[cdk-pipelines] CDK Pipeline Application deployment stage uses backslashes for Template URL on Windows

[Pettles]

Adding an application deployment stage to a CDK Pipeline from Windows uses a backslash separator in the Template URL of the CloudFormation CHANGE_SET_REPLACE step, resulting in an 'Action Execution Failure'.

Reproduction Steps

Deployed a CDK Pipeline Stack with the following code:

class MySourceStack(cdk.Stack):
    def __init__(self, scope: cdk.Construct, id: str, **kwargs) -> None:
        super().__init__(scope, id, **kwargs)
        code_commit_role = iam.Role(self, 'CodeCommitRole', assumed_by=iam.AccountRootPrincipal())


class MyStage(cdk.Stage):
    def __init__(self, scope: cdk.Construct, id: str, **kwargs):
        super().__init__(scope, id, **kwargs)
        MySourceStack(self, 'IAMRole')


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

        source_artifact = codepipeline.Artifact()
        cloud_assembly_artifact = codepipeline.Artifact()

        source_repository = codecommit.Repository.from_repository_arn(
            self, 'Source_Repository',
            # .. Source Repo
        )

        # Create the Pipeline with the Source and Synth actions
        pipeline = CdkPipeline(self, "Pipeline",
            cloud_assembly_artifact=cloud_assembly_artifact,
            source_action=codepipeline_actions.CodeCommitSourceAction(
                action_name='CodeCommit',
                output=source_artifact,
                repository=source_repository,
                branch='master'
            ),
            synth_action=SimpleSynthAction(
                source_artifact=source_artifact,
                cloud_assembly_artifact=cloud_assembly_artifact,
                # Does installation and build for python
                install_commands=["npm install -g aws-cdk"],
                build_commands=["pip install -r requirements.txt"],
                synth_command="cdk synth"
            ),
        )
        # Create the Application deployment actions
        pipeline.add_application_stage(MyStage(self, 'PreProd'))

Upon running the pipeline, the execution fails at the 'PreProd' CloudFormation CHANGE_SET_REPLACE action with the error:

Action execution failed
File [assembly-myproject-PreProd\myprojectPreProdIAMRole470A8317.template.json] does not exist in artifact [Artifact_Build_Synth]

Manually editing the Pipeline CHANGE_SET_REPLACE action and changing the backslash in the template URL to a forward slash allows the pipeline to execute successfully.

What did you expect to happen?

CDK Pipeline deployment to use forward-slashes in order to join directory names when creating the template URL to provide to the CHANGE_SET_REPLACE action.

What actually happened?

The Template URL provided to the CHANGE_SET_REPLACE step used backslashes to join the directory names, resulting in an error.

Environment

• CDK CLI Version : 1.72.0 (build c2f38e8)
• Framework Version: 1.72.0
• Node.js Version: v12.19.0
• OS : Windows 10
• Language (Version): Python 3.8.6

Other

Deployed using PowerShell as a Terminal from PyCharm.

---

This is 🐛 Bug Report

[Pettles]

Hey team,
I assume the root cause of this issue is similar to that identified in: #11359

[Pettles]

Hey team,
Testing this further, I've found a simple workaround is to enable self_mutation on the CDK Pipeline, as this detects the change in the Template URL created by the synth action, and updates the pipeline to resolve the issue itself.
It does still mean that the initial deployment, and any deployment with self mutation disabled, is still encountering this issue.

[github-actions]

⚠️COMMENT VISIBILITY WARNING⚠️

Comments on closed issues are hard for our team to see.
If you need more assistance, please either tag a team member or open a new issue that references this one.
If you wish to keep having a conversation with other community members under this issue feel free to do so.