ci: Add unit tests required check (#5885)

Use dorny path filters to have one single job failing or succeeding when
the unit tests passed or were skipped so we can enable unit tests
as required checks for PRs.

Fixes GH-5868

Author: philipphofmann

.github/file-filters.yml

@@ -15,3 +15,27 @@ high_risk_code: &high_risk_code
   - "Sources/Sentry/SentryFileManager.m"
   - "Sources/Sentry/SentrySerialization.m"
   - "Sources/Sentry/SentrySerialization.h"
+
+run_unit_tests_for_prs: &run_unit_tests_for_prs # Code
+  - "Sources/**"
+  - "Tests/**"
+  - "SentryTestUtils/**"
+  - "SentryTestUtilsDynamic/**"
+
+  # GH Actions
+  - ".github/workflows/test.yml"
+  - ".github/file-filters.yml"
+
+  # Scripts
+  - "scripts/ci-select-xcode.sh"
+  - "scripts/sentry-xcodebuild.sh"
+  - "scripts/tests-with-thread-sanitizer.sh"
+
+  # Other
+  - "test-server/**"
+  - "Sentry.xcodeproj"
+  - "**/*.xctestplan"
+  - "fastlane/**"
+  - ".codecov.yml"
+  - "Brewfile*" # Dependency installation affects test environment
+  - "Makefile" # Make commands used for CI build setup

.github/workflows/test.yml

@@ -6,22 +6,6 @@ on:
       - release/**
 
   pull_request:
-    paths:
-      - "Sources/**"
-      - "Tests/**"
-      - "SentryTestUtils/**"
-      - "SentryTestUtilsDynamic/**" # Dynamic test utilities used by tests
-      - "test-server/**"
-      - ".github/workflows/test.yml"
-      - "fastlane/**"
-      - "scripts/tests-with-thread-sanitizer.sh"
-      - "scripts/ci-select-xcode.sh"
-      - "scripts/sentry-xcodebuild.sh"
-      - ".codecov.yml"
-      - "Sentry.xcodeproj"
-      - "**/*.xctestplan"
-      - "Makefile" # Make commands used for CI build setup
-      - "Brewfile*" # Dependency installation affects test environment
 
 # Concurrency configuration:
 # - We use workflow-specific concurrency groups to allow independent test runs across different workflows
@@ -35,8 +19,29 @@ concurrency:
   cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 jobs:
+  # This job detects if the PR contains changes that require running unit tests.
+  # If yes, the job will output a flag that will be used by the next job to run the unit tests.
+  # If no, the job will output a flag that will be used by the next job to skip running the unit tests.
+  # At the end of this workflow, we run a check that validates that either all unit tests passed or were
+  # called unit-tests-required-check.
+  files-changed:
+    name: Detect File Changes
+    runs-on: ubuntu-latest
+    # Map a step output to a job output
+    outputs:
+      run_unit_tests_for_prs: ${{ steps.changes.outputs.run_unit_tests_for_prs }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Get changed files
+        id: changes
+        uses: dorny/paths-filter@de90cc6fb38fc0963ad72b210f1f284cd68cea36 # v3.0.2
+        with:
+          token: ${{ github.token }}
+          filters: .github/file-filters.yml
   build-test-server:
     name: Build test server
+    if: needs.files-changed.outputs.run_unit_tests_for_prs == 'true'
+    needs: files-changed
     runs-on: macos-15
     steps:
       - uses: actions/checkout@v4
@@ -306,3 +311,25 @@ jobs:
           verbose: true
           name: sentry-cocoa-unit-tests
           flags: unittests-${{ matrix.platform }}-${{ matrix.xcode }}-${{ matrix.test-destination-os }}, unittests
+
+  # This check validates that either all unit tests passed or were skipped, which allows us
+  # to make unit tests a required check with only running the unit tests when required.
+  # So, we don't have to run unit tests, for example, for Changelog or ReadMe changes.
+
+  unit-tests-required-check:
+    needs:
+      [
+        build-test-server,
+        unit-tests,
+      ]
+    name: Unit Tests
+    # This is necessary since a failed/skipped dependent job would cause this job to be skipped
+    if: always()
+    runs-on: ubuntu-latest
+    steps:
+      # If any jobs we depend on fails gets cancelled or times out, this job will fail.
+      # Skipped jobs are not considered failures.
+      - name: Check for failures
+        if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')
+        run: |
+          echo "One of the unit test jobs has failed." && exit 1