fix(sessions): Missing mechanism.handled is not considered crash (#3353)

Some events have mechanism.handled missing in events.exceptions.values and those events should not crash the session.

This happens for example in Flutter.

Author: krystofwoldrich

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixes
+
+- Missing `mechanism.handled` is not considered crash (#3353)
+
 ## 8.14.1
 
 ### Fixes

Sources/Sentry/SentryHub.m

@@ -642,22 +642,22 @@ - (BOOL)envelopeContainsEventWithErrorOrHigher:(NSArray<SentryEnvelopeItem *> *)
 
             SentryLevel level = sentryLevelForString(eventJson[@"level"]);
             if (level >= kSentryLevelError) {
-                *handled = [self eventContainsUnhandledError:eventJson];
+                *handled = [self eventContainsOnlyHandledErrors:eventJson];
                 return YES;
             }
         }
     }
     return NO;
 }
 
-- (BOOL)eventContainsUnhandledError:(NSDictionary *)eventDictionary
+- (BOOL)eventContainsOnlyHandledErrors:(NSDictionary *)eventDictionary
 {
     NSArray *exceptions = eventDictionary[@"exception"][@"values"];
     for (NSDictionary *exception in exceptions) {
         NSDictionary *mechanism = exception[@"mechanism"];
         NSNumber *handled = mechanism[@"handled"];
 
-        if ([handled boolValue] == NO) {
+        if (handled != nil && [handled boolValue] == NO) {
             return NO;
         }
     }

Tests/SentryTests/SentryHubTests.swift

@@ -2,6 +2,7 @@ import Sentry
 import SentryTestUtils
 import XCTest
 
+// swiftlint:disable file_length
 class SentryHubTests: XCTestCase {
 
     private static let dsnAsString = TestConstants.dsnAsString(username: "SentryHubTests")
@@ -656,6 +657,14 @@ class SentryHubTests: XCTestCase {
         assertSessionWithIncrementedErrorCountedAdded()
     }
 
+    func testCaptureEnvelope_WithEventWithoutExceptionMechanism() {
+        sut.startSession()
+        
+        captureFatalEventWithoutExceptionMechanism()
+        
+        assertSessionWithIncrementedErrorCountedAdded()
+    }
+    
     func testCaptureEnvelope_WithEventWithFatal() {
         sut.startSession()
 
@@ -864,12 +873,49 @@ class SentryHubTests: XCTestCase {
         group.wait()
     }
 
+    func testEventContainsOnlyHandledErrors() {
+        let sut = fixture.getSut()
+        XCTAssertFalse(sut.eventContainsOnlyHandledErrors(["exception":
+                                                            ["values":
+                                                                [["mechanism": ["handled": false]]]
+                                                            ]
+                                                          ]))
+        
+        XCTAssertTrue(sut.eventContainsOnlyHandledErrors(["exception":
+                                                            ["values":
+                                                                [["mechanism": ["handled": true]],
+                                                                 ["mechanism": ["handled": true]]]
+                                                            ]
+                                                         ]))
+        
+        XCTAssertFalse(sut.eventContainsOnlyHandledErrors(["exception":
+                                                            ["values":
+                                                                [["mechanism": ["handled": true]],
+                                                                 ["mechanism": ["handled": false]]]
+                                                            ]
+                                                          ]))
+        
+        XCTAssertTrue(sut.eventContainsOnlyHandledErrors(["exception":
+                                                            ["values":
+                                                                [["mechanism": ["handled": true]],
+                                                                 ["mechanism": ["other-key": false]]]
+                                                            ]
+                                                         ]))
+    }
+    
     private func captureEventEnvelope(level: SentryLevel) {
         let event = TestData.event
         event.level = level
         sut.capture(SentryEnvelope(event: event))
     }
 
+    private func captureFatalEventWithoutExceptionMechanism() {
+        let event = TestData.event
+        event.level = SentryLevel.fatal
+        event.exceptions?[0].mechanism = nil
+        sut.capture(SentryEnvelope(event: event))
+    }
+    
     private func givenCrashedSession() {
         fixture.sentryCrash.internalCrashedLastLaunch = true
         fixture.fileManager.storeCrashedSession(fixture.crashedSession)

Tests/SentryTests/State/SentryHub+Test.h

@@ -16,6 +16,7 @@ SentryHub ()
 - (NSArray<id<SentryIntegrationProtocol>> *)installedIntegrations;
 - (NSSet<NSString *> *)installedIntegrationNames;
 
+- (BOOL)eventContainsOnlyHandledErrors:(NSDictionary *)eventDictionary;
 @end
 
 NS_ASSUME_NONNULL_END