Fix an issue around deleting records from the database. (#3926)

* Assign weakself to self.

* Add unit test.

* Style fixes.

* Address review comments.

* Review comments.

Author: dmandar

FirebaseRemoteConfig/Sources/RCNConfigDBManager.m

@@ -899,8 +899,12 @@ - (NSMutableDictionary *)loadMainTableWithBundleIdentifier:(NSString *)bundleIde
 - (void)deleteRecordFromMainTableWithNamespace:(NSString *)namespace_p
                               bundleIdentifier:(NSString *)bundleIdentifier
                                     fromSource:(RCNDBSource)source {
-  __weak RCNConfigDBManager *weakSelf;
+  __weak RCNConfigDBManager *weakSelf = self;
   dispatch_async(_databaseOperationQueue, ^{
+    RCNConfigDBManager *strongSelf = weakSelf;
+    if (!strongSelf) {
+      return;
+    }
     NSArray *params = @[ bundleIdentifier, namespace_p ];
     const char *SQL =
         "DELETE FROM " RCNTableNameMain " WHERE bundle_identifier = ? and namespace = ?";
@@ -909,42 +913,54 @@ - (void)deleteRecordFromMainTableWithNamespace:(NSString *)namespace_p
     } else if (source == RCNDBSourceActive) {
       SQL = "DELETE FROM " RCNTableNameMainActive " WHERE bundle_identifier = ? and namespace = ?";
     }
-    [weakSelf executeQuery:SQL withParams:params];
+    [strongSelf executeQuery:SQL withParams:params];
   });
 }
 
 - (void)deleteRecordWithBundleIdentifier:(NSString *)bundleIdentifier
                             isInternalDB:(BOOL)isInternalDB {
-  __weak RCNConfigDBManager *weakSelf;
+  __weak RCNConfigDBManager *weakSelf = self;
   dispatch_async(_databaseOperationQueue, ^{
+    RCNConfigDBManager *strongSelf = weakSelf;
+    if (!strongSelf) {
+      return;
+    }
     const char *SQL = "DELETE FROM " RCNTableNameInternalMetadata " WHERE key LIKE ?";
     if (!isInternalDB) {
       SQL = "DELETE FROM " RCNTableNameMetadata " WHERE bundle_identifier = ?";
     }
     NSArray *params = @[ bundleIdentifier ];
-    [weakSelf executeQuery:SQL withParams:params];
+    [strongSelf executeQuery:SQL withParams:params];
   });
 }
 
 - (void)deleteAllRecordsFromTableWithSource:(RCNDBSource)source {
-  __weak RCNConfigDBManager *weakSelf;
+  __weak RCNConfigDBManager *weakSelf = self;
   dispatch_async(_databaseOperationQueue, ^{
+    RCNConfigDBManager *strongSelf = weakSelf;
+    if (!strongSelf) {
+      return;
+    }
     const char *SQL = "DELETE FROM " RCNTableNameMain;
     if (source == RCNDBSourceDefault) {
       SQL = "DELETE FROM " RCNTableNameMainDefault;
     } else if (source == RCNDBSourceActive) {
       SQL = "DELETE FROM " RCNTableNameMainActive;
     }
-    [weakSelf executeQuery:SQL];
+    [strongSelf executeQuery:SQL];
   });
 }
 
 - (void)deleteExperimentTableForKey:(NSString *)key {
-  __weak RCNConfigDBManager *weakSelf;
+  __weak RCNConfigDBManager *weakSelf = self;
   dispatch_async(_databaseOperationQueue, ^{
+    RCNConfigDBManager *strongSelf = weakSelf;
+    if (!strongSelf) {
+      return;
+    }
     NSArray *params = @[ key ];
     const char *SQL = "DELETE FROM " RCNTableNameExperiment " WHERE key = ?";
-    [weakSelf executeQuery:SQL withParams:params];
+    [strongSelf executeQuery:SQL withParams:params];
   });
 }
 

FirebaseRemoteConfig/Tests/Unit/RCNConfigDBManagerTest.m

@@ -258,6 +258,88 @@ - (void)testWriteAndLoadMetadataResult {
                                }];
 }
 
+// Create a key each for two namespaces, delete it from one namespace, read both namespaces.
+- (void)testDeleteParamAndLoadMainTable {
+  XCTestExpectation *namespaceDeleteExpectation =
+      [self expectationWithDescription:@"Contents of 'namespace_delete' should be deleted."];
+  XCTestExpectation *namespaceKeepExpectation =
+      [self expectationWithDescription:@"Write a key to namespace_keep and read back again."];
+  NSString *namespaceToDelete = @"namespace_delete";
+  NSString *namespaceToKeep = @"namespace_keep";
+  NSString *bundleIdentifier = @"testBundleID";
+
+  // Write something to the database for both namespaces.
+  // Completion handler for the write to namespace_delete namespace.
+  RCNDBCompletion insertNamespace1Completion = ^void(BOOL success, NSDictionary *result) {
+    XCTAssertTrue(success);
+
+    // Delete the key for given namespace.
+    [_DBManager deleteRecordFromMainTableWithNamespace:namespaceToDelete
+                                      bundleIdentifier:bundleIdentifier
+                                            fromSource:RCNDBSourceActive];
+
+    // Read from the database and verify expected values.
+    [_DBManager
+        loadMainWithBundleIdentifier:bundleIdentifier
+                   completionHandler:^(BOOL success, NSDictionary *fetchedConfig,
+                                       NSDictionary *activeConfig, NSDictionary *defaultConfig) {
+                     NSMutableDictionary *res = [activeConfig mutableCopy];
+                     XCTAssertTrue(success);
+                     FIRRemoteConfigValue *value = res[namespaceToDelete][@"keyToDelete"];
+                     XCTAssertNil(value);
+
+                     FIRRemoteConfigValue *value2 = res[namespaceToKeep][@"keyToRetain"];
+                     XCTAssertTrue([value2.stringValue isEqualToString:@"valueToRetain"]);
+
+                     [namespaceDeleteExpectation fulfill];
+                   }];
+  };
+
+  // Insert a key into the second namespace.
+  RCNDBCompletion insertNamespace2Completion = ^void(BOOL success, NSDictionary *result) {
+    XCTAssertTrue(success);
+
+    // Ensure DB read succeeds.
+    [_DBManager
+        loadMainWithBundleIdentifier:bundleIdentifier
+                   completionHandler:^(BOOL success, NSDictionary *fetchedConfig,
+                                       NSDictionary *activeConfig, NSDictionary *defaultConfig) {
+                     NSMutableDictionary *res = [activeConfig mutableCopy];
+                     XCTAssertTrue(success);
+                     FIRRemoteConfigValue *value2 = res[namespaceToKeep][@"keyToRetain"];
+                     XCTAssertTrue([value2.stringValue isEqualToString:@"valueToRetain"]);
+
+                     [namespaceKeepExpectation fulfill];
+                   }];
+  };
+  // We will delete this key after storing in the database.
+  NSString *valueToDelete = @"valueToDelete";
+  NSString *keyToDelete = @"keyToDelete";
+  NSArray *items = @[
+    bundleIdentifier, namespaceToDelete, keyToDelete,
+    [valueToDelete dataUsingEncoding:NSUTF8StringEncoding]
+  ];
+  [_DBManager insertMainTableWithValues:items
+                             fromSource:RCNDBSourceActive
+                      completionHandler:insertNamespace1Completion];
+
+  // This key value will be retained.
+  NSString *valueToRetain = @"valueToRetain";
+  NSString *keyToRetain = @"keyToRetain";
+  NSArray *items2 = @[
+    bundleIdentifier, namespaceToKeep, keyToRetain,
+    [valueToRetain dataUsingEncoding:NSUTF8StringEncoding]
+  ];
+  [_DBManager insertMainTableWithValues:items2
+                             fromSource:RCNDBSourceActive
+                      completionHandler:insertNamespace2Completion];
+
+  [self waitForExpectationsWithTimeout:_expectionTimeout
+                               handler:^(NSError *error) {
+                                 XCTAssertNil(error);
+                               }];
+}
+
 - (void)testWriteAndLoadExperiments {
   XCTestExpectation *updateAndLoadExperimentExpectation =
       [self expectationWithDescription:@"Update and load experiment in database successfully"];