aws-cdk.aws_events: Resolution error: Supplied properties not correct for "CfnEventBusProps"

[ashleydaley]

What is the problem?

After pip install aws-cdk 1.129.0, when creating a Stack that contains an aws_events.EventBus that does not have (optional) event_bus_name defined errors with the following message when we cdk synth the app:

jsii.errors.JavaScriptError: 
  Error: Resolution error: Supplied properties not correct for "CfnEventBusProps"
    name: required but missing.
      at ValidationResult.assertSuccess (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/runtime.js:139:19)
      at cfnEventBusPropsToCloudFormation (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/aws-events/lib/events.generated.js:476:43)
      at CfnEventBus.renderProperties (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/aws-events/lib/events.generated.js:560:16)
      at PostResolveToken.ret.Resources [as processor] (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/cfn-resource.js:303:52)
      at PostResolveToken.postProcess (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/util.js:81:21)
      at Object.postProcess (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:59:82)
      at DefaultTokenResolver.resolveToken (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/resolvable.js:59:38)
      at resolve (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:130:55)
      at Object.resolve (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:57:48)
      at resolve (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:145:51)

After downgrading python module to aws-cdk 1.128.0, the same error does not occur and stack is built successfully

Reproduction Steps

import os
from aws_cdk import core, aws_events

env = core.Environment(region=os.environ["AWS_DEFAULT_REGION"], account=os.environ["AWS_ACCOUNT_ID"])


class TestStack(core.Stack):
    def __init__(
        self,
        scope: core.Construct,
        id: str,
        **kwargs,
    ):
        core.Stack.__init__(self, scope, id, **kwargs)
        aws_events.EventBus(self, "event_bus")


app = core.App()
test_stack = TestStack(app, "test-stack", env=env)
app.synth()

What did you expect to happen?

The stack should synth and build normally, and an auto-generated event_bus_name should be created

What actually happened?

The synth failed with

jsii.errors.JavaScriptError: 
  Error: Resolution error: Supplied properties not correct for "CfnEventBusProps"
    name: required but missing.
      at ValidationResult.assertSuccess (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/runtime.js:139:19)
      at cfnEventBusPropsToCloudFormation (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/aws-events/lib/events.generated.js:476:43)
      at CfnEventBus.renderProperties (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/aws-events/lib/events.generated.js:560:16)
      at PostResolveToken.ret.Resources [as processor] (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/cfn-resource.js:303:52)
      at PostResolveToken.postProcess (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/util.js:81:21)
      at Object.postProcess (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:59:82)
      at DefaultTokenResolver.resolveToken (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/resolvable.js:59:38)
      at resolve (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:130:55)
      at Object.resolve (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:57:48)
      at resolve (/tmp/jsii-kernel-RpWQUL/node_modules/@aws-cdk/core/lib/private/resolve.js:145:51)

CDK CLI Version

1.129.0 (build fb43f89)

Framework Version

No response

Node.js Version

14.7.5

OS

Amazon Linux 2

Language

Python

Language Version

3.8.8

Other information

No response

[ashleydaley]

Setting an event_bus_name allows a successful build, but cdk docs state this to be optional

[rix0rrr]

It's unfortunate that the docs state the parameter is optional, as CloudFormation really states this is required:

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-events-eventbus.html#cfn-events-eventbus-name

I guess the only thing to do is to invent a name on-the-fly, as we do for other constructs (like cloudwatch.Dashboard).

[gavllew]

I think this had something to do with fix #17008 for issue #14337. Until then, CDK was already inventing a name on-the-fly.

[jasonwadsworth]

As a work around I ended up setting the name using the name that was generated in previous versions of the CDK.

[github-actions]

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