Using cfnText on Tags to handle Fn

[WolfangAukang]

I have been trying this library and understanding how to replicate some Cloudformation templates into it. I found the following obstacle:

There are times I use !Sub on tags like this:

-   Key: Name
    Value: !Sub "${AWS::StackName}.mydomain.com"

The problem I see is that both key and value are defined as Text, according to Tag.dhall. I created a fork where I replaced the type with CfnText, so it is possible to perform this kind of operations into tags.

Is there any reason to use Text instead of CfnText for tags?

[jcouyang]

not often use Tag myself but from the doc can't tell it could be intrinsic fn https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-resource-tags.html

it kind of make sense to me that Value can be intrinsic fn, but does Key also support that?

[WolfangAukang]

Yes, at least if I try to use !Sub on the key, I have no complaints on CloudFormation. I know that logically it wouldn't make a lot of sense to use an operation on the key field, but it is possible.

[jcouyang]

btw, Tag.dhall is generated from code, so the correct place should be somewhere between

dhall-aws-cloudformation/src/Dhall/Cloudformation.hs

Lines 173 to 174 in 27b658e

	[("Key", Just $ makeRecordField D.Text),
	("Value", Just $ makeRecordField D.Text)],

pull request is welcome if you are keen to make the change
otherwise i can update it later when free

[WolfangAukang]

Perfect, I can create the PR