Amplify-cli: Custom Resolver generator from cli.

[yareyaredesuyo]

Now, when making custom resolver, it requires some copy and paste tasks.

So, i think it maybe good idea to generate custom resolver code's from cli.

[kaustavghosh06]

@yareyaredesuyo Could you mention which specific tasks in details? Would love to know more about this in detail to improve the dev experience.

[yareyaredesuyo]

For example, when making custom resolver in cli.

Use a command like

amplify generate resolver --type Lambda --name Echo 

and it generates these kind of files.

Resources

"EchoLambdaDataSource": {
  "Type": "AWS::AppSync::DataSource",
  "Properties": {
    "ApiId": {
      "Ref": "AppSyncApiId"
    },
    "Name": "EchoFunction",
    "Type": "AWS_LAMBDA",
    "ServiceRoleArn": {
      "Fn::GetAtt": [
        "EchoLambdaDataSourceRole",
        "Arn"
      ]
    },
    "LambdaConfig": {
      "LambdaFunctionArn": {
        "Fn::Sub": [
          "arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:echofunction-${env}",
          { "env": { "Ref": "env" } }
        ]
      }
    }
  }
}

"QueryEchoResolver": {
  "Type": "AWS::AppSync::Resolver",
  "Properties": {
    "ApiId": {
      "Ref": "AppSyncApiId"
    },
    "DataSourceName": {
      "Fn::GetAtt": [
        "EchoLambdaDataSource",
        "Name"
      ]
    },
    "TypeName": "Query",
    "FieldName": "echo",
    "RequestMappingTemplateS3Location": {
      "Fn::Sub": [
        "s3://${S3DeploymentBucket}/${S3DeploymentRootKey}/resolvers/Query.echo.req.vtl",
        {
          "S3DeploymentBucket": {
            "Ref": "S3DeploymentBucket"
          },
          "S3DeploymentRootKey": {
            "Ref": "S3DeploymentRootKey"
          }
        }
      ]
    },
    "ResponseMappingTemplateS3Location": {
      "Fn::Sub": [
        "s3://${S3DeploymentBucket}/${S3DeploymentRootKey}/resolvers/Query.echo.res.vtl",
        {
          "S3DeploymentBucket": {
            "Ref": "S3DeploymentBucket"
          },
          "S3DeploymentRootKey": {
            "Ref": "S3DeploymentRootKey"
          }
        }
      ]
    }
  }
}

resolvers/Query.echo.req.vtl

{
    "version": "2017-02-28",
    "operation": "Invoke",
    "payload": {
        "type": "Query",
        "field": "echo",
        "arguments": $utils.toJson($context.arguments),
        "identity": $utils.toJson($context.identity),
        "source": $utils.toJson($context.source)
    }
}

resolvers/Query.echo.res.vtl

$util.toJson($ctx.result)

It will reduce the cost of copying paste tasks, when making custom resolvers.

[kaustavghosh06]

@yareyaredesuyo If you're interested, this would be a great candidate for a 3rd party plugin. Here are some docs to get you started with - https://aws-amplify.github.io/docs/cli/plugins?sdk=js