build-test-recipe.yml

name: build-test-recipe
on:
  workflow_dispatch:
  pull_request:
    branches:
      - 'master'
      - 'master-next'
    paths:
      - '**.bb'
      - '**.inc'

jobs:
  generate-matrix:
    name: Generate matrix for build
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.set-matrix.outputs.matrix }}    
    steps:
    - uses: actions/checkout@v2
    - name: Check changed files
      id: diff
      run: |
        # See https://github.community/t/check-pushed-file-changes-with-git-diff-tree-in-github-actions/17220/10
        if [ $GITHUB_BASE_REF ]; then
          # Pull Request
          git fetch origin $GITHUB_BASE_REF --depth=1
          export DIFF=$( git diff --name-only origin/$GITHUB_BASE_REF $GITHUB_SHA )
          echo "Diff between origin/$GITHUB_BASE_REF and $GITHUB_SHA"
        else
          # Push
          git fetch origin ${{ github.event.before }} --depth=1
          export DIFF=$( git diff --name-only ${{ github.event.before }} $GITHUB_SHA )
          echo "Diff between ${{ github.event.before }} and $GITHUB_SHA"
        fi
        echo "$DIFF"
        # Escape newlines (replace \n with %0A)
        echo "::set-output name=diff::$( echo "$DIFF" | sed ':a;N;$!ba;s/\n/%0A/g' )"
    - name: Set matrix for build
      id: set-matrix
      run: |
        # See https://stackoverflow.com/a/62953566/11948346
        DIFF="${{ steps.diff.outputs.diff }}"
        JSON="{"include":["
          # Loop by lines
          while read path; 
          do
            # Set $directory to substring before /
            directory="$( echo $path | cut -d'/' -f1 -s )"

            if [ -z "$directory" ]; then
              continue # Exclude root directory
            elif [ "$directory" == docs ]; then
              continue # Exclude docs directory
            elif [ "$path" == *.rst ]; then
              continue # Exclude *.rst files
            fi

            # Set $os. "ubuntu-latest" by default. if directory starts with windows, then "windows-latest"
            os="ubuntu-latest"
            if [ "$directory" == windows* ]; then
              os="windows-latest"
            fi

            # Add build to the matrix only if it is not already included
            JSONline="{\"directory\": \"$directory\", \"os\": \"$os\"},"
            if [[ "$JSON" != *"$JSONline"* ]]; then
              JSON="$JSON$JSONline"
            fi
          done 
          echo "$DIFF"

          # Remove last "," and add closing brackets
          if [[ $JSON == *, ]]; then
            JSON="${JSON%?}"
          fi
          JSON="$JSON]}"
          echo $JSON

          # Set output
          echo "::set-output name=matrix::$( echo "$JSON" )"