GitHub CI Path Filtering

This repository keeps the pull_request trigger unconditional and performs path filtering inside the workflow using dorny/paths-filter, so that every pull request always reports a status for each required check. The rationale for this pattern is described in GitHub Branch Protection Rationale; the settings that consume it are in Configure GitHub Repository Protection.

Workflow structure

Both CI workflows in this repository use this pattern. The example below is java-build-test.yml; frontend-build-test.yml is identical in structure (substituting frontend/** and react-build-and-test).

# .github/workflows/java-build-test.yml  (frontend-build-test.yml is identical in structure)
on:
  push:
    branches: [ main ]
    paths:
      - 'backend/**'
      - '.github/workflows/java-build-test.yml'
  pull_request:
    branches: [ main ]          # no paths filter here

jobs:
  filter:
    runs-on: ubuntu-latest
    outputs:
      backend: $
    steps:
      - uses: actions/checkout@v4
      - uses: dorny/paths-filter@v3
        id: changes
        with:
          filters: |
            backend:
              - 'backend/**'

  java-build-and-test:
    needs: filter
    if: needs.filter.outputs.backend == 'true'
    # ... full build steps ...

  skip-check:
    needs: filter
    if: needs.filter.outputs.backend != 'true'
    runs-on: ubuntu-latest
    steps:
      - run: echo "No backend changes, skipping the build"

• If the relevant directory was changed → the build and test job runs.
• Otherwise → the lightweight skip-check job runs, prints an explanatory message, and exits successfully.

The push trigger retains its paths filter for post-merge runs (for example, to trigger a deployment after a PR is merged).

Status-reporting matrix

Scenario	filter job	Build job	Status reported
PR touches backend/**	runs, output true	java-build-and-test runs	✅ pass / ❌ fail
PR does not touch backend/**	runs, output false	skipped	skip-check → ✅ pass
PR touches frontend/**	runs, output true	react-build-and-test runs	✅ pass / ❌ fail
PR does not touch frontend/**	runs, output false	skipped	skip-check → ✅ pass

Required-check configuration

Job	Add as required check?
java-build-and-test	✅ Yes
react-build-and-test	✅ Yes
skip-check	❌ No — a skipped required job is counted as passing by GitHub; requiring skip-check would block PRs that change only one stack

The job name used in the branch protection rule must match the job id in the workflow YAML exactly (case-sensitive). GitHub does not offer auto-complete for jobs that have never run — trigger the workflow at least once (for example, by opening a draft pull request) before configuring the rule.