Adding another disjunction option while keeping all the existing ones from another definition

[ullarseerme]

I'm new to CUE and thus my terminology may be wrong, so apologies in advance!

What I'm trying to achieve is while using this version of the GitHub Actions workflow schema, is to augment the default elements for runs-on, which in CUE looks like the following:

// The type of machine to run the job on. The machine can be
// either a GitHub-hosted runner, or a self-hosted runner.
"runs-on": "macos-10.15" | "macos-11" | "macos-12" | "macos-latest" | "self-hosted" | "ubuntu-18.04" | "ubuntu-20.04" | "ubuntu-22.04" | "ubuntu-latest" | "windows-2019" | "windows-2022" | "windows-latest" | (["self-hosted", ...string] & [_, ...] | ["self-hosted", #machine, ...string] & [_, _, ...] | ["self-hosted", #architecture, ...string] & [_, _, ...] | ["self-hosted", #machine, #architecture, ...string] & [_, _, _, ...] | ["self-hosted", #architecture, #machine, ...string] & [_, _, _, ...]) & [...] | #stringContainingExpressionSyntax

The snippet above is from the CUE version of the schema (cue import -f -p github -l #Workflow: jsonschema: - -o -) in the file github-workflow.cue in the following directory structure:

$ tree
.
├── cue.mod
│   ├── module.cue
│   ├── pkg
│   │   └── json.schemastore.org
│   │       └── github
│   │           └── github-workflow.cue
│   └── usr
│       └── json.schemastore.org
│           └── github
│               └── workflow.cue
└── workflows.cue

Under workflows.cue (plural, top-level) I'm able to successfully do the following:

package workflows

import "json.schemastore.org/github"

#javaWorkflow: github.#Workflow & {
	jobs: [string]: "runs-on": "ubuntu-latest"
}

But what I'd want is to input an arbitrary string to be able to reference self-hosted runners. Looking at the schema I noticed that it's possible to just write ["self-hosted", "my-arbitrary-string"] and that would be fine, but when the workflow starts it gets stuck because there is no runner registered under "self-hosted". I could just register a new runner under that name, but I want to get better at CUE.

I'm looking for a way define an override for runs-on such that everything that is already defined under the schema will remain so, but that I am able to say that just "my-arbitrary-string" would also be okay to input. My workflow.cue (singular, nested under usr) looks like this:

package github

// TODO: drop when cuelang.org/issue/390 is fixed.
// Declare definitions for sub-schemas
#job:  ((#Workflow & {}).jobs & {x: _}).x
#step: ((#job & {steps:             _}).steps & [_])[0]

#NewNormalJob: #Workflow | *{
    jobs: #Workflow.#normalJob.jobs & {
        "runs-on": _ | "my-arbitrary-string"
    }
}

Ideally I'd love it if I didn't have to create a whole new definition (#NewNormalJob) and could just leverage the existing #Workflow definition, but that may be a pipe dream.

[jpluscplusm]

Just to check: you've read https://docs.github.com/en/actions/using-jobs/choosing-the-runner-for-a-job#choosing-self-hosted-runners, where it says:

Although the self-hosted label is not required, we strongly recommend specifying it when using self-hosted runners to ensure that your job does not unintentionally specify any current or future GitHub-hosted runners

... and your requirement is to allow the consumer to do what they don't recommend: to only specify a single label, without also specifying the self-hosted label? (It'll either be doable in CUE or not - I'm just checking I've correctly understood the requirement!)

[ullarseerme]

You'd be right in the usual scenario of self-hosting runners, but we are using GitHub ARC (sorry for not being more specific from the beginning) and for whatever reason it does not support the creation of multiple labels and does not even set the self-hosted label on any registered runners; the runner is just stuck with a singular label with whatever the value to runnerScaleSetName is.

Currently we've worked around this by setting the value to just ${{ vars.SOME_VAR }}, which satisfies the regular expression (see below), but I'm trying to find out if there's something I can do in CUE as well to make things a bit nicer, subjectively.

The regular expression:

#stringContainingExpressionSyntax: =~"""
	^.*\\$\\{\\{(.|[\r
	])*\\}\\}.*$
	"""