API for explicitly declared environment variables in workflow

[jacob-carlborg]

🏷️ Discussion Type

Product Feedback

💬 Feature/Topic Area

Other

Discussion Details

I would like an API, of some kind, to get access to those environment variables explicitly declared in a workflow file using the env: syntax.

I'm the author of the Cross-Platform Action [1], which is a GitHub action that starts a virtual machine (VM). To expose environment variables inside the VM that are declared outside, the user currently needs to explicitly list which environment variables should be exposed inside the VM. It would be a better user experience if the action could automatically expose all environment variables the user is interested in. It wouldn't make sense to expose all environment variables that are available outside the VM, because that would cause conflict with environment variables inside the VM like PWD and HOME. Instead if there could be an API that allows the action to only get the environment variables (the names and the values) that are explicitly declared using the env: syntax, MY_ENV1 and MY_ENV2 in the example below. It shouldn't matter at which level the in the workflow file the environment variables are declared.

name: CI

on: [push]

jobs:
  test:
    runs-on: ubuntu-latest
    defaults:
      run:
        shell: cpa.sh {0}

    steps:
      - uses: actions/checkout@v6

      - name: Start VM on ${{ matrix.os.name }}
        uses: cross-platform-actions/action@v1.2.0
        env:
          MY_ENV1: foo
          MY_ENV2: bar
        with:
          environment_variables: MY_ENV1 MY_ENV2 # need to explicitly specify which environment variables should be exposed
          operating_system: freebsd
          version: 15.0

      - name: Print env
        run: |
          echo $MY_ENV1
          echo $MY_ENV2

[1] https://github.com/cross-platform-actions/action

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[tanvishinde017]

This seems like a reasonable feature request.

Currently, actions can access the runtime environment, but there isn't a supported way (that I'm aware of) to distinguish:

• variables explicitly declared by the workflow author via env:
• variables injected by GitHub (GITHUB_*, RUNNER_*, etc.)
• variables introduced by the runner or operating system

For actions like Cross-Platform Action, automatically forwarding only user-defined env: variables would provide a much better experience and avoid collisions with VM-specific variables such as HOME, PWD, or platform defaults.

One possible implementation could be:

• a new context exposing only workflow-defined environment variables;
• metadata attached to environment variables indicating their origin;
• or an API that returns the merged env: values after inheritance (workflow → job → step).

That would remove the need for:

with:
  environment_variables: MY_ENV1 MY_ENV2

and allow actions to safely propagate only the variables intentionally provided by the user.

Until something like this exists, explicitly listing the variables is probably the safest approach from both a compatibility and security standpoint.

👍 I can definitely see this being useful for VM/container actions and other environment-isolation tools.