POC: Add sprig library

[angrycub]

This PR adds the Sprig template functions library. For clarity and ease of documentation, the sprig functions are renamed sprig_«function».

[angrycub]

Here is a template that I used to experiment with Sprig (list, append, and sprig's join renamed as sprig_join)

{{- $service := service "nomad" -}}
{{- scratch.Set "acc" sprig_list -}}
{{- range $service -}}
  {{- $curAcc := scratch.Get "acc" -}}
  {{- scratch.Set "acc" (sprig_append $curAcc (printf "%s:%v" .Address .Port) ) -}}
{{- end -}}
{{- scratch.Get "acc" | sprig_join "," }}

[eikenb]

Hey @angrycub, thanks for taking the time to submit a PR.

I hadn't heard of the sprig library but this definitely looks like it could be useful. I'm not going to put this in the upcoming release (0.25.0) that I'm preparing for as this will take a bit of time to research and I'm not sure how to handle documentation for it (plus I really want to rework the documentation into a better format first).

[freeseacher]

Can't wait to see it being merged!

[eikenb]

@freeseacher .. Thanks for the interest. Be sure to 👍 the PR (top post) to vote for this. We use the 👍's as a way to judge community priority. Thanks.

[vbatuev]

It's very useful feature. Thank you!

[angrycub]

@eikenb - I was looking at this as I was rebasing it last, and I was thinking. What about if we decorate all of the sprig functions so that you could say that we provide them as sprig_* , rather than merging them into the top level, and then provided a sprig_version function so that someone could determine what version of sprig was compiled into the library? That would help simplify the documentation.

[eikenb]

@angrycub... I'm back! I like the idea of prefixing the functions to make it an obvious namespace. If you're still interested, please update the PR with your idea. Thanks!

[eikenb]

@angrycub, if you update this would you please consider adding at least a small/stub update to the documentation. Just a short something about the sprig project/library and a link to its documentation would be great. Thanks!

[eikenb]

Note to self. I spoke with @angrycub via slack (didn't notice they were another hashi employee) and he wants to look into another way of organizing it (inspired by hugo's template setup) and will re-submit.

[hashicorp-cla]

All committers have signed the CLA.

[cucxabong]

any update on this

[eikenb]

@angrycub .. were you still thinking about reworking your approach for this feature/PR?

[Chinikins]

is there an update on this, it would be super useful

[bitsofinfo]

would love this!

[eikenb]

I'll add this to the 0.28.0 milestone and look at it for that release.

[angrycub]

I looked into namespacing the sprig funcs, and it's (kind of) possible, but you end up having to upcase the first letter of the sprig function name so that they are exported funcs on a returned object. It's not the ugliest thing I've ever seen, but it does push it a little further away from the documented names--and seems to provide no real bonus usability compared to just whacking sprig_ in front of the func names.

I can get this PR back into shape prepending sprig_ if you'd like, or we can have a quick convo about the namespacing attempts.

[angrycub]

I updated the early version PR comments to reflect the current truth of the PR (prefixes and for all the funcs and the sample template using the funcs) as well

[eikenb]

👍 LGTM

Thanks!

[eikenb]

[ninja edit: fixed referenced bug #]

Fixes #1206

Seeing if that will auto-close the ticket. Not sure if comments trigger that.

[Chinikins]

thanks for the quick update!