Expose clearPersistence() publicly (#3026)

Author: Brian Chen

Firestore/CHANGELOG.md

@@ -1,4 +1,7 @@
 # Unreleased
+- [feature] Added `clearPersistence()`, which clears the persistent storage
+  including pending writes and cached documents. This is intended to help
+  write reliable tests (https://github.com/firebase/firebase-js-sdk/issues/449).
 
 # 1.3.2
 - [fixed] Firestore should now recover its connection to the server more

Firestore/Source/API/FIRFirestore+Internal.h

@@ -64,22 +64,6 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)shutdownWithCompletion:(nullable void (^)(NSError *_Nullable error))completion
     NS_SWIFT_NAME(shutdown(completion:));
 
-/**
- * Clears the persistent storage. This includes pending writes and cached documents.
- *
- * Must be called while the firestore instance is not started (after the app is shutdown or when
- * the app is first initialized). On startup, this method must be called before other methods
- * (other than `FIRFirestore.settings`). If the firestore instance is still running, the function
- * will complete with an error code of `FailedPrecondition`.
- *
- * Note: `clearPersistence(completion:)` is primarily intended to help write reliable tests that
- * use Firestore. It uses the most efficient mechanism possible for dropping existing data but
- * does not attempt to securely overwrite or otherwise make cached data unrecoverable. For
- * applications that are sensitive to the disclosure of cache data in between user sessions we
- * strongly recommend not to enable persistence in the first place.
- */
-- (void)clearPersistenceWithCompletion:(nullable void (^)(NSError *_Nullable error))completion;
-
 - (const std::shared_ptr<util::AsyncQueue> &)workerQueue;
 
 @property(nonatomic, assign, readonly) std::shared_ptr<api::Firestore> wrapped;

Firestore/Source/API/FIRFirestore.mm

@@ -267,6 +267,10 @@ - (void)disableNetworkWithCompletion:(nullable void (^)(NSError *_Nullable))comp
   _firestore->DisableNetwork(util::MakeCallback(completion));
 }
 
+- (void)clearPersistenceWithCompletion:(nullable void (^)(NSError *_Nullable error))completion {
+  _firestore->ClearPersistence(util::MakeCallback(completion));
+}
+
 @end
 
 @implementation FIRFirestore (Internal)
@@ -287,10 +291,6 @@ + (BOOL)isLoggingEnabled {
   return util::LogIsLoggable(util::kLogLevelDebug);
 }
 
-- (void)clearPersistenceWithCompletion:(nullable void (^)(NSError *_Nullable error))completion {
-  _firestore->ClearPersistence(util::MakeCallback(completion));
-}
-
 + (FIRFirestore *)recoverFromFirestore:(std::shared_ptr<Firestore>)firestore {
   return (__bridge FIRFirestore *)firestore->extension();
 }

Firestore/Source/Public/FIRFirestore.h

@@ -176,6 +176,22 @@ NS_SWIFT_NAME(Firestore)
  */
 - (void)disableNetworkWithCompletion:(nullable void (^)(NSError *_Nullable error))completion;
 
+/**
+ * Clears the persistent storage. This includes pending writes and cached documents.
+ *
+ * Must be called while the firestore instance is not started (after the app is shutdown or when
+ * the app is first initialized). On startup, this method must be called before other methods
+ * (other than `FIRFirestore.settings`). If the firestore instance is still running, the function
+ * will complete with an error code of `FailedPrecondition`.
+ *
+ * Note: `clearPersistence(completion:)` is primarily intended to help write reliable tests that
+ * use Firestore. It uses the most efficient mechanism possible for dropping existing data but
+ * does not attempt to securely overwrite or otherwise make cached data unrecoverable. For
+ * applications that are sensitive to the disclosure of cache data in between user sessions we
+ * strongly recommend not to enable persistence in the first place.
+ */
+- (void)clearPersistenceWithCompletion:(nullable void (^)(NSError *_Nullable error))completion;
+
 @end
 
 NS_ASSUME_NONNULL_END

Firestore/Swift/Tests/API/BasicCompileTests.swift

@@ -52,6 +52,8 @@ func main() {
 
   enableDisableNetwork(database: db)
 
+  clearPersistence(database: db)
+
   types()
 }
 
@@ -174,6 +176,15 @@ func enableDisableNetwork(database db: Firestore) {
   }
 }
 
+func clearPersistence(database db: Firestore) {
+  db.clearPersistence { error in
+    if let e = error {
+      print("Uh oh! \(e)")
+      return
+    }
+  }
+}
+
 func writeDocuments(at docRef: DocumentReference, database db: Firestore) {
   var batch: WriteBatch