Error not properly thrown with bad stream definition for DynamoDB

[ktwbc]

If you have an error in serverless.yml defining a bad stream type, the Error message handler does not work because it itself creates a secondary error because of a missing array.

If your serverless.yml definition is:

myDynamoStream:
  description: DynamoDB Stream of changes to table
  handler: src/controller/streams.myDynamoStream
  stackTags:
    Project: star
  memorySize: 1024
  timeout: 900
  events:
    - stream:
        type: star
        arn:  arn:19123example

Here my "type" due to a copy and paste error is not dynamodb or kinesis which are the only accepted types. However the error on compile is:

TypeError: Cannot read property 'Policies' of undefined
at /Volumes/dev/myprojectnode_modules/serverless/lib/plugins/aws/package/compile/events/stream/index.js:258:62
at Array.forEach ()
at /Volumes/dev/myproject/node_modules/serverless/lib/plugins/aws/package/compile/events/stream/index.js:99:28
at Array.forEach ()
at AwsCompileStreamEvents.compileStreamEvents

This code:

 if (streamType === 'dynamodb') {
              dynamodbStreamStatement.Resource.push(EventSourceArn);
            } else if (streamType === 'kinesis') {
              if (event.stream.consumer) {
                kinesisStreamWithConsumerStatement.Resource.push(EventSourceArn);
              } else {
                kinesisStreamStatement.Resource.push(EventSourceArn);
              }
            } else {
              const errorMessage = [
                `Stream event of function '${functionName}' had unsupported stream type of`,
                ` '${streamType}'. Valid stream event source types include 'dynamodb' and`,
                " 'kinesis'. Please check the docs for more info.",
              ].join('');
              throw new this.serverless.classes.Properties.Policies[0].PolicyDocument.Error(
                errorMessage
              );
            }

Will fail because this.serverless.classes.Properties.Policies is undefined. This should be replaced with just a simple

 throw new Error(errorMessage); 

which will work and you get the proper error:

 Error: Stream event of function 'myDynamoStream' had unsupported stream type of 'star'. Valid stream event source types include 'dynamodb' and 'kinesis'. Please check the docs for more info.
      at /Volumes/dev/myproject/node_modules/serverless/lib/plugins/aws/package/compile/events/stream/index.js:257:21
      at Array.forEach (<anonymous>)
      at /Volumes/dev/myproject/node_modules/serverless/lib/plugins/aws/package/compile/events/stream/index.js:99:28
      at Array.forEach (<anonymous>)
   

I did a PR for this but the application process I don't have time to go through right now and write tests, so I'm just filing it.

serverless.yml

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⚠️⚠️ REPLACE WITH FULL COMMAND NAME output

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Installed version

⚠️⚠️ REPLACE WITH `serverless --version` OUTPUT

[medikoo]

@ktwbc great thanks for report.

Currently we're tackling such errors with config validation backed by JSON schema (and setting "configValidationMode: error will make process crash on any error, that'll become default at some point in a Framework).

Unfortunately we still don't have a schema for stream event type, see dedicated issue: #8034 (PR that implements it is welcome!)

I'm going to close it, as technically this will be solved with #8034