Reusing fieldSpecs accross transformers in overlays

[artur-jablonski]

i have the following directory structure:

root/
├─ base/
│  ├─ kustomization.yaml
├─ overlays/
│  ├─ development/
│  │  ├─ transformers/
│  │  │  ├─ envSuffixer.yaml
│  │  ├─ kustomization.yaml
│  ├─ acceptance/
│  │  ├─ transformers/
│  │  │  ├─ envSuffixer.yaml
│  │  ├─ kustomization.yaml

root/overlays/development/transformers/envSuffixer.yaml and
root/overlays/acceptance/transformers/envSuffixer.yaml are almost identical:

apiVersion: builtin
kind: PrefixSuffixTransformer
metadata:
  name: envSuffixer
suffix: xxx # <--- that's the only different part
fieldSpecs:
  - kind: Kind1
    path: path1
  - kind: Kind1
    path: path2
  - kind: Kind1
    path: path3
  - kind: Kind2
    path: path1
  - kind: Kind2
    path: path2

Is there any way I can get rid of the duplication between those transfomers? Can I somehow reuse at least the fieldSpecs? Or structure things differently so that this reuse is possible?

[artur-jablonski]

Ok, so I ended up with somehow hacky way to do this.

The basic idea is to have a separate kustomize build for the transformers that fed into the main kustomize build. Let me explain:

.
└── root/
    ├── base/
    │   ├── ...
    │   └── kustomization.yaml
    └── overlays/
        ├── developement/
        │   ├── transformers/
        │   └── kustomization.yaml
        ├── acceptance/
        │   ├── transformers/
        │   └── kustomization.yaml
        └── transformers/
            ├── base/
            │   ├── envSuffixer.yaml
            │   └── kustomization.yaml
            └── overlays/
                ├── developement/
                │   ├── envSuffixer.yaml
                │   └── kustomization.yaml
                └── acceptance/
                    ├── envSuffixer.yaml
                    └── kustomization.yaml

in root/overlays/transformers/base/envSuffixer.yaml I have the common part of the transformer:

apiVersion: builtin
kind: PrefixSuffixTransformer
metadata:
  name: envSuffixer
fieldSpecs:
  - kind: Kind1
    path: path1
  - kind: Kind1
    path: path2
  - kind: Kind1
    path: path3
  - kind: Kind2
    path: path1
  - kind: Kind2
    path: path2

and in the overlays patch like root/overlays/transformers/overlays/development/enfSuffixer.yaml only the dev specific part:

kind: PrefixSuffixTransformer
metadata:
  name: envSuffixer
suffix: development

So now when I need to generate the yamls I need to do it in two steps.

First generate transformers for given overlay:

kubectl kustomize root/overlays/transformers/overlays/developement > root/overlays/developement/transformers/transformers.yaml

Second generate the actual yamls

kubectl kustomize root/overlays/developement

Hacky, but it works and avoids duplication in the transformers.

Feels like it should be better way of doing this.....