modifying cue with cue commands (aka workflows)?

[nfi-hashicorp]

I'm working through the Github Actions example, fiddling around with Cue. I imported the YAML successfully and am round-tripping fine.

I introduced a shared db of external actions and their versions so that I can centralize that version info, similar to a go.mod file. I was hoping to change my Cue source programatically to use this new construct by writing a new cue command (aka workflow aka tool) that changes the Cue source itself. But alas, there does not appear to be any functionality to do so? e.g., an encoding/cue package.

Yes, I'm sure it could be done with the Go API, but seems like a missed opportunity.

[myitcv]

Hi @nfi-hashicorp - #1852 tracks adding a encoding/cue standard library package. However if you are usingthecue` CLI then you might not need that package.

I was hoping to change my Cue source programatically to use this new construct by writing a new cue command (aka workflow aka tool) that changes the Cue source itself.

This should be possible by writing a workflow that use tool/exec to wrap cmd/cue.

Please can you post a bit more detail about the kind of transformation you're looking to perform?

We can then see whether such a "wrapper" will meet your needs.

[nfi-hashicorp]

Ok, for example, I've extracted all actions versions into this:

let actions_lock = {
  "actions/cache": "0c45773b623bea8c8e75f6c82b208c3cf94ea4f9"
  "actions/checkout": "a5ac7e51b41094c92402da3b24376905380afc29"
  "actions/github-script": "60a0d83039c74a4aee543508d2ffcb1c3799cdea"
  ...
}

And I'd like to programmatically replace all instances of

workflows: [_]: jobs: [_]: steps: [
  {uses: "actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9", ...}
]

(pseudo-code)

with

workflows: [_]: jobs: [_]: steps: [
  {uses: "actions/cache@\(actions_lock.["actions/cache"])", ...}
]

Yes, that's something I could do with sed, but I'd prefer structured editing.

Really, I'd prefer to do something like the function pattern:

#UseAction: {
	_uses: string // TODO: must be key in actions_lock
	uses: "\(_uses)@\(actions_lock[_uses])"
	...
}

workflows: [_]: jobs: [_]: steps: [
  #UseAction & {_uses: "actions/cache"}
]

Extra super bonus points if encoding/cue can work on a deeper syntactical level and retain comments, style, and structure!

[myitcv]

Apologies for the delay in replying here. Busy week! I will reply asap.

[myitcv]

Hi @nfi-hashicorp - apologies for the super long delay in replying here. We've been super busy with evalv3 and curated-modules related work. Appreciate the patience here.

Indeed, it's because of the combined efforts of that work that I'm now able to present a response to you that uses the work-in-progress curated modules:

# This only works with evalv3 - this will become the default soon
# Following https://cuelang.org/issue/3662.
env CUE_EXPERIMENT=evalv3=1
env CUE_DEBUG=openinline=0

# Pre-amble
exec cue mod tidy

# Export
exec cue export --out yaml
cmp stdout stdout.golden

-- cue.mod/module.cue --
module: "mod.example"
language: {
	version: "v0.13.0"
}
deps: {
	"github.com/cue-tmp/jsonschema-pub/exp3/githubactions@v0": {
		v: "v0.2.0"
	}
}
-- x.cue --
package workflow

import (
	"github.com/cue-tmp/jsonschema-pub/exp3/githubactions"
)

// Define our actions lock
let actions_lock = {
	"actions/cache":         "0c45773b623bea8c8e75f6c82b208c3cf94ea4f9"
	"actions/checkout":      "a5ac7e51b41094c92402da3b24376905380afc29"
	"actions/github-script": "60a0d83039c74a4aee543508d2ffcb1c3799cdea"
}

// Build a derived definition based on the core #Workflow
#ourWorkflow: githubactions.#Workflow & {
	jobs?: [string]: steps?: [...{
		_uses?: string
		if _uses != _|_ {
			uses: "actions/cache@\(actions_lock[_uses])"
		}
	}]
}

// Use that definition
w1: #ourWorkflow & {
	on: push: {}
	jobs: test: steps: [...{
		_uses?: string
		if _uses != _|_ {
			uses: "actions/cache@\(actions_lock[_uses])"
		}
	}]

	jobs: test: {
		"runs-on": "ubuntu-24.04"

		steps: [
			{
				_uses: "actions/cache"
			},
		]
	}
}
-- stdout.golden --
w1:
  "on":
    push: {}
  jobs:
    test:
      steps:
        - uses: actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9
      runs-on: ubuntu-24.04

More than happy to jump onto a quick call to talk through what's going on here if that would help.