Fn::Join in Fn::Sub

[rschick]

I've been having problems with doing this style of include for UserData:

UserData:
  Fn::Base64:
    Fn::Sub:
      !Include { type: literal, location: userdata.sh }

It fails validation with:

An error occurred (ValidationError) when calling the ValidateTemplate operation: 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

It looks like an issue with CF. The output looks fine:

        "UserData": {
          "Fn::Base64": {
            "Fn::Sub": {
              "Fn::Join": [
                "",
                [
                  "#!/bin/bash -xe\n",
                 ...
                ]
              ]
            }
          }
        }

I am currently working around this by including the userdata script as a string literal in my YAML:

      UserData:
        !Base64
          Fn::Sub: |
            #!/bin/bash -xe
            ...

But I'd like to be able to !Include it instead.

I was thinking of making a PR to add another type of include that wouldn't use the Fn::Join method, and instead just join the script with newlines into a single string. I'll put something together and let you know if it works.

Thanks for the great tool!

[monken]

Thank you very much for reporting and fixing this issue. I have made some changes:

• type: string will not support the context property. This makes the API more consistent as !Refs would not be supported which is really the primary use case for variables in includes. Fn::Sub supports custom variables out of the box so I think that should be the default.
• I deprecated type: literal altogether. The Fn::Sub syntax is superior and should be used going forward.

Let me know what you think and I will cut a release of you are happy!

[monken]

released