How to get S3 bucket name from S3 ARN using cloudformation

Question

I'm using the expression ,Select [5: ,Split [':', !Ref ResourceARN]] to convert ResourceARN , which is a STRING input parameter to a stack, to the corresponding S3 bucket name , to pass it to a child stack.

Example: from arn:aws:s3:::tests3bucket-1a3o2v3wr375g expecting to create tests3bucket-1a3o2v3wr375g

Instead it evaluates to empty string, as I'm getting Parameters: [S3BucketName] must have values .

How can I make this work?

---

Here is the main stack template:

AWSTemplateFormatVersion: 2010-09-09
Parameters:
  ResourceARN:
    Description: 'The AWS ARN associated with S3 resource, example arn:aws:s3:::tests3bucket-1a3o2v3wr375g'
    ConstraintDescription: The ARN of the resource
    Type: String
:
:
Resources:
  ChildStack:
    Type: 'AWS::CloudFormation::Stack'
    Properties:
      TemplateURL: !Sub >-
        https://${QSS3BucketName}.s3.amazonaws.com/${QSS3KeyPrefix}/templates/child.template
      Parameters:
        S3BucketName: !Select [5, !Split [':', !Ref ResourceARN]] # Expecting to evaluate to tests3bucket-1a3o2v3wr375g
:
:

and here is the child template:

AWSTemplateFormatVersion: 2010-09-09
Parameters:
  S3BucketName:
    Description: 'The name of the S3 bucket'
    Type: String
:
:

Answer 1

Thank you @berenbums for taking a look - just realized myself too that this works. There was another issue which masked the problem.

So after all, the expression ,Select [5: ,Split [':', !Ref ResourceARN]] can be used to convert ResourceARN to the corresponding S3 bucket name.