CDK Code Pipeline Lambda deployment is deleting old versions with removal policy set to RETAIN

After following the guide for a Lambda deploying pipeline, I eventually got a running build. I can commit a change to codecommit which will kick off the pipeline. The specified alias will be moved (or created) and point to the new version. But the old version and any alias attached to it will be deleted. I am always left with two versions ($LATEST and the just-deployed one) and one alias (the just-deployed one).

What I expected to happen in the case of a commit that does not change the alias:

• The alias is updated to point to the new version and the old version is not deleted

What I expected to happen in the case of a commit that did change the alias:

• The previous alias(es) points to whatever version they were pointing to before
• The new alias points to the new version and any old versions are not deleted

Reproduction Steps

1. Follow this guide
2. Change the FunctionProps.currentVersionOptions.removalPolicy to RETAIN. (this actually does not appear to matter)
3. Change the name of the alias and commit.
4. The deployment deletes the previous version and alias and sets the new alias to the new version.

    this.lambdaCode = Lambda.Code.fromCfnParameters();
    const lambdaFnProps: Lambda.FunctionProps = {
      handler: "index.handler",
      code: this.lambdaCode,
      runtime: Lambda.Runtime.NODEJS_12_X,
      description: "description",
      role: role,
      functionName: this.lambdaFnName,
      currentVersionOptions: {
        removalPolicy: RemovalPolicy.RETAIN
      }
    };

    const func = new Lambda.Function(this, "LambdaFunction", lambdaFnProps);
    const version = func.addVersion(new Date().toISOString());
    const alias = new Lambda.Alias(this, 'LambdaAlias', {
      aliasName: 'dev2',
      version,
    });

    const deploy = new CodeDeploy.LambdaDeploymentGroup(this, "LambdaDeploymentGroup", {
      alias: alias,
      deploymentConfig: CodeDeploy.LambdaDeploymentConfig.ALL_AT_ONCE,
    });

CDK Diff Output

The output from running cdk diff pretty much shows what ends up happening:

Resources
[-] AWS::Lambda::Version LambdaFunctionVersion20200428T062510953Z1CA2012F destroy
[-] AWS::Lambda::Alias LambdaFunctionVersion20200428T062510953ZAliasdev26C46D216 destroy
[+] AWS::Lambda::Version LambdaFunction/Version2020-04-28T06:39:18.760Z LambdaFunctionVersion20200428T063918760Z149463F3 
[+] AWS::Lambda::Alias LambdaFunction/Version2020-04-28T06:39:18.760Z/Aliasdev2 LambdaFunctionVersion20200428T063918760ZAliasdev282DEF3AB 

Error Log

Environment

• CDK Version: 1.35
• OS: Mac
• Language : Typescript

Other

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This is 🐛 Bug Report

[hoegertn]

I am retaining old versions like this: https://github.com/taimos/cdk-construct-alexa-skill/blob/master/lib/alexa-stack.ts#L71

[zachbarrow]

@skinny85 I did some testing and your suggestions worked. Thanks for the help. Thanks also @hoegertn for the code example.