AWS: cloudformation CommaDelimitedList and manual list not matching - amazon-web-services

Question

I'm trying to create a cloudformation template that has default values, and I'm running a few !Sub functions to replace imported parameters into the template.
However, I am passing a list to a nodejs Lambda function that I need to !Sub before sending it.
The code that I'm writing:
AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: Creating Athena database and tables
Parameters:
S3DataLocations:
Type: CommaDelimitedList
Description: The S3 locations where the logs are read from (Specify 'Use,Default' to inherit defaults)
Default: Use,Default
Conditions:
CustomS3DataLocations: !Equals ['Use,Default', !Join [",", !Ref S3DataLocations]]
Resources:
# Custom resource for running CreateTableFunction, to create databases
CreateLogTable:
Type: Custom::CreateLogTable
Properties:
ServiceToken: !GetAtt [CreateLogTableFunction, Arn]
S3DataLocations:
Fn::If:
- CustomS3DataLocations
- !Split
- ","
- !Sub
- s3://${LoggingBucket}/data/ApplicationLogs1/,
s3://${LoggingBucket}/data/ApplicationLogs2/,
s3://${LoggingBucket}/data/ApplicationLogs3/
- { LoggingBucket: !ImportValue Parent-LoggingBucket}
- !Ref S3DataLocations
If I pass these as a literal external DataTypes parameter s3://logbucket/data/ApplicationLogs1/,s3://logbucket/data/ApplicationLogs2/,s3://logbucket/data/ApplicationLogs3/ it works fine and translates to ["s3://logbucket/data/ApplicationLogs1/","s3://logbucket/data/ApplicationLogs2/","s3://logbucket/data/ApplicationLogs3/"] and is interpreted by the Lambda without issue.
The parameter gets parsed through the CommaDelimitedList type and is passed to the Lambda without issue.
The issue arises in that I am trying to create a manual default, so I need to !Sub a list, as a string, then !Split to be passed as an actual list to the Custom Lambda. This doesn't seem to be working every way I try it and I cannot figure why.
I've been inspecting the success (manual param) and failure (defaults, without manual param) and I cant see a big difference.
The event of the lambda shows, when working:
{
"RequestType": "Create",
"ServiceToken": "hidden",
"ResponseURL": "hidden",
"StackId": "hidden",
"RequestId": "hidden",
"LogicalResourceId": "CreateLogTable",
"ResourceType": "Custom::CreateLogTable",
"ResourceProperties": {
"S3DataLocations": [
"s3://loggingbucket/data/ApplicationLogs/",
"s3://loggingbucket/data/ApplicationLogs/",
"s3://loggingbucket/data/ApplicationLogs/",
"s3://loggingbucket/data/ApplicationLogs/"
]
}
}
And when NOT working:
...
{
"RequestType": "Create",
"ServiceToken": "hidden",
"ResponseURL": "hidden",
"StackId": "hidden",
"RequestId": "hidden",
"LogicalResourceId": "CreateLogTable",
"ResourceType": "Custom::CreateLogTable",
"ResourceProperties": {
"S3DataLocations": [
"s3://logging/data/ApplicationLogs/",
" s3://loggingbucket/data/ApplicationLogs/",
" s3://loggingbucket/data/ApplicationLogs/",
" s3://loggingbucket/data/ApplicationLogs/"
]
}
}
I'm a little stuck here, I think there might be some Type mismatch but I cant tell the difference between the manual and param.
Does anyone have any idea?

Answer 1

You can break your string into multiple line while preventing the change of \n into space using quotation and slash combo.
To verify that, I used the following surrogate template for your situation:
Resources:
MyBucket:
Type: AWS::S3::Bucket
Properties: {}
Outputs:
Test1:
Value: !Sub
- s3://${LoggingBucket}/data/ApplicationLogs1/,
s3://${LoggingBucket}/data/ApplicationLogs2/,
s3://${LoggingBucket}/data/ApplicationLogs3/
- { LoggingBucket: "Parent-LoggingBucket"}
Test2:
Value: !Sub
- "s3://${LoggingBucket}/data/ApplicationLogs1/,\
s3://${LoggingBucket}/data/ApplicationLogs2/,\
s3://${LoggingBucket}/data/ApplicationLogs3/"
- { LoggingBucket: "Parent-LoggingBucket"}
The Test1 produces string with spaces as in your question:
s3://Parent-LoggingBucket/data/ApplicationLogs1/, s3://Parent-LoggingBucket/data/ApplicationLogs2/, s3://Parent-LoggingBucket/data/ApplicationLogs3/
In contrast, Test2 does not have space:
s3://Parent-LoggingBucket/data/ApplicationLogs1/,s3://Parent-LoggingBucket/data/ApplicationLogs2/,s3://Parent-LoggingBucket/data/ApplicationLogs3/