Automatically detect runtimes to install based on files in the repository

[strawgate]

Current behavior: runtime (go, python, uv) setup is driven by runtimes: and/or detection; steps run whenever that runtime is selected. Detection is done by parsing the custom steps for commands to create runtimes from.

In my use-case im centrally defining workflows that are workflow_call-ed. In this case a user can't provide the runtime keys they need nor can they provide steps that can be detected at compile time.

It would be nice if runtimes could contain an if conditional that could default (or at least be used) to detecting the presence of certain well known files like install the go runtime if go.mod exists, install the uv runtime if uv.lock exists, etc.

[pelikhan]

do you have some simple code samples?

[strawgate]

Basically I'm getting this behavior now by adding steps that have the following configuration:

---
steps:
  - name: Setup Go
    if: hashFiles('go.mod') != ''
    uses: actions/setup-go@v5
    with:
      go-version-file: go.mod
      cache: true

  - name: Setup Python
    if: hashFiles('.python-version') != ''
    uses: actions/setup-python@v5
    with:
      python-version-file: '.python-version'

  - name: Setup Node.js
    if: hashFiles('.node-version', '.nvmrc') != ''
    uses: actions/setup-node@v6
    with:
      node-version-file: '.node-version'

  - name: Setup Ruby
    if: hashFiles('.ruby-version') != ''
    uses: ruby/setup-ruby@v1
    with:
      ruby-version: '.ruby-version'
      bundler-cache: true

  - name: Setup uv
    if: hashFiles('pyproject.toml', 'uv.lock') != ''
    uses: astral-sh/setup-uv@v5
---

This is a slightly older example but I think shows the idea

So basically we could add if support to the runtime blocks and maybe have an auto mode or something if we wanted it to be automatic

Or I could just keep doing this with steps

[pelikhan]

@copilot update runtimes to specify a custom if condition that gets merged in the generated steps.