action.yml

name: 'ESLint for Pull Requests'
description: 'Action that eslints your code and reports only the problems introduced by your pull request'
inputs:
  npm-token:
    description: 'Token for accessing private NPM packages, ie custom linter settings. Usually {{ secrets.NPM_TOKEN }}, if required.'
    required: false
    default:
  eslint-config-package:
    description: 'Package to install for custom ESLint config, if required. Something like @org/eslint-config-custom-rules.'
    required: false
    default:
  eslint-config-base:
    description: 'Name of ESLint config to use, if not provided in repo (ie through .eslintrc). Something like @org/custom-rules.'
    required: false
    default:
outputs:
  random-number: 
    description: "Random number"
    value: ${{ steps.random-number-generator.outputs.random-id }}
runs:
  using: "composite"
  steps:
  - name: Setup Node.js
    uses: actions/setup-node@v1
    with:
      node-version: 10.x
  - name: Checkout branch
    uses: actions/checkout@v2
  - name: Cache node modules
    id: cache_npm
    uses: pat-s/always-upload-cache@v2.1.0
    env:
      cache-name: node-modules
    with:
      path: node_modules
      key: ${{ runner.os }}-lint-${{ env.cache-name }}-3
  - name: Install eslint
    if: steps.cache_npm.outputs.cache-hit == false
    env:
      NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
    run: |
      rm package.json
      echo "//registry.npmjs.org/:_authToken=${NPM_TOKEN}" > ~/.npmrc
      npm install eslint --no-save
  - name: Install linter config
    if: inputs.eslint-config-package
    if: steps.cache_npm.outputs.cache-hit == false
    env:
      NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
    run: |
      npm install ${{ inputs.eslint-config-package }}
  - name: Create linter config file
    if: inputs.eslint-config-base
    run: |
      echo '{"extends":"'${{ inputs.eslint-config-base }}'"}' > _ci-eslint-config.json
  - name: Run linter for current
    run: |
      npx eslint -c _ci-eslint-config.json -f compact . > result-current || true
  - name: Cache linter baseline
    id: cache_baseline
    uses: pat-s/always-upload-cache@v2.1.0
    env:
      cache-name: lint-results-base
    with:
      path: result-base
      key: ${{ runner.os }}-lint-${{ env.cache-name }}-${{ github.event.pull_request.base.sha }}
  - name: Checkout base (${{ github.base_ref }})
    if: steps.cache_baseline.outputs.cache-hit == false
    uses: actions/checkout@v2
    with:
      ref: ${{ github.base_ref }}
      path: _ci-checkout-base
  - name: Run linter for baseline
    if: steps.cache_baseline.outputs.cache-hit == false
    run: |
      npx eslint -c _ci-eslint-config.json -f compact _ci-checkout-base | sed -e's/\/_ci-checkout-base//' > result-base || true
  - name: Find differences and report
    run: |
      # Mask the line numbers and see if there is any difference then. If not, differences are caused by changed line numbers.
      # We mask them with regexes, so we can use them to filter all changed lines later
      # diff to find the difference. Use sed on both inputs to replace the line number by a regex that matches anything until the next comma.
      # grep to filter only the lines that start with a single '+' (additions)
      # sed to remove the '+'s at the start of the lines
      # grep -v to remove the (possible) line sayin n problem(s)
      # true to make sure to not return non-zero exit code (when diff is empty)
      diff -u0 <(cat result-base | sed -e 's/: line\([^,]*\)/: line \\([^,]*\\)/' ) <(cat result-current | sed -e 's/: line\([^,]*\)/: line \\([^,]*\\)/') | grep "^+[^+]" | sed -E 's/^\+//' | grep -v "problem$\|problems$" > result-diff-masked || true
      # Combine the masked lines into one line, each original line separated by '\|' (grep OR) so we can use it to filter the matching problems from all current problems - which include the correct line numbers
      FILTER=$(cat result-diff-masked | sort -u | awk 'ORS="\\|"' | sed 's/\\|$//')
      # If filter is empty grep would match everything; make it a regex that doesn't match anything instead
      if [ -z "$FILTER" ] ; then FILTER="^$" ; fi
      # As above, but leaving the line numbers in this time
      diff -u0 result-base result-current | grep "^+[^+]" | sed -E 's/^\+//' | grep -v "problem$\|problems$" | grep "$FILTER" || true
      # Return non-zero code if the masked diff yielded any lines
      [ -z "$(cat result-diff-masked)" ]
        
        
#    steps: 
#    - run: echo Hello ${{ inputs.who-to-greet }}.
#      shell: bash
#    - id: random-number-generator
#      run: echo "::set-output name=random-id::$(echo $RANDOM)"
#      shell: bash
#    - run: ${{ github.action_path }}/goodbye.sh
#      shell: bash