Expression for array concatenation

[alexbatashev]

Currently documentation features expressions for checking if array contains a value or joining an array into a string, but there's no way to merge two arrays or append a value to an array.

A possible use case is adding more runner labels for reusable workflows, i.e.:

on:
  workflow_call:
    inputs:
      os:
         type: string
         default: "Linux"

some_job:
  runs-on: ${{ concat([x64, build], inputs.os) }}

This is currently possible with some sort of configuration job dependency, but would be nice if one could do it instantly.

[ethomson]

Thanks @alexbatashev - I appreciate the feedback. This is on our backlog but I don't know when we'll work on it.

[jsoref]

You can work around this using fromJSON w/ an extra job that does the array merging using jq or whatever program you like.

(Obviously it'd be nicer to have native primitives and not require an extra job.)

[sdarwin]

Hi @jsoref I just googled: github actions concatenate array, and this was the top post, which turns out to exactly matched the use case I had in mind. "adding more runner labels". I would like to add labels to runs-on: ${{ concat([x64, build], inputs.os) }} . Could you provide the fromJSON example that you mention?

[alexbatashev]

I was doing some CI stuff at one of my previous jobs. We needed to prepare a complex test matrix, that would include different hardware and software depending on the platform. Here's an example: https://github.com/intel/llvm/blob/6a3b4da3452fc02b6ae4c11dd36aab9aeb86893d/.github/workflows/sycl_linux_build_and_test.yml#L193

And the JSON input is generated one level above: https://github.com/intel/llvm/blob/sycl/.github/workflows/sycl_precommit.yml

Seems to be working for over a year now.

[sdarwin]

thanks I will check it out

[ChristopherHX]

Doing this in pure actions yaml, without a job doing the work is pretty easy if you know the syntax

runs-on:
- x64
- build
- ${{ inputs.os }} # assumes `inputs.os` is a string

runs-on: [x64, build, "${{ inputs.os }}"] # assumes `inputs.os` is a string, quotes are required due to json like notation and `{`/`}` brackets.

Now some examples using json in inputs.os

runs-on:
- x64
- build
- ${{ fromjson(inputs.os) }} # assumes `inputs.os` is a json string literal or a json array (if it is an array the list of labels is appended by the json lst)

runs-on: [x64, build, "${{ fromjson(inputs.os) }}"] # assumes `inputs.os` is a json string literal or a json array (if it is an array the list of labels is appended by the json lst), quotes are required due to json like notation and `{`/`}` brackets.