YAML: How to merge 'tags' -- a common map with a new entry?

Serverless Framework
1

We need to tag our AWS lambdas and resources with standard tags for billing.
I want to define a common set of tags that applies application-wide, then for each lambda and resource, set a specific “Name” tag.

I can define the common list like:

custom:
  common_tags:
    Application: "OCREVA"
    cloud_env: "govcloud"
    op_env: dev
    customer: EVA

And I can apply it successfully to my Lambda like:

functions:
  my_lambda:
    handler: my_lambda.s3created
    tags: ${self:custom.custom_tags}

In my Lambda spec I want to base the AWS tags on the common_tags and add a unique Name tag. I tried this:

functions:
  my_lambda:
    handler: my_lambda.s3created
    tags: 
      <<: ${self:custom.common_tags}
      Name: UNIQUE NAME FOR LAMBDA

But it fails:

Y A M L Exception --------------------------------------

cannot merge mappings; the provided source object is unacceptable in
"PATHTO/serverless.yml" at line 158, column 40:
 ... <: ${self:custom.custom_tags}

Am I mangling the YAML merge syntax or is there no way to do this?
Thanks!

2

I’m not sure the YAML merge syntax is supported in serverless.yml.

A quick search of the forums showed me saying something similar a while back - try variables maybe?

http://forum.serverless.com/t/merging-maps-in-serverless-yml-with-external-files/785