How to filter required checks that run during a PR, which is useful for mono-repos.

filtered-pr-checks.yml

name: "Pre-Merge Checks"

on:
  workflow_dispatch:
  pull_request:
    branches: [ dev ]
# We only trigger long running tests on demand from another workflow
  workflow_call:
    inputs:
      label_trigger:
        required: true
        type: boolean

jobs:
  changes:
    name: 'Check for changes'
    runs-on: ubuntu-latest
    permissions:
      pull-requests: read
    outputs:
      backend: ${{ steps.filter.outputs.backend }}
      frontend: ${{ steps.filter.outputs.frontend }}
    steps:
    - uses: dorny/paths-filter@v2
      id: filter
      with:
        filters: |
          backend:
            - 'Backend/**'
          frontend:
            - 'Frontend/**'
  
  verify-formatting:
    name: 'Verify Formatting'
    runs-on: ubuntu-latest
    needs: changes
    if: ${{ needs.changes.outputs.backend == 'true' && !inputs.label_trigger }}
    steps:
      - uses: actions/checkout@v3
      - name: Setup .NET
        uses: actions/setup-dotnet@v3
        with:
          dotnet-version: 6.0.x
 # Verify the formatting of our dotnet backend here

  restore-build-test:
    name: 'Restore Build Test'
    runs-on: windows-latest
    if: ${{ inputs.label_trigger && needs.changes.outputs.backend == 'true' }}
    needs: changes
    steps:
    - uses: actions/checkout@v3
# We run our long running tests here, but only if called from the other workflow

  lint-build-frontend:
    name: 'Lint Build Frontend'
    runs-on: ubuntu-latest
    needs: changes
    if: ${{ needs.changes.outputs.frontend == 'true' && !inputs.label_trigger }}
    steps:
    - uses: actions/checkout@v3
# Lint and build our frontend