(pipelines): Cannot deploy a cross-region pipeline from a Stage

[gshpychka]

What is the problem?

The cross-region support stack created by CDK pipeline is placed in the wrong scope - outside of the Stage, which leads to dependency crossing a stage boundary error on synth.

This makes it impossible to deploy a cross-region CDK pipeline from a Stage.

Reproduction Steps

from aws_cdk import core as cdk, pipelines, aws_ec2 as ec2
import os


class MyStage(cdk.Stage):
    def __init__(
        self,
        scope: cdk.Construct,
        id: str,
        **kwargs,
    ) -> None:
        super().__init__(scope, id, **kwargs)
        Pipeline(self, "Pipeline")


class Pipeline(cdk.Stack):
    def __init__(
        self,
        scope: cdk.Construct,
        id: str,
        **kwargs,
    ) -> None:
        super().__init__(scope, id, **kwargs)

        source = pipelines.CodePipelineSource.connection(
            repo_string="owner/repo",
            branch="",
            connection_arn="my_arn",
        )

        synth_step = pipelines.ShellStep(
            "synth",
            commands=[],
            input=source,
        )

        pipeline = pipelines.CodePipeline(
            self,
            "pipeline",
            synth=synth_step,
        )

        pipeline.add_stage(
            MultiRegion(self, "main", env=cdk.Environment(region="ap-northeast-1"))
        )


class MultiRegion(cdk.Stage):
    def __init__(
        self,
        scope: cdk.Construct,
        id: str,
        **kwargs,
    ) -> None:
        super().__init__(scope, id, **kwargs)
        AppStack(self, "app")


class AppStack(cdk.Stack):
    def __init__(
        self,
        scope: cdk.Construct,
        id: str,
        **kwargs,
    ) -> None:
        super().__init__(scope, id, **kwargs)
        ec2.Vpc(self, "vpc")


if __name__ == "__main__":
    env = cdk.Environment(account=os.environ["CDK_DEFAULT_ACCOUNT"], region="eu-west-1")
    app = cdk.App()
    MyStage(app, "Stage", env=env)
    app.synth()

cdk synth

What did you expect to happen?

Successful synth

What actually happened?

jsii.errors.JSIIError: You cannot add a dependency from 'Stage/Pipeline' (in Stage 'Stage') to 'cross-region-stack-<account_id>:ap-northeast-1' (in the App): dependency cannot cross stage boundaries

CDK CLI Version

1.133.0

Framework Version

No response

Node.js Version

17.1.0

OS

Linux

Language

Typescript, Python, .NET, Java, Go

Language Version

No response

Other information

No response

[gshpychka]

From my understanding after discussing with @rix0rrr , it seems that the issue is in here:

aws-cdk/packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts

Line 627 in 279c4be

supportStack = new CrossRegionSupportStack(app, supportStackId, {

[rix0rrr]

Yep. app needs to be this.

[github-actions]

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