Ensure PR workflows can run on all PRs (but still skip when they're not needed)

.github/workflows/ansible-lint.yaml

@@ -1,14 +1,42 @@
 name: ansible-lint
-on:
-  push:
-    paths:
-      - 'ansible/**'
-  pull_request:
-    paths:
-      - 'ansible/**'
+
+on: [push, pull_request]
+
+# Cancel in progress workflows on pull_requests.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-using-a-fallback-value
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
 
 jobs:
+  # In order to be able to have required checks, a workflow can't be entirely
+  # skipped: see https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks
+  paths-filter:
+    name: "Filter Paths"
+    runs-on: ubuntu-latest
+    outputs:
+      matches: ${{ steps.filter.outputs.matches }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 2  # important, to fetch previous commit
+
+      # workaround for https://github.com/dorny/paths-filter/issues/240
+      - id: previous-sha
+        run: 'echo "sha=$(git rev-parse HEAD^1)" >> $GITHUB_OUTPUT'
+
+      - uses: dorny/paths-filter@v3
+        id: filter
+        with:
+          base: "${{ steps.previous-sha.outputs.sha }}"
+          filters: |
+            matches:
+              - 'ansible/**'
+              - '.github/workflows/ansible-lint.yaml'
+
   build:
+    needs: paths-filter
+    if: needs.paths-filter.outputs.matches == 'true'
     name: Ansible Lint
     runs-on: ubuntu-latest
 

.github/workflows/backend-lint.yaml

@@ -0,0 +1,69 @@
+name: Backend Lint + Type Check
+
+on: [push, pull_request]
+
+# Cancel in progress workflows on pull_requests.
+# https://docs.github.com/en/actions/using-jobs/using-concurrency#example-using-a-fallback-value
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  # In order to be able to have required checks, a workflow can't be entirely
+  # skipped: see https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks
+  paths-filter:
+    name: "Filter Paths"
+    runs-on: ubuntu-latest
+    outputs:
+      matches: ${{ steps.filter.outputs.matches }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 2  # important, to fetch previous commit
+
+      # workaround for https://github.com/dorny/paths-filter/issues/240
+      - id: previous-sha
+        run: 'echo "sha=$(git rev-parse HEAD^1)" >> $GITHUB_OUTPUT'
+
+      - uses: dorny/paths-filter@v3
+        id: filter
+        with:
+          base: "${{ steps.previous-sha.outputs.sha }}"
+          filters: |
+            matches:
+              - 'backend/**'
+              - '.github/workflows/backend-lint.yaml'
+
+  unit-tests:
+    needs: paths-filter
+    if: needs.paths-filter.outputs.matches == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout
+        uses: actions/checkout@v2
+
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+
+      - name: Install dependencies
+        run: |
+          cd backend/
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt
+          pip install -r dev-requirements.txt
+
+      - name: Style Check
+        run: |
+          black --check backend/btrixcloud/
+
+      - name: Lint Check
+        run: |
+          cd backend/
+          pylint btrixcloud/
+
+      - name: Type Check
+        run: |
+          cd backend/
+          mypy --install-types --non-interactive --check-untyped-defs btrixcloud/