Fix data race on GIDGoogleUser tokens

.github/workflows/unit_tests.yml

@@ -68,6 +68,31 @@ jobs:
           -destination ${{ matrix.destination }} \
           test-without-building
 
+  thread-sanitizer-test:
+    # Run the iOS unit tests with Thread Sanitizer so data races (for example on
+    # GIDGoogleUser's token properties) fail CI instead of shipping silently.
+    runs-on: macos-15
+    steps:
+    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+    - name: Select Xcode
+      run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
+    - name: Build unit test target with Thread Sanitizer
+      run: |
+        xcodebuild \
+          -scheme GoogleSignIn-Package \
+          -sdk iphonesimulator \
+          -destination "platform=iOS Simulator,name=iPhone 16,OS=18.6" \
+          -enableThreadSanitizer YES \
+          build-for-testing
+    - name: Run unit test target with Thread Sanitizer
+      run: |
+        xcodebuild \
+          -scheme GoogleSignIn-Package \
+          -sdk iphonesimulator \
+          -destination "platform=iOS Simulator,name=iPhone 16,OS=18.6" \
+          -enableThreadSanitizer YES \
+          test-without-building
+
   signin-sample-spm-build:
     runs-on: macos-15
     steps:

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 - Fix a crash when a server error response carries a non-string value under its `error` key. The EMM error handler sent `-hasPrefix:` to whatever value was present, raising an unrecognized selector exception on a number, array or object.
 - Fix a custom `nonce` and requested token `claims` being dropped when a sign-in is continued after a Device Policy app restart.
+- Fix a data race on `GIDGoogleUser`'s access, refresh and ID tokens. Concurrent token refreshes could previously write the three properties from different queues at once, and readers could observe a partially-updated set.
 
 # 10.0.0
 - **BREAKING**: Update to AppAuth 3.0.0 and GTMAppAuth 6.0.0, which raises the minimum deployment targets to iOS 15.0 and macOS 12.0, widens the `GTMSessionFetcher` dependency to allow 4.x and 5.x, and renames the version-specific Swift Package Manager manifest to `Package@swift-5.7.swift`. Projects that must keep supporting earlier OS versions should stay on GoogleSignIn 9.2.0. ([#628](https://github.com/google/GoogleSignIn-iOS/pull/628))