Duplicated synthed resources when nesting Charts

[benagricola]

Description of the bug:

When nesting charts within a parent chart, applying the parent chart to an app and then synthesizing the app, I'm seeing duplicated synthed resources - one file for each separate chart nested in the parent chart, and then one file for the parent chart which also includes the resources from the nested charts.

This is problematic when applying to Kubernetes using kubectl apply -f dist/ as the files contain duplicate identically named resources. Not sure if this is expected or not but submitting as a bug report just in case 🙂

Reproduction Steps:

app/test.ts:

import { App, Chart } from 'cdk8s'
import { Construct } from 'constructs'
import { Namespace } from '../imports/k8s';


export class ChildChart1 extends Chart {
    constructor(scope: Construct, name: string) {
      super(scope, name)
      const ns1 = new Namespace(this, 'namespace1')
    }
}

export class ChildChart2 extends Chart {
    constructor(scope: Construct, name: string) {
      super(scope, name)
      const ns2 = new Namespace(this, 'namespace2')
    }
}

export class ParentChart extends Chart {
    constructor(scope: Construct, name: string) {
        super(scope, name)
        const childChart1 = new ChildChart1(this, 'child1')
        const childChart2 = new ChildChart2(this, 'child2')
        const ns3 = new Namespace(this, 'namespace3')
    }
}
const app = new App()
const parent = new ParentChart(app, 'parent')
app.synth()

shell:

➜  cdk8s git:(feat/nested-children) ✗ cdk8s synth -a "npx ts-node -r tsconfig-paths/register app/test.ts"
dist/parent-child1-cad88a69.k8s.yaml
dist/parent-child2-1e516eb8.k8s.yaml
dist/parent.k8s.yaml

➜  cdk8s git:(feat/nested-children) ✗ cat dist/parent-child1-cad88a69.k8s.yaml
apiVersion: "v1"
kind: "Namespace"
metadata:
  name: "parent-child1-namespace1-e27612e5"

➜  cdk8s git:(feat/nested-children) ✗ cat dist/parent-child2-1e516eb8.k8s.yaml
apiVersion: "v1"
kind: "Namespace"
metadata:
  name: "parent-child2-namespace2-32aecabe"

➜  cdk8s git:(feat/nested-children) ✗ cat dist/parent.k8s.yaml
apiVersion: "v1"
kind: "Namespace"
metadata:
  name: "parent-child1-namespace1-e27612e5"
---
apiVersion: "v1"
kind: "Namespace"
metadata:
  name: "parent-child2-namespace2-32aecabe"
---
apiVersion: "v1"
kind: "Namespace"
metadata:
  name: "parent-namespace3-7362c69c"

Environment:

cdk8s-test@0.0.1 
├── @types/jest@26.0.15
├── @types/node@14.14.6
├── cdk8s@0.33.0
├── cdk8s-cli@0.33.0
├── cdk8s-plus@0.33.0
├── constructs@3.2.11
├── dotenv@8.2.0
├── jest@26.6.3
├── npm-run-all@4.1.5
├── source-map@0.7.3
├── source-map-support@0.5.19
├── ts-jest@26.4.3
├── ts-node@9.0.0
├── tsconfig-paths@3.9.0
└── typescript@4.0.5

Other:

I'm not bothered what the correct output is here. It seems to me that output should either be in individual files (one per nested child, with the parent resources in their own file) or all resources should be put into the one parent file. I don't think it matters, as long as the directory itself doesn't contain duplicate resources.

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This is 🐛 Bug Report