Feature: Warning on substitions without !Sub

cfn-lint version: 0.3.2

It’s pretty annoying if you add a substition and forget the !Sub:

          - Effect: "Allow"
            Action:
              - "s3:ReplicateObject"
              - "s3:ReplicateDelete"
            Resource:
              - "arn:aws:s3:::mycompany-${Environment}-mybucketname/*"

I’m not 100% sure if a ${value} always must be a substitution, since Cfn accepts this as valid string. But this could be a valid rule to give you a warning about this. Either you’re missing the !Sub or you picked a real annoying string to be used…

[kddejong]

This one is released now.

[cmmeyer]

I wonder if it makes sense to build a contextual for things like UserData where all bets are off – I mean, there’s nothing to stop you from injecting another CloudFormation template into a file via cfn-init in the EC2 metadata. What would THAT do to our linter?