¬ just serendipity 🍀 (not just serendipity)

Helm charts support the inclusion of a values.schema.json file to validate values.yaml. Documentation: https://helm.sh/docs/topics/charts/#schema-files

A JSON schema is akin to defining the structure of and type-annotating a JSON file. It helps to “shift left” the lifecycle of your helm releases.

For a pre-existing values.yaml file, it may be quite tedious to generate the schema from scratch, by hand.

Can we automate this process?

Of course we can.

One possibility is to use GenAI / LLMs. This is out of scope of this post.

Another possibility is to leverage a helm plug-in to do so.

I had a good experience with https://github.com/karuppiah7890/helm-schema-gen:

helm plugin install https://github.com/karuppiah7890/helm-schema-gen.git
cd path/to/helm/chart
helm schema-gen values.yaml | tee values.schema.json

Afterwards, test the generated schema with:

helm lint path/to/helm/chart

Usually I need to do some follow-up edits to the generated file, including:

• add string enum types for a tighter validation of strings
• mark certain fields as required
• mark certain fields with additionalProperties: "false"
• augment ["null"] to ["null", "string"] for keys that do not have a default value

It’s worth to observe that, at the time of this publication, the following notice is present in the repository of the plug-in:

This repository has been archived by the owner on Aug 31, 2021. It is now read-only.

Nonetheless, it still works well.