Change CFN behavior when there are two output elements of the same name and affected by conditions.

[bbergero]

1. Title -> Change CFN behavior when there are two output elements of the same name and affected by conditions.

2. Scope of request -> Currently two outputs like:

   "Output1" : {
      "Condition" : "IsCondition",
      "Value" : "SomeValue"
   },
   "Output1" : {
      "Condition" : "IsNotCondition,
      "Value" : "OtherValue"
   }

   No output is created.

3. Expected behavior -> The expected behavior would be that if more than one output by the same name is defined AFTER conditions as applied, then an error should be produced, and if only one resulted, that would be the one being created. We try to use this scheme to have a template produce different outputs depending on a condition that affected the resources that got created. We work around this issue using exports with the same name in two outputs of different names, but in some scenarios, such as when using Terraform data sources, the output name is what gets exposed and would need to be the same. In any case, the behavior of not producing any error but silently missing the output, creates errors further down the deployment pipeline that are harder to diagnose.

[benbridts]

@bbergero You can use the Fn::If function in the output value. Here is a snippet and a full example in yaml:

Output:
    Value: !If [IsCondition, "SomeValue", "OtherValue"]

---

---
Parameters:
  OutputSelector:
    Type: String
    Default: First
    AllowedValues:
    - First
    - Second
Conditions:
  IsFirst: !Equals [!Ref OutputSelector, "First"]
Resources:
  Dummy:
    Type: AWS::CloudFormation::WaitConditionHandle
Outputs:
  Output:
    Description: Based on OutputSelector
    Value: !If [IsFirst, "First selected", "Second selected"]

[luiseduardocolon]

@bbergero were you able to use the suggestion from @ikben ? Do you get any error from the linter?

[bbergero]

Awaiting from DXC, thanks

Regards,

Bernard

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From: Luis Eduardo Colon notifications@github.com Reply to: aws-cloudformation/aws-cloudformation-coverage-roadmap reply@reply.github.com Date: Friday, 29 May 2020 at 02:09 To: aws-cloudformation/aws-cloudformation-coverage-roadmap aws-cloudformation-coverage-roadmap@noreply.github.com Cc: Bergeron Bernard bbergero@amazon.co.uk, Mention mention@noreply.github.com Subject: Re: [aws-cloudformation/aws-cloudformation-coverage-roadmap] Change CFN behavior when there are two output elements of the same name and affected by conditions. (#478)

@bbergerohttps://github.com/bbergero were you able to use the suggestion from @ikbenhttps://github.com/ikben ? Do you get any error from the linter?

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[benbridts]

@luiseduardocolon IIRC I was able to deploy that example

[gbourniq]

This works!