False positive object, array, and null values should not be evaluated in template with ${{ }} with lists in matrix

[nantiferov]

Hi,

I think I might found a bug related to feature added in v1.6.2, actionlint now checks evaluated values at ${{ }} are not an object nor an array since they are not useful

Example below produces this error, however it's a valid workflow and recommended for self-hosted runners (multiple tags to select runner).
https://docs.github.com/en/actions/learn-github-actions/workflow-syntax-for-github-actions#example-7

Link to playground

Error message:
object, array, and null values should not be evaluated in template with ${{ }} but evaluating the value of type array<string> [expression]

Example:

name: test
on: [push]
jobs:
  test:
    runs-on: ${{ matrix.runner }}
    strategy:
      matrix:
       include:
         - runner: 
           - arm64
           - linux
         - runner:  
            - x64
            - linux
    steps:
      - name: Echo details
        env:
          RUNNER: ${{ matrix.runner }}
        run: echo $RUNNER

I tried to change it to ${{ toJSON(matrix.runner) }}, actionlint passes after that, but workflow is broken after that.

[dekimsey]

I ran into this with another variation of this is that is also supported behavior by GHA:

jobs:
  build:
    strategy:
      matrix:
        include:
          - { runner: [os=macos, x64]}
          - { runner: [os=macos-arm, arm64]}
      fail-fast: false
    runs-on: [self-hosted, "${{matrix.runner}}"]
    steps:
      ...

[rhysd]

actionlint looks correct to me. matrix.runner is an array, not a string. So it cannot be embedded with ${{ }}. You need to put each elements

- run: echo ${{ matrix.runner[0] }} ${{ matrix.runner[1] }}

or serialize it to JSON string

- run: echo ${{ toJSON(matrix.runner) }}