feat(logging): add public log listener methods

* Adds the following new public methods:
   - OneSignal.Debug.addLogListener
   - OneSignal.Debug.removeLogListener
* These new methods provide a way to capture all SDK log entires at runtime, allowing the app developer to store these and/or send them to their server.
* The log listener is independent of logLevel, all message are always sent to listeners.
* Use the new `OSCopyOnWriteSet`: it is possible for someone to add or remove a log listener within the `onLogEvent` callback, thus modifying the set of listeners as the set is being enumerated. @synchronized is a recursive lock, so it would not be sufficient. Locking the entire set of listeners would result in deadlock.
* This mimics the Android implementation which uses the built-in `CopyOnWriteArraySet`

Author: nan-li

iOS_SDK/OneSignalSDK/OneSignal.xcodeproj/project.pbxproj

@@ -2619,9 +2619,9 @@
 				4529DF0B1FA932AC00CEAB1D /* OneSignalTrackFirebaseAnalytics.m */,
 				DE7D1831270279D9002D3A5D /* OSNotificationClasses.h */,
 				DE7D183527027AA0002D3A5D /* OneSignalLog.h */,
+				DE7D183327027A73002D3A5D /* OneSignalLog.m */,
 				3CCF44BC299B17290021964D /* OneSignalWrapper.h */,
 				3CCF44BD299B17290021964D /* OneSignalWrapper.m */,
-				DE7D183327027A73002D3A5D /* OneSignalLog.m */,
 				DE7D187627037A16002D3A5D /* OneSignalCoreHelper.h */,
 				DE7D187827037A26002D3A5D /* OneSignalCoreHelper.m */,
 				7AE28B8725B8ADF400529100 /* OSMacros.h */,

iOS_SDK/OneSignalSDK/OneSignalCore/Source/OneSignalLog.h

@@ -36,9 +36,40 @@ typedef NS_ENUM(NSUInteger, ONE_S_LOG_LEVEL) {
     ONE_S_LL_VERBOSE
 };
 
+@interface OneSignalLogEvent : NSObject
+@property(readonly)ONE_S_LOG_LEVEL level;
+@property(readonly, nonnull)NSString *entry;
+@end
+
+@protocol OSLogListener <NSObject>
+- (void)onLogEvent:(OneSignalLogEvent *_Nonnull)event;
+@end
+
 @protocol OSDebug <NSObject>
+/**
+ The log level the OneSignal SDK should be writing to the Xcode log. Defaults to [LogLevel.WARN].
+ 
+ WARNING: This should not be set higher than LogLevel.WARN in a production setting.
+ */
 + (void)setLogLevel:(ONE_S_LOG_LEVEL)logLevel;
+/**
+ The log level the OneSignal SDK should be showing as a modal. Defaults to [LogLevel.NONE].
+ 
+ WARNING: This should not be used in a production setting.
+ */
 + (void)setAlertLevel:(ONE_S_LOG_LEVEL)logLevel NS_REFINED_FOR_SWIFT;
+/**
+ Add a listener to receive all logging messages the SDK produces.
+ Useful to capture and send logs to your server.
+ 
+ NOTE: All log messages are always passed, LogLevel has no effect on this.
+ */
++ (void)addLogListener:(NSObject<OSLogListener>*_Nonnull)listener NS_REFINED_FOR_SWIFT;
+/**
+ Removes a listener added by addLogListener
+ */
++ (void)removeLogListener:(NSObject<OSLogListener>*_Nonnull)listener NS_REFINED_FOR_SWIFT;
+
 @end
 
 @interface OneSignalLog : NSObject<OSDebug>

iOS_SDK/OneSignalSDK/OneSignalCore/Source/OneSignalLog.m

@@ -28,6 +28,15 @@
 #import <Foundation/Foundation.h>
 #import "OneSignalLog.h"
 #import "OSDialogInstanceManager.h"
+#import "OSCopyOnWriteSet.h"
+
+@implementation OneSignalLogEvent
+- (instancetype)initWithLevel:(ONE_S_LOG_LEVEL)level entry:(NSString*)entry {
+    _level = level;
+    _entry = entry;
+    return self;
+}
+@end
 
 @implementation OneSignalLog
 
@@ -38,6 +47,15 @@ @implementation OneSignalLog
     return self;
 }
 
++ (OSCopyOnWriteSet<NSObject<OSLogListener> *>*)logListeners {
+    static OSCopyOnWriteSet<NSObject<OSLogListener> *> *_logListeners;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        _logListeners = [OSCopyOnWriteSet new];
+    });
+    return _logListeners;
+}
+
 + (void)setLogLevel:(ONE_S_LOG_LEVEL)nsLogLevel {
     _nsLogLevel = nsLogLevel;
 }
@@ -46,6 +64,14 @@ + (void)setAlertLevel:(ONE_S_LOG_LEVEL)logLevel {
     _alertLogLevel = logLevel;
 }
 
++ (void)addLogListener:(NSObject<OSLogListener>*_Nonnull)listener {
+    [self.logListeners addObject:listener];
+}
+
++ (void)removeLogListener:(NSObject<OSLogListener>*_Nonnull)listener {
+    [self.logListeners removeObject:listener];
+}
+
 + (void)onesignalLog:(ONE_S_LOG_LEVEL)logLevel message:(NSString* _Nonnull)message {
     onesignal_Log(logLevel, message);
 }
@@ -86,6 +112,13 @@ void onesignal_Log(ONE_S_LOG_LEVEL logLevel, NSString* message) {
     if (logLevel <= _alertLogLevel) {
         [[OSDialogInstanceManager sharedInstance] presentDialogWithTitle:levelString withMessage:message withActions:nil cancelTitle:NSLocalizedString(@"Close", @"Close button") withActionCompletion:nil];
     }
+
+    for (NSObject<OSLogListener> *listener in OneSignalLog.logListeners.allObjects) {
+        if ([listener respondsToSelector:@selector(onLogEvent:)]) {
+            OneSignalLogEvent *event = [[OneSignalLogEvent alloc] initWithLevel:logLevel entry:[levelString stringByAppendingString:message]];
+            [listener onLogEvent:event];
+        }
+    }
 }
 
 @end

iOS_SDK/OneSignalSDK/Source/OneSignalSwiftInterface.swift

@@ -63,9 +63,29 @@ public extension OneSignal {
 }
 
 public extension OSDebug {
+    /**
+     The log level the OneSignal SDK should be showing as a modal. Defaults to [LogLevel.NONE].
+     
+     WARNING: This should not be used in a production setting.
+     */
     static func setAlertLevel(_ logLevel: ONE_S_LOG_LEVEL) {
         __setAlert(logLevel)
     }
+    /**
+     Add a listener to receive all logging messages the SDK produces.
+     Useful to capture and send logs to your server.
+     
+     NOTE: All log messages are always passed, LogLevel has no effect on this.
+     */
+    static func addLogListener(_ listener: OSLogListener) {
+        __add(listener)
+    }
+    /**
+     Removes a listener added by addLogListener
+     */
+    static func removeLogListener(_ listener: OSLogListener) {
+        __remove(listener)
+    }
 }
 
 public extension OSInAppMessages {