Fn::Sub Error / Incompatibility with serverless-pseudo-parameters

[alastairmccormack]

When trying to use custom request templates for Kinesis with the following syntax:

custom:
  apiGatewayServiceProxies:
    - kinesis:
        path: /kinesis
        method: post
        streamName: { Ref: 'MyStream' }
        request:
          template:
            text/plain:
              Fn::Sub:
                - |
                  #set($msgBody = $util.parseJson($input.body))
                  #set($msgId = $msgBody.MessageId)
                  {
                      "Data": "$util.base64Encode($input.body)",
                      "PartitionKey": "$msgId",
                      "StreamName": "#{MyStreamArn}"
                  }
                - MyStreamArn:
                    Fn::GetAtt: [MyStream, Arn]

I was getting the following error:

The CloudFormation template is invalid: Template error: One or more Fn::Sub intrinsic functions don't specify expected arguments. Specify a string as first argument, and an optional second argument to specify a mapping of values to replace in the string

After much digging, I found that this was due to an incompatibility with serverless-pseudo-parameters plugin. Uninstalling serverless-pseudo-parameters resolved the issue.

I think we need a warning in the documentation or, even better, some kind of compatibility.

[johnmee]

Might be able to close this one since sls v3 is not, will never be, compatible with serverless-pseudo-parameters. Although I'm not saying this will certainly work now.