Unable to specify AWS::NoValue for Domain property of AWS::Serverless::Api

[selcukcihan]

Description:

I'd like to selectively create a custom domain for an API, based on a condition. This currently fails with:

Custom Domains only works if both DomainName and CertificateArn are provided.

Steps to reproduce:

Resources:
  MyApi:
    Type: AWS::Serverless::Api
    Properties:
      EndpointConfiguration:
        Type: EDGE
      Domain: !If [UseCustomDomain, !Ref "AWS::NoValue", !Ref "AWS::NoValue"]

Parameters:
  TemporaryStack:
    Type: String
    Default: "FALSE"
    AllowedValues:
      - "FALSE"
      - "TRUE"
    Description: Specify "TRUE" if the stack is for a temporary branch.

Conditions:
  UseCustomDomain: !Equals 
    - !Sub "${TemporaryStack}"
    - "FALSE"

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: macOS Catalina
2. If using SAM CLI, sam --version: SAM CLI, version 1.24.0
3. AWS region: eu-west-1

[CoshUS]

Reproduced. The Domain property in SAM currently does not support intrinsics.

[brysontyrrell]

This is a recurring issue around conditional attributes. See #1435 and #1955

[hoffa]

You might be able to get this to work by adding AWS::LanguageExtensions to Transform as such:

Transform:
  - AWS::LanguageExtensions
  - AWS::Serverless-2016-10-31

AWS::LanguageExtensions resolves intrinsic functions if the value is known when Transforms are run.

See #2533 for more information.

[hoffa]

Closing in favor of #2533.