Proposal: Template values files

[sstarcher]

To limit the need to duplicate values it would be helpful to be able to template the values files.

[osterman]

Also, just want to throw this out there: https://github.com/hairyhenderson/gomplate

gomplate > sprig

richer library of functions. pretty much everything sprig can do, but more! =)

[mumoshu]

@osterman Thx for the info! gomplate looks promising :)

Just to sync up with you, it looks like there is a momentum to let helmfile be close to helm's spec/behavior.
sprig sounded a good idea at the time we introduced it in that regard, but practically saying there can be more options.

That being said, I'm eager to providing options to use an alternative template engine like gomplate as long as it doesn't lock helmfile to single template engine, and the implementation is not so hard.

Actually, I prefer jsonnet as suggested in #92 here but it is attracted to no one 🤣

WDYT? Any input is welcomed!

[sstarcher]

Overall I would tend to stick with sprig unless we supported both.

[mumoshu]

@sstarcher I was considering to support this simply like:

releases:
- name: myrelease
   values:
   - myvalues.yaml

This configuration would just instruct helmfile to render a temporary yaml file from ./myvalues.yaml. The extension can be anything. So, even if it is .yaml, it's considered a sprig template. To be extra clear, it can be a standard yaml if the yaml doesn't include any golang text/template expressions in it.

Alternatives to the above is:

releases:
- name: myrelease
   values:
   - template: myvalues.yaml.tmpl

releases:
- name: myrelease
   valuesTemplates:
   - myvalues.yaml.tmpl

This looks more explicit which I personally prefer, but I guess the momentum in helmfile community is not make it too explicit like that, similar to helm's own template(no .tmpl extension, no distinction between template vs regular yaml file). In short, keeping it simple at glance seems like the way to go.

WDYT?

[sstarcher]

I would transparently support it s in your first example. Run the templates across all values files.

[mumoshu]

@sstarcher Thx. Sounds good. I've posted an enhanced example in #119 (comment).

[mumoshu]

Just submitted #216 for this