Error message for "AWS::Serverless::Application" resource with "Fn::FindInMap"

[ylynn]

Description:

Error message for "AWS::Serverless::Application" resource with "Fn::FindInMap" is "TypeError: unhashable type: 'list'", which is not helpful.

Steps to reproduce the issue:
Parts of the template

Parameters:
  SemVer:
    Type: String
    Default: 1.0.0

Mappings:
  MyMap:
    appId:
      appIdValue: arn:aws:serverlessrepo:us-east-1:1234xxx:applications/anotherApp
    version:
      versionValue:
      - Ref: Semver

Resources:
  myApp:
    Type: AWS::Serverless::Application
    Properties:
      Location:
        ApplicationId:
          Fn::FindInMap:
          - MyMap
          - appId
          - appIdValue
        SemanticVersion:
          Fn::FindInMap:
          - MyMap
          - version
          - versionValue

Observed result:
TypeError: unhashable type: 'list'

Expected result:

[mateuszowolf]

I think it might be this part

version:
    versionValue
    - Ref: Semver

which should look like this:

version:
    versionValue: !Ref Semver

[hoffa]

You might be able to get this to work by adding AWS::LanguageExtensions to Transform as such:

Transform:
  - AWS::LanguageExtensions
  - AWS::Serverless-2016-10-31

AWS::LanguageExtensions resolves intrinsic functions if the value is known when Transforms are run.

See #2533 for more information.

[hoffa]

Closing in favor of #2533.