Firestore: Fix data race in credentials provider (#10403)

Author: dconeybe

Firestore/CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 - [fixed] Fix FAILED_PRECONDITION when writing to a deleted document in a
   transaction (#10431).
+- [fixed] Fixed data race in credentials provider (#10393).
 
 # 10.0.0
 - [feature] Added `Query.count()`, which fetches the number of documents in the

Firestore/core/src/credentials/credentials_provider.h

@@ -17,6 +17,7 @@
 #ifndef FIRESTORE_CORE_SRC_CREDENTIALS_CREDENTIALS_PROVIDER_H_
 #define FIRESTORE_CORE_SRC_CREDENTIALS_CREDENTIALS_PROVIDER_H_
 
+#include <atomic>
 #include <functional>
 #include <string>
 
@@ -46,6 +47,7 @@ template <class TokenType, class ValueType>
 class CredentialsProvider {
  public:
   CredentialsProvider() : change_listener_(nullptr) {
+    force_refresh_ = false;
   }
 
   virtual ~CredentialsProvider() = default;
@@ -81,7 +83,7 @@ class CredentialsProvider {
    */
   CredentialChangeListener<ValueType> change_listener_;
 
-  bool force_refresh_ = false;
+  std::atomic<bool> force_refresh_;
 };
 
 }  // namespace credentials

Firestore/core/test/unit/credentials/firebase_auth_credentials_provider_test.mm

@@ -153,6 +153,28 @@ - (void)getTokenForcingRefresh:(BOOL)forceRefresh
   });
 }
 
+// Catch race conditions in FirebaseAuthCredentialsProvider::GetToken() when
+// run under thread sanitizer.
+// See https://github.com/firebase/firebase-ios-sdk/issues/10393
+TEST(FirebaseAuthCredentialsProviderTest, GetTokenCalledByAnotherThread) {
+  FIRApp* app = testutil::AppForUnitTesting();
+  FSTAuthFake* auth = [[FSTAuthFake alloc] initWithToken:@"token for fake uid"
+                                                     uid:@"fake uid"];
+  FirebaseAuthCredentialsProvider credentials_provider(app, auth);
+
+  std::thread thread1([&credentials_provider] {
+    credentials_provider.GetToken(
+        [](util::StatusOr<AuthToken> result) { EXPECT_TRUE(result.ok()); });
+  });
+  std::thread thread2([&credentials_provider] {
+    credentials_provider.GetToken(
+        [](util::StatusOr<AuthToken> result) { EXPECT_TRUE(result.ok()); });
+  });
+
+  thread1.join();
+  thread2.join();
+}
+
 }  // namespace credentials
 }  // namespace firestore
 }  // namespace firebase