Fix RCNConfigRealtime crash. (#14518)

Co-authored-by: Nick Cooke <36927374+ncooke3@users.noreply.github.com>

Author: tusharkhandelwal8

FirebaseRemoteConfig/CHANGELOG.md

@@ -2,6 +2,7 @@
 - [fixed] Codable APIs now accept optional `FirebaseDataEncoder` and
   `FirebaseDataDecoder` parameters, allowing for customization of
   encoding/decoding behavior. (#14368)
+- [fixed] Fix intermittent `RCNConfigRealtime` crash due to incorrect parsing of fragmented JSON. (#14518)
 
 # 11.9.0
 - [fixed] Mark internal `fetchSession` property as `atomic` to prevent a concurrency

FirebaseRemoteConfig/Sources/RCNConfigRealtime.m

@@ -573,20 +573,27 @@ - (void)URLSession:(NSURLSession *)session
     return;
   }
 
-  NSRange endRange = [strData rangeOfString:@"}"];
   NSRange beginRange = [strData rangeOfString:@"{"];
-  if (beginRange.location != NSNotFound && endRange.location != NSNotFound) {
-    FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000015",
-                @"Received config update message on stream.");
-    NSRange msgRange =
-        NSMakeRange(beginRange.location, endRange.location - beginRange.location + 1);
-    strData = [strData substringWithRange:msgRange];
-    data = [strData dataUsingEncoding:NSUTF8StringEncoding];
-    NSDictionary *response = [NSJSONSerialization JSONObjectWithData:data
-                                                             options:NSJSONReadingMutableContainers
-                                                               error:&dataError];
-
-    [self evaluateStreamResponse:response error:dataError];
+  if (beginRange.location != NSNotFound) {
+    NSRange endRange =
+        [strData rangeOfString:@"}"
+                       options:0
+                         range:NSMakeRange(beginRange.location + 1,
+                                           strData.length - beginRange.location - 1)];
+    if (endRange.location != NSNotFound) {
+      FIRLogDebug(kFIRLoggerRemoteConfig, @"I-RCN000015",
+                  @"Received config update message on stream.");
+      NSRange msgRange =
+          NSMakeRange(beginRange.location, endRange.location - beginRange.location + 1);
+      strData = [strData substringWithRange:msgRange];
+      data = [strData dataUsingEncoding:NSUTF8StringEncoding];
+      NSDictionary *response =
+          [NSJSONSerialization JSONObjectWithData:data
+                                          options:NSJSONReadingMutableContainers
+                                            error:&dataError];
+
+      [self evaluateStreamResponse:response error:dataError];
+    }
   }
 }
 

FirebaseRemoteConfig/Tests/Unit/RCNRemoteConfigTest.m

@@ -1834,6 +1834,31 @@ - (void)testFetchAndActivateRolloutsNotifyInterop {
   [self waitForExpectations:@[ notificationExpectation ] timeout:_expectationTimeout];
 }
 
+- (void)testURLSessionDelegateHandlesChunkedJSON {
+  NSString *testString = @"} {\"testKey\":\"testValue\"}";
+  NSData *testData = [testString dataUsingEncoding:NSUTF8StringEncoding];
+
+  NSMutableArray<XCTestExpectation *> *expectations =
+      [[NSMutableArray alloc] initWithCapacity:RCNTestRCNumTotalInstances];
+  for (int i = 0; i < RCNTestRCNumTotalInstances; i++) {
+    expectations[i] = [self
+        expectationWithDescription:
+            [NSString
+                stringWithFormat:@"Test delegate method handling chunked JSON - instance %d", i]];
+
+    NSURLSession *networkSession = [_configFetch[i] currentNetworkSession];
+    NSURLSessionDataTask *dataTask = [_configFetch[i] URLSessionDataTaskWithContent:[OCMArg any]
+                                                                    fetchTypeHeader:[OCMArg any]
+                                                                  completionHandler:nil];
+
+    XCTAssertNoThrow([_configRealtime[i] URLSession:networkSession
+                                           dataTask:dataTask
+                                     didReceiveData:testData]);
+    [expectations[i] fulfill];
+  }
+  [self waitForExpectationsWithTimeout:_expectationTimeout handler:nil];
+}
+
 - (void)testSetCustomSignals {
   NSMutableArray<XCTestExpectation *> *expectations =
       [[NSMutableArray alloc] initWithCapacity:RCNTestRCNumTotalInstances];