(custom_resources): How to break a cross-stack dependency

[pb8o]

Describe the bug

Hi, I have 2 stacks where one depends on the custom resource function of another.

Stack A has this

const myProvider = new cr.Provider(this, 'MyProvider', {onEventHandler: myFn});

It has an output like (edited):

MyStack:ExportsOutputFnGetAttMyProviderframeworkonEvent60E6A034ArnCBF1E63C

Stack B gets passed myProvider as a parameter and has this

myCR = new core.CustomResource(this, 'Sync', {
            serviceToken: myProvider.serviceToken,
            properties: {...}
}

I am now trying to break the relationship between the two, but it I am blocked since there is no direct access to the CDK-generated Lambda.

Expected Behavior

this.exportValue(myProvider);

Current Behavior

Error: exportValue: either supply 'name' or make sure to export a resource attribute (like 'bucket.bucketName')

Reproduction Steps

const myProvider = new cr.Provider(this, 'MyProvider', {onEventHandler: myFn});

Possible Solution

Would it be as easy as exposing this as a property of Provider?

https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/custom-resources/lib/provider-framework/provider.ts#L181

Additional Information/Context

No response

CDK CLI Version

2.89.0

Framework Version

No response

Node.js Version

18

OS

Linux

Language

Typescript

Language Version

No response

Other information

No response

[pahud]

It's not clear to me where the error comes from.

Error: exportValue: either supply 'name' or make sure to export a resource attribute (like 'bucket.bucketName')

Do you mean the myProvider is in stack A but myFn is in stack B?

const myProvider = new cr.Provider(this, 'MyProvider', {onEventHandler: myFn});

Can you share the smallest code that represents both stacks and the their content?

[pb8o]

Ok I updated the details of the issue. Sorry it is not very clear where the dependency is coming from. This is code I want to simplify.

Any help with a workaround would be very appreciated.

[pb8o]

Ok I made some tiny progress. This is what I am trying to write for breaking the dependency:

        // to break the dependency, for the transition
        const ltSyncerFn = new lambda.Function(this, 'Sync Launch Template', {
            memorySize: 128, // MB
            timeout: core.Duration.seconds(60),
            runtime: lambda.Runtime.NODEJS_18_X,
            code: new lambda.InlineCode('foo'),
            handler: 'index.handler',
        });
        const ltSyncProvider = new cr.Provider(this, 'LaunchTemplateSyncProvider', {
            onEventHandler: ltSyncerFn,
        });
        this.exportValue(ltSyncProvider.entrypoint);

and this is what I get:

lib/imageBuilder.ts:196:41 - error TS2341: Property 'entrypoint' is private and only accessible within class 'Provider'.

196         this.exportValue(ltSyncProvider.entrypoint);
                                            ~~~~~~~~~~

Would it make sense to make that property public, so we can keep exporting it?

[pahud]

const ltSyncProvider = new cr.Provider(this, 'LaunchTemplateSyncProvider', {
            onEventHandler: ltSyncerFn,
        });
        this.exportValue(ltSyncProvider.entrypoint);

Why would you export the entrypoint?

It is actually private so you can't export it like that.

aws-cdk/packages/aws-cdk-lib/custom-resources/lib/provider-framework/provider.ts

Line 154 in 2855da6

private readonly entrypoint: lambda.Function;

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