fix(app-start): accessing null json fields from fetchNativeAppStart

CHANGELOG.md

@@ -21,6 +21,7 @@
 - Rounding error used on frames.total and reject frame measurements if frames.total is less than frames.slow or frames.frozen ([#2308](https://github.com/getsentry/sentry-dart/pull/2308))
 - iOS replay integration when only `onErrorSampleRate` is specified ([#2306](https://github.com/getsentry/sentry-dart/pull/2306))
 - Fix TTID timing issue ([#2326](https://github.com/getsentry/sentry-dart/pull/2326))
+- Accessing invalid json fields from `fetchNativeAppStart` should return null ([#2340](https://github.com/getsentry/sentry-dart/pull/2340))
 
 ### Deprecate
 

flutter/lib/src/native/native_app_start.dart

@@ -1,4 +1,5 @@
 import 'package:meta/meta.dart';
+import 'package:sentry/sentry.dart';
 
 @internal
 class NativeAppStart {
@@ -13,12 +14,29 @@ class NativeAppStart {
   bool isColdStart;
   Map<dynamic, dynamic> nativeSpanTimes;
 
-  factory NativeAppStart.fromJson(Map<String, dynamic> json) {
+  static NativeAppStart? fromJson(Map<String, dynamic> json) {
+    final appStartTime = json['appStartTime'];
+    final pluginRegistrationTime = json['pluginRegistrationTime'];
+    final isColdStart = json['isColdStart'];
+    final nativeSpanTimes = json['nativeSpanTimes'];
+
+    if (appStartTime is! double ||
+        pluginRegistrationTime is! int ||
+        isColdStart is! bool ||
+        nativeSpanTimes is! Map) {
+      // ignore: invalid_use_of_internal_member
+      Sentry.currentHub.options.logger(
+        SentryLevel.warning,
+        'Failed to parse json when capturing App Start metrics. App Start wont be reported.',
+      );
+      return null;
+    }
+
     return NativeAppStart(
-      appStartTime: json['appStartTime'] as double,
-      pluginRegistrationTime: json['pluginRegistrationTime'] as int,
-      isColdStart: json['isColdStart'] as bool,
-      nativeSpanTimes: json['nativeSpanTimes'] as Map<dynamic, dynamic>,
+      appStartTime: appStartTime,
+      pluginRegistrationTime: pluginRegistrationTime,
+      isColdStart: isColdStart,
+      nativeSpanTimes: nativeSpanTimes,
     );
   }
 }

flutter/test/sentry_native_channel_test.dart

@@ -52,6 +52,21 @@ void main() {
         expect(actual?.isColdStart, true);
       });
 
+      test('invalid fetchNativeAppStart returns null', () async {
+        when(channel.invokeMethod('fetchNativeAppStart'))
+            .thenAnswer((_) async => {
+                  'pluginRegistrationTime': 'invalid',
+                  'appStartTime': 'invalid',
+                  'isColdStart': 'invalid',
+                  // ignore: inference_failure_on_collection_literal
+                  'nativeSpanTimes': 'invalid',
+                });
+
+        final actual = await sut.fetchNativeAppStart();
+
+        expect(actual, isNull);
+      });
+
       test('beginNativeFrames', () async {
         when(channel.invokeMethod('beginNativeFrames'))
             .thenAnswer((realInvocation) async {});