fix(util): correct logging for synth

[iceglober]

FYI - This is my first OSS contribution. I'm open to any feedback or input!

Summary of Changes

The console logs generated during cdk8s synth gave the impression that synthesis had failed when it actually succeeded, leading to unnecessary confusion. This change updates that log to a warning if the outdir doesn't exist, and also adds a "success" log if generated manifests are found. This isn't actually a problem because synth in cdk8s-core always attempts to create the necessary directory.

Current State

Without providing a CLI option for outdir and without specifying an outdir property in my config file, I defined my App like so:

const app = new App({
    outdir: 'out',
    yamlOutputType: YamlOutputType.FOLDER_PER_CHART_FILE_PER_RESOURCE,
});
new MongoDbChart(app, 'mongoDb2');
app.synth();

where outdir is defined in my IaC directly. I wanted to make a clear differentiation between TS output ("dist") and cdk8s output (I chose "out").

With this current state, here's what the console output looks like:

iceglobe@iceglobe-MS-7C79 ~/projects/kayn/k8s/cdk8s
 % cdk8s synth
Synthesizing application
ERROR: synthesis failed, app expected to create "dist"

This "ERROR" message gives the false impression that manifest synthesis failed, when in reality, because I had specified a different outdir in my TS file, everything worked just fine.

Proposed Change

My changes make it so that the console output reflects the following:

iceglobe@iceglobe-MS-7C79 ~/projects/kayn/k8s/cdk8s
 % cdk8s synth
WARNING: specified outdir does not exist, synth command could fail
Synthesizing application
  - dist/mongodb2-c84b3744/Deployment.mongodb.k8s.yaml
  - dist/mongodb2-c84b3744/Secret.mongodb-secret.k8s.yaml
  - dist/mongodb2-c84b3744/Service.mongodb-service.k8s.yaml
Manifests synthesized!

This accomplishes the following:

• Gives warning that synth might fail depending on the shell command that is run
• Allows intended logging of generated manifests to be displayed (this was previously inhibited because the pathExists check resulted in an exit)
• Gives an affirmative message that manifests were indeed generated as expected ("Manifests synthesized!")

[iliapolo]

@iceglober Appreciate the work here, but we can't accept this change because it inherently changes the behavior of the CLI. Also as I explain in the comments, the current behavior is the desired one, albeit somewhat confusing.

Thanks!

[iliapolo]

Putting this here means that this warning will always be printed because the outdir is expected to be created further down (in the await shell call).

[iliapolo]

I don't think this necessary though. If we found manifests, then we print their path already, indicating a successful synthesis.

[iliapolo]

I understand where your coming from with having synth not fail in this case (because manifests were actually created). However, from the CLIs perspective, synthesis is not only creating manifests, there are additional CLI features (like validations) that rely on the fact this directory exists, and so from its POV, synthesis is not successful. This does unfortunately mean that, if you define outdir in your app, you must also change the output property in the cdk8s.yaml configuration file.

Note that if you do it the other way around, i.e set output: out in cdk8s.yaml, and leave the App instance with its defaults, everything will work as expected.

[iliapolo]

Apologies for the long delay in reviewing this.