Name and RuntimeVersion properties), which could be used for that. I assume we can implement it. I can volunteer for that, but could do Sunday / beginning of next week, but would love to help!

[piotrmoszkowicz]

Also for Code - we could partially take a look on https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda.Code.html and copy part of it (ie. fromInline, fromAsset, fromDockerImage and fromBucket). Also would be nice to take a look at https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda_nodejs-readme.html and enable bundling via esbuild - I would love to have that feature!

[fab-mindflow]

👍 strongly interested in this support at our startup already heavily using AppSync w/ CDK.

[mtliendo]

@piotrmoszkowicz I have a CDK repo up (can finally make public 😅 ) that uses the L1 construct in conjunction with the addOverrides property to enable support for JS resolvers. The overrides are only needed due to the latest CloudFormation updates not being merged into the CDK yet (I think this may happen some time next week)

The main points to call out are when I create a function, add the overrides and then create create the pipeline, then and those overrides.

Would you be interested in making this contribution to the L2 alpha construct?