Received ''null' values are not allowed in templates'' while creating AWS::Events::Rule -> EventPattern

[rohan-1995]

Name of the resource

AWS::Events::Rule

Resource Name

No response

Issue Description

EventPattern accepts Null value as per EventBridge service [1] ,even CDK documentation [2] mention that EventPattern can have null values. However CloudFormation service does not accept Null value when defined for EventPattern. Template fails in validation with following error - 'null' values are not allowed in templates

[1] https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-event-patterns-null-values.html
[2] https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_events.EventPattern.html

Expected Behavior

AWS::Events::Rule should accept null values for 'EventPattern' property

Observed Behavior

template does not pass validation and throws error - 'null' values are not allowed in templates

Test Cases

Create EventBridge rule with EventPattern having null value in CFN template

Other Details

No response

[minne6]

Hi,
Do you have any solution for this problem? Is this fixed? I am unable to use null check in eventbridge pattern using yaml cloudformation template.
@rohan-1995

[slootjes]

Almost 2 years later, this is still an issue.

[slootjes]

My colleague had a brilliant hacky idea and it seems to work. Since the property EventPattern is a JSON type, it also supports a stringified JSON object, where null values are allowed.

YourRule:
  Type: AWS::Events::Rule
  Properties:
      EventPattern: '{
		  "detail": {
			 "responseElements": [null]
		  }
		}'

It doesn't look pretty but it does the trick :)