Reuse portion of github action across jobs

Since Oct. 2021, "Reusable workflows are generally available"

Reusable workflows are now generally available.
Reusable workflows help you reduce duplication by enabling you to reuse an entire workflow as if it were an action. A number of improvements have been made since the beta was released in October:

• You can utilize outputs to pass data from reusable workflows to other jobs in the caller workflow
• You can pass environment secrets to reusable workflows
• The audit log includes information about which reusable workflows are used

See "Reusing workflows" for more.

A workflow that uses another workflow is referred to as a "caller" workflow.
The reusable workflow is a "called" workflow.

One caller workflow can use multiple called workflows.
Each called workflow is referenced in a single line.

The result is that the caller workflow file may contain just a few lines of YAML, but may perform a large number of tasks when it's run. When you reuse a workflow, the entire called workflow is used, just as if it was part of the caller workflow.

Example:

In the reusable workflow, use the inputs and secrets keywords to define inputs or secrets that will be passed from a caller workflow.

# .github/actions/my-action.yml
# Note the special trigger 'on: workflow_call:'

on:
  workflow_call:
    inputs:
      username:
        required: true
        type: string
    secrets:
      envPAT:
        required: true

Reference the input or secret in the reusable workflow.

jobs:
  reusable_workflow_job:
    runs-on: ubuntu-latest
    environment: production
    steps:
      - uses: ./.github/actions/my-action
        with:
          username: ${{ inputs.username }}
          token: ${{ secrets.envPAT }}

With ./.github/actions/my-action the name of the my-action.yml file in your own repository.

A reusable workflow does not have to be in the same repository, and can be in another public one.

Davide Benvegnù aka CoderDave illustrates that in "Avoid Duplication! GitHub Actions Reusable Workflows" where:

• n3wt0n/ActionsTest/.github/workflows/reusableWorkflowsUser.yml references
• n3wt0n/ReusableWorkflow/.github/workflows/buildAndPublishDockerImage.yml@main

As I know currently there is no way to reuse steps
but in this case, you can use strategy for parallel build and different variation:

jobs:
  build:
    name: Build
    runs-on: macos-latest
    strategy:
      matrix:
        build-dir: ['apps/wear/pushtracker', 'apps/wear/smartdrive']
    steps:
      - name: Checkout Repo
        uses: actions/checkout@v1

      - name: Setup SSH-Agent
        uses: webfactory/[email protected]
        with:
          ssh-private-key: |
            ${{ secrets.SSH_PRIVATE_KEY }}

      - name: Setup JDK 1.8
        uses: actions/setup-java@v1
        with:
          java-version: 1.8

      - name: Setup Permobil-Client
        run: |
          echo no | npm i -g nativescript
          tns usage-reporting disable
          tns error-reporting disable
          npm run setup.all

      - name: Build Android
        run: |
          cd ${{ matrix.build-dir }}
          tns build android --env.uglify

For more information please visit https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions#jobsjob_idstrategy

There are 3 main approaches for code reusing in GitHub Actions:

• Reusable Workflows
• Dispatched workflows
• Composite Actions <-- it's the best one in your case

The following details are from my article describing their pros and cons:

🔸 Reusing workflows

The obvious option is using the "Reusable workflows" feature that allows you to extract some steps into a separate "reusable" workflow and call this workflow as a job in other workflows.

🥡 Takeaways:

• Reusable workflows can't call other reusable workflows.
• The strategy property is not supported in any job that calls a reusable workflow.
• Env variables and secrets are not inherited.
• It's not convenient if you need to extract and reuse several steps inside one job.
• Since it runs as a separate job, you have to use build artifacts to share files between a reusable workflow and your main workflow.
• You can call a reusable workflow in synchronous or asynchronous manner (managing it by jobs ordering using needs keys).
• A reusable workflow can define outputs that extract outputs/outcomes from executed steps. They can be easily used to pass data to the "main" workflow.

🔸 Dispatched workflows

Another possibility that GitHub gives us is workflow_dispatch event that can trigger a workflow run. Simply put, you can trigger a workflow manually or through GitHub API and provide its inputs.

There are actions available on the Marketplace which allow you to trigger a "dispatched" workflow as a step of "main" workflow.

Some of them also allow doing it in a synchronous manner (wait until dispatched workflow is finished). It is worth to say that this feature is implemented by polling statuses of repo workflows which is not very reliable, especially in a concurrent environment. Also, it is bounded by GitHub API usage limits and therefore has a delay in finding out a status of dispatched workflow.

🥡 Takeaways

• You can have multiple nested calls, triggering a workflow from another triggered workflow. If done careless, can lead to an infinite loop.
• You need a special token with "workflows" permission; your usual secrets.GITHUB_TOKEN doesn't allow you to dispatch a workflow.
• You can trigger multiple dispatched workflows inside one job.
• There is no easy way to get some data back from dispatched workflows to the main one.
• Works better in "fire and forget" scenario. Waiting for a finish of dispatched workflow has some limitations.
• You can observe dispatched workflows runs and cancel them manually.

🔸 Composite Actions

In this approach we extract steps to a distinct composite action, that can be located in the same or separate repository.

From your "main" workflow it looks like a usual action (a single step), but internally it consists of multiple steps each of which can call own actions.

🥡 Takeaways:

• Supports nesting: each step of a composite action can use another composite action.
• Bad visualisation of internal steps run: in the "main" workflow it's displayed as a usual step run. In raw logs you can find details of internal steps execution, but it doesn't look very friendly.
• Shares environment variables with a parent job, but doesn't share secrets, which should be passed explicitly via inputs.
• Supports inputs and outputs. Outputs are prepared from outputs/outcomes of internal steps and can be easily used to pass data from composite action to the "main" workflow.
• A composite action runs inside the job of the "main" workflow. Since they share a common file system, there is no need to use build artifacts to transfer files from the composite action to the "main" workflow.
• You can't use continue-on-error option inside a composite action.