Return undefined with new variable resolver engine

Serverless Framework
1

We’re trying to migrate from the v2 variable resolvers to the new v3 variable resolver engine. I’m struggling with how to return undefined values (i.e. my resolver can’t resolve).

If I return { value: undefined }, serverless gives error:
Source "xyz" returned not supported result: "undefined"

If I return just undefined (i.e. not wrapped in { value }), serverless gives error:
Unexpected "xyz" source result: undefined

If I return { value: null }, serverless gives error:
Value not found at "xyz" source

For context, I want to use this to pass an optional parameter:

    MyLayer:
      Type: AWS::Lambda::LayerVersion
      Properties:
        Content:
          S3Bucket: ${myresolver:bucket, ''}
          S3Key: ${myresolver:key, ''}
          S3ObjectVersion: ${myresolver:objectVersion}

Any advice?

1 Like
2

Getting the same problem. It also happens when resolving ssm secrets that don’t exist. It fails rather than using the provided default ’ ’

Blocking deployment now.

3

Ok found a solution by looking at how serverless do it. If your variable doesn’t exist your resolve needs to

return { value: null}

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It looks like you’ve tried this, so unclear why you still get an error.