Fn::Join Broken

[dulac]

I’ve really been enjoying using Goformation! I found a bug recently though that I’m not sure how to fix (I'm still learning Golang), but I tracked down the reason, and figured you might immediately know how to fix.

Summary: The Fn::Join is not joining values together. I've traced this down to find that it is not reading the array inside the array. I believe the "goformation/intrinsics/fnjoin.go" file needs to be updated to loop the inner array. Let me know if you’d like me to put this in Github Issues

# TROUBLESHOOTING WALKTHROUGH

Example CF snippet from the example template in the repo:

Role:
  Fn::ImportValue:
   !Join ['-', [!Ref 'ProjectId', !Ref 'AWS::Region', 'LambdaTrustRole']]

If you try to unmarshall, and output the function.Role, it gives you nothing:

   > 2018/05/12 08:40:09 Found a AWS::Serverless::Function named GetHelloWorld (Role: )

Let's remove the ImportValue function:

   Role: !Join ['-', [!Ref 'ProjectId', !Ref 'AWS::Region', 'LambdaTrustRole']]

If you try to unmarshall this again, and output the function.Role as before, it gives you just "-":

   > 2018/05/12 08:40:34 Found a AWS::Serverless::Function named GetHelloWorld (Role: -)

So then for fun, I removed the inner array, and this worked:

   Role: !Join ['-', !Ref 'AWS::Region']

The output is:

   > 2018/05/12 08:42:03 Found a AWS::Serverless::Function named GetHelloWorld (Role: -us-east-1)

However, this syntax is in invalid.

I'm pretty sure the "goformation/intrinsics/fnjoin.go" file needs to loop the inner array.

Thanks!

[PaulMaddox]

You're right. Currently Fn::Join implementation is not the same as CloudFormation's implementation - I'm not sure what was going through my mind when I wrote that!

Instead of joining the strings together, it should use the delimiter to join all of the elements of the array.

I'll write some tests and a fix for this now.