Add Send Failure Callback API

Bugsnag/BugsnagInternals.h

@@ -112,6 +112,8 @@ typedef void (^ BSGClientObserver)(BSGClientObserverEvent event, _Nullable id va
 
 @property (nonatomic) NSMutableArray<BugsnagOnSendErrorBlock> *onSendBlocks;
 
+@property (nonatomic) NSMutableArray<BugsnagOnSendFailureBlock> *onFailureBlocks;
+
 @property (nonatomic) NSMutableArray<BugsnagOnSessionBlock> *onSessionBlocks;
 
 @end

Bugsnag/Configuration/BugsnagConfiguration.m

@@ -119,6 +119,7 @@ - (nonnull id)copyWithZone:(nullable NSZone *)zone {
     // as creating a copy of the array would prevent this
     [copy setOnBreadcrumbBlocks:self.onBreadcrumbBlocks];
     [copy setOnSendBlocks:self.onSendBlocks];
+    [copy setOnFailureBlocks:self.onFailureBlocks];
     [copy setOnSessionBlocks:self.onSessionBlocks];
     [copy setTelemetry:self.telemetry];
     return copy;
@@ -174,6 +175,7 @@ - (instancetype)initWithApiKey:(NSString *)apiKey {
     _appHangThresholdMillis = BugsnagAppHangThresholdFatalOnly;
 #endif
     _onSendBlocks = [NSMutableArray new];
+    _onFailureBlocks = [NSMutableArray new];
     _onSessionBlocks = [NSMutableArray new];
     _onBreadcrumbBlocks = [NSMutableArray new];
     _plugins = [NSMutableSet new];
@@ -284,6 +286,24 @@ - (NSURLSession *)sessionOrDefault {
     return session ? session : getConfigDefaultURLSession();
 }
 
+// =============================================================================
+// MARK: - onSendFailure
+// =============================================================================
+
+- (BugsnagOnSendFailureRef)addOnSendFailureBlock:(BugsnagOnSendFailureBlock)block {
+    BugsnagOnSendFailureBlock callback = [block copy];
+    [self.onFailureBlocks addObject:callback];
+    return callback;
+}
+
+- (void)removeOnSendFailure:(BugsnagOnSendFailureRef)callback {
+    if (![callback isKindOfClass:NSClassFromString(@"NSBlock")]) {
+        bsg_log_err(@"Invalid object type passed to %@", NSStringFromSelector(_cmd));
+        return;
+    }
+    [self.onFailureBlocks removeObject:(id)callback];
+}
+
 // =============================================================================
 // MARK: - onSendBlock
 // =============================================================================

Bugsnag/Delivery/BSGEventUploadOperation.m

@@ -46,22 +46,36 @@ - (instancetype)initWithDelegate:(id<BSGEventUploadOperationDelegate>)delegate {
     return self;
 }
 
+- (void)_sendFailureForEvent:(BugsnagEvent *)event configuration:(BugsnagConfiguration *)configuration {
+    NSArray<BugsnagOnSendFailureBlock> *failureBlocks = [configuration.onFailureBlocks copy];
+    for (BugsnagOnSendFailureBlock block in failureBlocks) {
+        @try {
+            block(event);
+        } @catch (NSException *exception) {
+            bsg_log_err(@"Ignoring exception thrown by onFailure callback: %@", exception);
+        }
+    }
+}
+
 - (void)runWithDelegate:(id<BSGEventUploadOperationDelegate>)delegate completionHandler:(nonnull void (^)(void))completionHandler {
     bsg_log_debug(@"Preparing event %@", self.name);
 
+    BugsnagConfiguration *configuration = delegate.configuration;
+
     NSError *error = nil;
     BugsnagEvent *event = [self loadEventAndReturnError:&error];
     if (!event) {
         bsg_log_err(@"Failed to load event %@ due to error %@", self.name, error);
         if (!(error.domain == NSCocoaErrorDomain && error.code == NSFileReadNoSuchFileError)) {
             [self deleteEvent];
+            // If this happens, there will be no event, but at least we'll notify
+            // the client that an event wasn't sent.
+            [self _sendFailureForEvent:event configuration:configuration];
         }
         completionHandler();
         return;
     }
 
-    BugsnagConfiguration *configuration = delegate.configuration;
-
     if (!configuration.shouldSendReports || ![event shouldBeSent]) {
         bsg_log_info(@"Discarding event %@ because releaseStage not in enabledReleaseStages", self.name);
         [self deleteEvent];
@@ -107,6 +121,7 @@ - (void)runWithDelegate:(id<BSGEventUploadOperationDelegate>)delegate completion
          [NSString stringWithFormat:@"BSGEventUploadOperation -[runWithDelegate:completionHandler:] %@ %@",
           exception.name, exception.reason]];
         [self deleteEvent];
+        [self _sendFailureForEvent:event configuration:configuration];
         completionHandler();
         return;
     }
@@ -135,6 +150,7 @@ - (void)runWithDelegate:(id<BSGEventUploadOperationDelegate>)delegate completion
     if (!data) {
         bsg_log_debug(@"Encoding failed; will discard event %@", self.name);
         [self deleteEvent];
+        [self _sendFailureForEvent:event configuration:configuration];
         completionHandler();
         return;
     }
@@ -154,6 +170,7 @@ - (void)runWithDelegate:(id<BSGEventUploadOperationDelegate>)delegate completion
              [NSString stringWithFormat:@"BSGEventUploadOperation -[runWithDelegate:completionHandler:] %@ %@",
               exception.name, exception.reason]];
             [self deleteEvent];
+            [self _sendFailureForEvent:event configuration:configuration];
             completionHandler();
             return;
         }
@@ -174,6 +191,7 @@ - (void)runWithDelegate:(id<BSGEventUploadOperationDelegate>)delegate completion
             case BSGDeliveryStatusUndeliverable:
                 bsg_log_debug(@"Upload failed; will discard event %@", self.name);
                 [self deleteEvent];
+                [self _sendFailureForEvent:event configuration:configuration];
                 break;
         }
 

Bugsnag/Helpers/BSGTelemetry.m

@@ -116,6 +116,7 @@ static BOOL IsStaticallyLinked(void) {
     callbacks[@"onBreadcrumb"] = IntegerValue(configuration.onBreadcrumbBlocks.count, 0);
     callbacks[@"onCrashHandler"] = configuration.onCrashHandler ? @1 : nil;
     callbacks[@"onSendError"] = IntegerValue(configuration.onSendBlocks.count, 0);
+    callbacks[@"onFailure"] = IntegerValue(configuration.onFailureBlocks.count, 0);
     callbacks[@"onSession"] = IntegerValue(configuration.onSessionBlocks.count, 0);
 
     return @{

Bugsnag/include/Bugsnag/BugsnagConfiguration.h

@@ -114,6 +114,18 @@ typedef BOOL (^BugsnagOnSendErrorBlock)(BugsnagEvent *_Nonnull event);
  */
 typedef id<NSObject> BugsnagOnSendErrorRef;
 
+/**
+ *  A configuration block for being notified when an event fails to send.
+ *
+ *  @param event The event report. NULL if the event cannot be loaded from disk.
+ */
+typedef void (^BugsnagOnSendFailureBlock)(BugsnagEvent *_Nullable event);
+
+/**
+ * An opaque object that identifies and allows the removal of a BugsnagOnSendFailureBlock.
+ */
+typedef id<NSObject> BugsnagOnSendFailureRef;
+
 /**
  *  A configuration block for modifying a captured breadcrumb
  *
@@ -441,6 +453,29 @@ BUGSNAG_EXTERN
     BUGSNAG_DEPRECATED_WITH_REPLACEMENT("removeOnSession:")
     NS_SWIFT_NAME(removeOnSession(block:));
 
+// =============================================================================
+// MARK: - onSendFailure
+// =============================================================================
+
+/**
+ *  Add a callback to be invoked when a report fails to be
+ *  send to Bugsnag.
+ *
+ *  @param block A block to be called on send failure.
+ *
+ *  @returns An opaque reference to the callback which can be passed to `removeOnSendFailure:`
+ */
+- (BugsnagOnSendFailureRef)addOnSendFailureBlock:(BugsnagOnSendFailureBlock)block
+NS_SWIFT_NAME(addOnSendFailure(block:));
+
+/**
+ * Remove the callback that would be invoked on send failure.
+ *
+ * @param callback The opaque reference of the callback, returned by `addOnSendFailureBlock:`
+ */
+- (void)removeOnSendFailure:(BugsnagOnSendFailureRef)callback
+NS_SWIFT_NAME(removeOnSendFailure(_:));
+
 // =============================================================================
 // MARK: - onSend
 // =============================================================================

CHANGELOG.md

@@ -1,6 +1,11 @@
 Changelog
 =========
 
+### Enhancements
+
+* Add callback for when an Error fails to send.
+  []()
+
 ## 6.30.2 (2024-11-07)
 
 ### Bug Fixes

Tests/BugsnagTests/BugsnagConfigurationTests.m

@@ -803,25 +803,44 @@ -(void)testCrashTypeMapping {
 #endif
 
 /**
- * Test that removeOnSendBlock() performs as expected.
- * Note: We don't test that set blocks are executed since this is tested elsewhere
- * (e.g. in BugsnagBreadcrumbsTest)
+ * Test that removeOnFailureBlock() performs as expected.
  */
-- (void) testRemoveOnSendBlock {
+- (void) testRemoveOnFailureBlock {
     // Prevent sending events
     BugsnagConfiguration *configuration = [[BugsnagConfiguration alloc] initWithApiKey:DUMMY_APIKEY_32CHAR_1];
     XCTAssertEqual([[configuration onSendBlocks] count], 0);
-
-    BugsnagOnSendErrorBlock block = ^BOOL(BugsnagEvent * _Nonnull event) { return false; };
-
-    BugsnagOnSendErrorRef callback = [configuration addOnSendErrorBlock:block];
+    
+    BugsnagOnSendFailureBlock block = ^(BugsnagEvent * _Nonnull event) {};
+    
+    BugsnagOnSendFailureRef callback = [configuration addOnSendFailureBlock:block];
     BugsnagClient *client = [[BugsnagClient alloc] initWithConfiguration:configuration];
     [client start];
+
+    XCTAssertEqual([[configuration onFailureBlocks] count], 1);
+
+    [configuration removeOnSendFailure:callback];
+    XCTAssertEqual([[configuration onFailureBlocks] count], 0);
+}
 
-    XCTAssertEqual([[configuration onSendBlocks] count], 1);
-
-    [configuration removeOnSendError:callback];
-    XCTAssertEqual([[configuration onSendBlocks] count], 0);
+/**
+ * Test that clearOnSendFailureBlock() performs as expected.
+ */
+- (void) testClearOnSendFailureBlock {
+    // Prevent sending events
+    BugsnagConfiguration *configuration = [[BugsnagConfiguration alloc] initWithApiKey:DUMMY_APIKEY_32CHAR_1];
+    XCTAssertEqual([[configuration onFailureBlocks] count], 0);
+
+    BugsnagOnSendFailureBlock block1 = ^(BugsnagEvent * _Nonnull event) {};
+    BugsnagOnSendFailureBlock block2 = ^(BugsnagEvent * _Nonnull event) {};
+
+    // Add more than one
+    [configuration addOnSendFailureBlock:block1];
+    [configuration addOnSendFailureBlock:block2];
+
+    BugsnagClient *client = [[BugsnagClient alloc] initWithConfiguration:configuration];
+    [client start];
+
+    XCTAssertEqual([[configuration onFailureBlocks] count], 2);
 }
 
 /**
@@ -845,6 +864,28 @@ - (void) testClearOnSendBlock {
     XCTAssertEqual([[configuration onSendBlocks] count], 2);
 }
 
+/**
+ * Test that removeOnSendBlock() performs as expected.
+ * Note: We don't test that set blocks are executed since this is tested elsewhere
+ * (e.g. in BugsnagBreadcrumbsTest)
+ */
+- (void) testRemoveOnSendBlock {
+    // Prevent sending events
+    BugsnagConfiguration *configuration = [[BugsnagConfiguration alloc] initWithApiKey:DUMMY_APIKEY_32CHAR_1];
+    XCTAssertEqual([[configuration onSendBlocks] count], 0);
+
+    BugsnagOnSendErrorBlock block = ^BOOL(BugsnagEvent * _Nonnull event) { return false; };
+
+    BugsnagOnSendErrorRef callback = [configuration addOnSendErrorBlock:block];
+    BugsnagClient *client = [[BugsnagClient alloc] initWithConfiguration:configuration];
+    [client start];
+
+    XCTAssertEqual([[configuration onSendBlocks] count], 1);
+
+    [configuration removeOnSendError:callback];
+    XCTAssertEqual([[configuration onSendBlocks] count], 0);
+}
+
 - (void)testSendThreadsDefault {
 #if !TARGET_OS_WATCH
     BugsnagConfiguration *config = [[BugsnagConfiguration alloc] initWithApiKey:DUMMY_APIKEY_32CHAR_1];
@@ -878,6 +919,12 @@ - (void)testNSCopying {
     NSArray *sendBlocks = @[ onSendBlock1, onSendBlock2 ];
     [config setOnSendBlocks:[sendBlocks mutableCopy]]; // Mutable arg required
 
+    BugsnagOnSendFailureBlock onFailureBlock1 = ^(BugsnagEvent * _Nonnull event) {};
+    BugsnagOnSendFailureBlock onFailureBlock2 = ^(BugsnagEvent * _Nonnull event) {};
+
+    NSArray *failureBlocks = @[ onFailureBlock1, onFailureBlock2 ];
+    [config setOnFailureBlocks:[failureBlocks mutableCopy]]; // Mutable arg required
+
     // Clone
     BugsnagConfiguration *clone = [config copy];
     XCTAssertNotEqual(config, clone);
@@ -919,6 +966,12 @@ - (void)testNSCopying {
     [clone setOnSendBlocks:[@[ onSendBlock2 ] mutableCopy]];
     XCTAssertNotEqual(config.onSendBlocks[0], clone.onSendBlocks[0]);
 
+    // Array (of blocks)
+    XCTAssertEqual(config.onFailureBlocks, clone.onFailureBlocks);
+    XCTAssertEqual(config.onFailureBlocks[0], clone.onFailureBlocks[0]);
+    [clone setOnFailureBlocks:[@[ onFailureBlock2 ] mutableCopy]];
+    XCTAssertNotEqual(config.onFailureBlocks[0], clone.onFailureBlocks[0]);
+
     XCTAssertEqualObjects(clone.notifier.name, config.notifier.name);
     XCTAssertEqualObjects(clone.notifier.version, config.notifier.version);
     XCTAssertEqualObjects(clone.notifier.url, config.notifier.url);

Tests/BugsnagTests/BugsnagSwiftConfigurationTests.swift

@@ -20,6 +20,29 @@ class BugsnagSwiftConfigurationTests: BSGTestCase {
         XCTAssertEqual(config.apiKey, DUMMY_APIKEY_16CHAR)
     }
 
+    func testRemoveOnFailureError() {
+        let config = BugsnagConfiguration(DUMMY_APIKEY_16CHAR)
+        let onFailureBlocks: NSMutableArray = config.value(forKey: "onFailureBlocks") as! NSMutableArray
+        XCTAssertEqual(onFailureBlocks.count, 0)
+
+        let onFailureError = config.addOnSendFailure { _ in }
+        XCTAssertEqual(onFailureBlocks.count, 1)
+
+        config.removeOnSendFailure(onFailureError)
+        XCTAssertEqual(onFailureBlocks.count, 0)
+    }
+
+    func testRemoveInvalidOnFailureDoesNotCrash() {
+        let config = BugsnagConfiguration(DUMMY_APIKEY_16CHAR)
+        let onSendFailureBlock: (BugsnagEvent?) -> Void = { _ in }
+        config.addOnSendFailure(block: onSendFailureBlock)
+
+        // This does not compile:
+        // config.removeOnSendFailure(onSendErrorBlock)
+
+        config.removeOnSendFailure("" as NSString)
+    }
+
     func testRemoveOnSendError() {
         let config = BugsnagConfiguration(DUMMY_APIKEY_16CHAR)
         let onSendBlocks: NSMutableArray = config.value(forKey: "onSendBlocks") as! NSMutableArray

Tests/BugsnagTests/ConfigurationApiValidationTest.m

@@ -225,6 +225,14 @@ - (void)testValidOnSessionBlock {
     XCTAssertEqual(0, [self.config.onSessionBlocks count]);
 }
 
+- (void)testValidOnSendFailureBlock {
+    void (^block)(BugsnagEvent *) = ^(BugsnagEvent *event) {};
+    BugsnagOnSendFailureRef callback = [self.config addOnSendFailureBlock:block];
+    XCTAssertEqual(1, [self.config.onFailureBlocks count]);
+    [self.config removeOnSendFailure:callback];
+    XCTAssertEqual(0, [self.config.onFailureBlocks count]);
+}
+
 - (void)testValidOnSendErrorBlock {
     BOOL (^block)(BugsnagEvent *) = ^BOOL(BugsnagEvent *event) {
         return NO;