Github Actions dynamic container name

Question

Summary:

Github Actions allows using Docker containers to run jobs, but it doesn't seem to allow providing a dynamic value for this container image (using environment variables).

This works (not the desired solution):

jobs:
  pytest-test:
    container:
      image: ghcr.io/ashrafgt/test:latest    ...

This does not work (the desired solution):

jobs:
  pytest-test:
    container:
      # env variables defined at the start of the workflow
      image: ${{ env.REGISTRY_NAME }}/test:${{ env.IMAGE_TAG }} 
    ...

Giving this error:

Invalid workflow file : .github/workflows/workflow.yaml
The workflow is not valid. Unrecognized named-value: 'env'. Located at position 1 within expression: env.REGISTRY_NAME

Are there any ways to do this besides doing a run: docker run ...?

Full Example:

In this example, I try to build and push a Docker image (tagged with the current commit SHA) then use the same image to run unit tests:

name: Main CI Pipeline

on: [push]

env:
  REGISTRY_NAME: ghcr.io/${{ github.repository_owner }}
  REGISTRY_USERNAME: ${{ github.actor }}
  REGISTRY_PASSWORD: ${{ secrets.GITHUB_TOKEN }}
  IMAGE_TAG: ${{ github.sha }}

jobs:

  docker-build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
    steps:
      - uses: actions/checkout@v2
      - uses: docker/setup-buildx-action@v1
      - uses: docker/login-action@v1
        with:
          registry: ${{ env.REGISTRY_NAME }}
          username: ${{ env.REGISTRY_USERNAME }}
          password: ${{ env.REGISTRY_PASSWORD }}
      - uses: docker/build-push-action@v2
        with:
          tags: ${{ env.REGISTRY_NAME }}/test:${{ env.IMAGE_TAG }}
          push: true

  pytest-test:
    needs: docker-build
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: read
    container:
      image: ${{ env.REGISTRY_NAME }}/test:${{ env.IMAGE_TAG }}
    steps:
      - uses: actions/checkout@v2
      - run: pytest

Please find the full repository here.

The full error message is:

Invalid workflow file : .github/workflows/workflow.yaml#L38
The workflow is not valid. .github/workflows/workflow.yaml (Line: 38, Col: 14): Unrecognized named-value: 'env'. Located at position 1 within expression: env.REGISTRY_NAME

Please find the Github Actions run here.

Fix Attempts:

1. Using only container instead of container.image:

   jobs:
     pytest-test:
       container: ${{ env.REGISTRY_NAME }}/test:${{ env.IMAGE_TAG }} 
       ...
   

2. Using the docker:// syntax for a single step:

   jobs:
     pytest-test:
       steps:
         - uses: docker://${{ env.REGISTRY_NAME }}/test:${{ env.IMAGE_TAG }}
           entrypoint: pytest
       ...
   

Both fix attempts failed with the same error as the original syntax.

Answer 1

env context is not available for container or container.image. Following is a snapshot from the GitHub Actions plugin on VSCode where the linter throws an error.

Alternatively, you can define configuration variables in GitHub at a repo/org level and then use the vars context to access it (example)