GitHub Action: Run hlint

See also haskell-actions/hlint-setup, which will install (and cache) HLint.

Executes hlint and presents the output using actions/toolkit/commands/problem matcher, so hints are displayed as GitHub annotations.

• fail-on (optional, default: never): When to mark the check as failed. One of: never, status, warning, suggestion, or error.
• path (required): The single file or directory name, or formatted JSON array containing multiple. Examples:
  • - path: src/
  • - path: '["src/", "test/"]'
  • - path: ${{ toJSON(steps.whatever.changed_dirs) }} (see: docs on toJSON)
• hlint-bin (optional): The hlint binary path, if not already in PATH.

The main purpose of this action currently is just to print out GitHub annotations, but it still provides an output.

• ideas: The generated HLint ideas (warnings, errors, etc.) serialized to JSON.

name: lint
on:
  pull_request:
  push:
    branches:
      - master
      - 'releases/*'

jobs:
  hlint:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v4

    - name: 'Set up HLint'
      uses: haskell-actions/hlint-setup@v2
      with:
        version: '3.1.6'

    - name: 'Run HLint'
      uses: haskell-actions/hlint-run@v2
      with:
        path: src/
        fail-on: warning