Refactored RCTLog and added facility to prepend extra data to the log message

Examples/UIExplorer/UIExplorer/Images.xcassets/story-background.imageset/Contents.json

@@ -1,5 +1,9 @@
 {
   "images" : [
+    {
+      "idiom" : "universal",
+      "scale" : "1x"
+    },
     {
       "idiom" : "universal",
       "scale" : "2x",

Libraries/Animation/RCTAnimationExperimentalManager.m

@@ -71,7 +71,7 @@
 
     UIView *view = viewRegistry[reactTag];
     if (!view) {
-      RCTLogWarn(@"React tag %@ is not registered with the view registry", reactTag);
+      RCTLogWarn(@"React tag #%@ is not registered with the view registry", reactTag);
       return;
     }
 

Libraries/RCTWebSocketDebugger/RCTWebSocketExecutor.m

@@ -119,7 +119,9 @@ typedef void (^WSMessageCallback)(NSError *error, NSDictionary *reply);
 
   [_jsQueue addOperationWithBlock:^{
     if (!self.valid) {
-      NSError *error = [NSError errorWithDomain:@"WS" code:1 userInfo:@{NSLocalizedDescriptionKey:@"socket closed"}];
+      NSError *error = [NSError errorWithDomain:@"WS" code:1 userInfo:@{
+        NSLocalizedDescriptionKey: @"socket closed"
+      }];
       callback(error, nil);
       return;
     }

React/Base/RCTBridge.h

@@ -28,6 +28,11 @@ typedef NSArray *(^RCTBridgeModuleProviderBlock)(void);
 
 extern NSString *const RCTReloadBridge;
 
+/**
+ * This function returns the module name for a given class.
+ */
+extern NSString *RCTBridgeModuleNameForClass(Class bridgeModuleClass);
+
 /**
  * Async batched bridge used to communicate with the JavaScript application.
  */
@@ -81,14 +86,6 @@ extern NSString *const RCTReloadBridge;
  */
 @property (nonatomic, readonly) dispatch_queue_t shadowQueue;
 
-/**
- * Global logging function that will print to both xcode and JS debugger consoles.
- *
- * NOTE: Use via RCTLog* macros defined in RCTLog.h
- * TODO (#5906496): should log function be exposed here, or could it be a module?
- */
-+ (void)log:(NSArray *)objects level:(NSString *)level;
-
 @property (nonatomic, copy, readonly) NSDictionary *launchOptions;
 
 

React/Base/RCTBridge.m

@@ -22,6 +22,7 @@
 #import "RCTJavaScriptLoader.h"
 #import "RCTKeyCommands.h"
 #import "RCTLog.h"
+#import "RCTRedBox.h"
 #import "RCTRootView.h"
 #import "RCTSparseArray.h"
 #import "RCTUtils.h"
@@ -41,10 +42,7 @@ typedef NS_ENUM(NSUInteger, RCTBridgeFields) {
 
 NSString *const RCTReloadBridge = @"RCTReloadBridge";
 
-/**
+NSString *RCTBridgeModuleNameForClass(Class cls)
- * This function returns the module name for a given class.
- */
-static NSString *RCTModuleNameForClass(Class cls)
 {
   return [cls respondsToSelector:@selector(moduleName)] ? [cls moduleName] : NSStringFromClass(cls);
 }
@@ -92,7 +90,7 @@ static NSArray *RCTBridgeModuleClassesByModuleID(void)
         [(NSMutableArray *)modules addObject:cls];
 
         // Add module name
-        NSString *moduleName = RCTModuleNameForClass(cls);
+        NSString *moduleName = RCTBridgeModuleNameForClass(cls);
         [(NSMutableArray *)RCTModuleNamesByID addObject:moduleName];
       }
     });
@@ -187,7 +185,7 @@ static Class _globalExecutorClass;
           RCT_ARG_BLOCK( \
             if (json && ![json isKindOfClass:[_class class]]) { \
               RCTLogError(@"Argument %tu (%@) of %@.%@ should be of type %@", index, \
-                json, RCTModuleNameForClass(_moduleClass), _JSMethodName, [_class class]); \
+                json, RCTBridgeModuleNameForClass(_moduleClass), _JSMethodName, [_class class]); \
               return; \
             } \
             _logic \
@@ -203,7 +201,7 @@ static Class _globalExecutorClass;
           RCT_ARG_BLOCK( \
             if (json && ![json respondsToSelector:@selector(_selector)]) { \
               RCTLogError(@"Argument %tu (%@) of %@.%@ does not respond to selector: %@", \
-                index, json, RCTModuleNameForClass(_moduleClass), _JSMethodName, @#_selector); \
+                index, json, RCTBridgeModuleNameForClass(_moduleClass), _JSMethodName, @#_selector); \
               return; \
             } \
             _type value = [json _selector];                     \
@@ -231,7 +229,7 @@ static Class _globalExecutorClass;
             RCT_ARG_BLOCK(
               if (json && ![json isKindOfClass:[NSNumber class]]) {
                 RCTLogError(@"Argument %tu (%@) of %@.%@ should be a number", index,
-                            json, RCTModuleNameForClass(_moduleClass), _JSMethodName);
+                            json, RCTBridgeModuleNameForClass(_moduleClass), _JSMethodName);
                 return;
               }
               // Marked as autoreleasing, because NSInvocation doesn't retain arguments
@@ -268,7 +266,7 @@ static Class _globalExecutorClass;
   // Safety check
   if (arguments.count != _argumentBlocks.count) {
     RCTLogError(@"%@.%@ was called with %zd arguments, but expects %zd",
-                RCTModuleNameForClass(_moduleClass), _JSMethodName,
+                RCTBridgeModuleNameForClass(_moduleClass), _JSMethodName,
                 arguments.count, _argumentBlocks.count);
     return;
   }
@@ -544,7 +542,7 @@ static id<RCTJavaScriptExecutor> _latestJSExecutor;
   // Register passed-in module instances
   NSMutableDictionary *preregisteredModules = [[NSMutableDictionary alloc] init];
   for (id<RCTBridgeModule> module in _moduleProvider ? _moduleProvider() : nil) {
-    preregisteredModules[RCTModuleNameForClass([module class])] = module;
+    preregisteredModules[RCTBridgeModuleNameForClass([module class])] = module;
   }
 
   // Instantiate modules
@@ -895,27 +893,18 @@ static id<RCTJavaScriptExecutor> _latestJSExecutor;
   return (_latestJSExecutor != nil && [_latestJSExecutor isValid]);
 }
 
-+ (void)log:(NSArray *)objects level:(NSString *)level
++ (void)logMessage:(NSString *)message level:(NSString *)level
 {
   if (!_latestJSExecutor || ![_latestJSExecutor isValid]) {
-    RCTLogError(@"ERROR: No valid JS executor to log %@.", objects);
+    RCTLogError(@"ERROR: No valid JS executor to log '%@'.", message);
     return;
   }
-  NSMutableArray *args = [NSMutableArray arrayWithObject:level];
 
-  // TODO (#5906496): Find out and document why we skip the first object
+  // Note: the js executor could get invalidated while we're trying to call
-  for (id ob in [objects subarrayWithRange:(NSRange){1, [objects count] - 1}]) {
+  // this...need to watch out for that.
-    if ([NSJSONSerialization isValidJSONObject:@[ob]]) {
-      [args addObject:ob];
-    } else {
-      [args addObject:[ob description]];
-    }
-  }
-
-  // Note: the js executor could get invalidated while we're trying to call this...need to watch out for that.
   [_latestJSExecutor executeJSCall:@"RCTLog"
                             method:@"logIfNoNativeHook"
-                         arguments:args
+                         arguments:@[level, message]
                           callback:^(id json, NSError *error) {}];
 }
 

React/Base/RCTConvert.h

@@ -145,7 +145,7 @@ RCT_CUSTOM_CONVERTER(type, name, [json getter])
   }                                            \
   @catch (__unused NSException *e) {           \
     RCTLogError(@"JSON value '%@' of type '%@' cannot be converted to '%s'", \
-    json, [json class], #type); \
+    json, [json classForCoder], #type); \
     json = nil; \
     return code; \
   } \
@@ -181,7 +181,8 @@ RCT_CUSTOM_CONVERTER(type, type, [[self NSNumber:json] getter])
     return default;                                       \
   }                                                       \
   if (![json isKindOfClass:[NSString class]]) {           \
-    RCTLogError(@"Expected NSNumber or NSString for %s, received %@: %@", #type, [json class], json); \
+    RCTLogError(@"Expected NSNumber or NSString for %s, received %@: %@", \
+                #type, [json classForCoder], json);       \
   }                                                       \
   id value = mapping[json];                               \
   if(!value && [json description].length > 0) {           \

React/Base/RCTConvert.m

@@ -45,7 +45,7 @@ RCT_CONVERTER(NSString *, NSString, description)
     }
     return number;
   } else if (json && json != [NSNull null]) {
-    RCTLogError(@"JSON value '%@' of class %@ could not be interpreted as a number", json, [json class]);
+    RCTLogError(@"JSON value '%@' of class %@ could not be interpreted as a number", json, [json classForCoder]);
   }
   return nil;
 }
@@ -53,7 +53,7 @@ RCT_CONVERTER(NSString *, NSString, description)
 + (NSURL *)NSURL:(id)json
 {
   if (![json isKindOfClass:[NSString class]]) {
-    RCTLogError(@"Expected NSString for NSURL, received %@: %@", [json class], json);
+    RCTLogError(@"Expected NSString for NSURL, received %@: %@", [json classForCoder], json);
     return nil;
   }
 
@@ -98,7 +98,7 @@ RCT_CONVERTER(NSString *, NSString, description)
     }
     return date;
   } else if (json && json != [NSNull null]) {
-    RCTLogError(@"JSON value '%@' of class %@ could not be interpreted as a date", json, [json class]);
+    RCTLogError(@"JSON value '%@' of class %@ could not be interpreted as a date", json, [json classForCoder]);
   }
   return nil;
 }
@@ -234,7 +234,8 @@ RCT_ENUM_CONVERTER(UIBarStyle, (@{
         ((CGFloat *)&result)[i] = [self CGFloat:json[fields[i]]]; \
       }                                                  \
     } else if (json && json != [NSNull null]) {          \
-      RCTLogError(@"Expected NSArray or NSDictionary for %s, received %@: %@", #type, [json class], json); \
+      RCTLogError(@"Expected NSArray or NSDictionary for %s, received %@: %@", \
+                  #type, [json classForCoder], json);    \
     }                                                    \
     return result;                                       \
   }                                                      \
@@ -511,8 +512,8 @@ RCT_CGSTRUCT_CONVERTER(CGAffineTransform, (@[
 
   } else if (json && ![json isKindOfClass:[NSNull class]]) {
 
-    RCTLogError(@"Expected NSArray, NSDictionary or NSString for UIColor, \
+    RCTLogError(@"Expected NSArray, NSDictionary or NSString for UIColor, received %@: %@",
-                received %@: %@", [json class], json);
+                [json classForCoder], json);
   }
 
   // Default color
@@ -538,7 +539,7 @@ RCT_CGSTRUCT_CONVERTER(CGAffineTransform, (@[
   // image itself) so as to reduce overhead on subsequent checks of the same input
 
   if (![json isKindOfClass:[NSString class]]) {
-    RCTLogError(@"Expected NSString for UIImage, received %@: %@", [json class], json);
+    RCTLogError(@"Expected NSString for UIImage, received %@: %@", [json classForCoder], json);
     return nil;
   }
 

React/Base/RCTLog.h

@@ -7,58 +7,138 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  */
 
+#import <Foundation/Foundation.h>
+
 #import "RCTAssert.h"
-#import "RCTRedBox.h"
-
-#define RCTLOG_INFO 1
-#define RCTLOG_WARN 2
-#define RCTLOG_ERROR 3
-#define RCTLOG_MUSTFIX 4
-
-// If set to e.g. `RCTLOG_ERROR`, will assert after logging the first error.
-#if DEBUG
-#define RCTLOG_FATAL_LEVEL RCTLOG_MUSTFIX
-#define RCTLOG_REDBOX_LEVEL RCTLOG_ERROR
-#else
-#define RCTLOG_FATAL_LEVEL (RCTLOG_MUSTFIX + 1)
-#define RCTLOG_REDBOX_LEVEL (RCTLOG_MUSTFIX + 1)
-#endif
-
-// If defined, only log messages that match this regex will fatal
-#define RCTLOG_FATAL_REGEX nil
-
-extern __unsafe_unretained NSString *RCTLogLevels[];
-
-#define _RCTLog(_level, ...) do {                                                                                                          \
-  NSString *__RCTLog__levelStr = RCTLogLevels[_level - 1];                                                                                 \
-  NSString *__RCTLog__msg = RCTLogObjects(RCTLogFormat(__FILE__, __LINE__, __PRETTY_FUNCTION__, __VA_ARGS__), __RCTLog__levelStr);         \
-  if (_level >= RCTLOG_FATAL_LEVEL) {                                                                                                      \
-    BOOL __RCTLog__fail = YES;                                                                                                             \
-    if (RCTLOG_FATAL_REGEX) {                                                                                                              \
-      NSRegularExpression *__RCTLog__regex = [NSRegularExpression regularExpressionWithPattern:RCTLOG_FATAL_REGEX options:0 error:NULL];   \
-      __RCTLog__fail = [__RCTLog__regex numberOfMatchesInString:__RCTLog__msg options:0 range:NSMakeRange(0, [__RCTLog__msg length])] > 0; \
-    }                                                                                                                                      \
-    RCTCAssert(!__RCTLog__fail, @"RCTLOG_FATAL_LEVEL %@: %@", __RCTLog__levelStr, __RCTLog__msg);                                          \
-  }                                                                                                                                        \
-  if (_level >= RCTLOG_REDBOX_LEVEL) {                                                                                                     \
-    [[RCTRedBox sharedInstance] showErrorMessage:__RCTLog__msg];                                                                           \
-  }                                                                                                                                        \
-} while (0)
-
-#define RCTLog(...) _RCTLog(RCTLOG_INFO, __VA_ARGS__)
-#define RCTLogInfo(...) _RCTLog(RCTLOG_INFO, __VA_ARGS__)
-#define RCTLogWarn(...) _RCTLog(RCTLOG_WARN, __VA_ARGS__)
-#define RCTLogError(...) _RCTLog(RCTLOG_ERROR, __VA_ARGS__)
-#define RCTLogMustFix(...) _RCTLog(RCTLOG_MUSTFIX, __VA_ARGS__)
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-NSString *RCTLogObjects(NSArray *objects, NSString *level);
+/**
-NSArray *RCTLogFormat(const char *file, int lineNumber, const char *funcName, NSString *format, ...) NS_FORMAT_FUNCTION(4,5);
+ * Thresholds for logs to raise an assertion, or display redbox, respectively.
+ * You can override these values when debugging in order to tweak the default
+ * logging behavior.
+ */
+#define RCTLOG_FATAL_LEVEL RCTLogLevelMustFix
+#define RCTLOG_REDBOX_LEVEL RCTLogLevelError
 
-void RCTInjectLogFunction(void (^logFunction)(NSString *msg));
+/**
+ * A regular expression that can be used to selectively limit the throwing of
+ * a exception to specific log contents.
+ */
+#define RCTLOG_FATAL_REGEX nil
+
+/**
+ * An enum representing the severity of the log message.
+ */
+typedef NS_ENUM(NSInteger, RCTLogLevel) {
+  RCTLogLevelInfo = 1,
+  RCTLogLevelWarning = 2,
+  RCTLogLevelError = 3,
+  RCTLogLevelMustFix = 4
+};
+
+/**
+ * A block signature to be used for custom logging functions. In most cases you
+ * will want to pass these arguments to the RCTFormatLog function in order to
+ * generate a string, or use the RCTSimpleLogFunction() constructor to register
+ * a simple function that does not use all of the arguments.
+ */
+typedef void (^RCTLogFunction)(
+  RCTLogLevel level,
+  NSString *fileName,
+  NSNumber *lineNumber,
+  NSString *message
+);
+
+/**
+ * A method to generate a string from a collection of log data. To omit any
+ * particular data from the log, just pass nil or zero for the argument.
+ */
+NSString *RCTFormatLog(
+  NSDate *timestamp,
+  NSThread *thread,
+  RCTLogLevel level,
+  NSString *fileName,
+  NSNumber *lineNumber,
+  NSString *message
+);
+
+/**
+ * A method to generate a log function from a block with a much simpler
+ * template. The message passed to the simpler block is equivalent to the
+ * output of the RCTFormatLog() function.
+ */
+RCTLogFunction RCTSimpleLogFunction(void (^logFunction)(RCTLogLevel level, NSString *message));
+
+/**
+ * The default logging function used by RCTLogXX.
+ */
+extern RCTLogFunction RCTDefaultLogFunction;
+
+/**
+ * These methods get and set the current logging threshold. This is the level
+ * below which logs will be ignored. Default is RCTLogLevelInfo for debug and
+ * RCTLogLevelError for production.
+ */
+void RCTSetLogThreshold(RCTLogLevel threshold);
+RCTLogLevel RCTGetLogThreshold(void);
+
+/**
+ * These methods get and set the current logging function called by the RCTLogXX
+ * macros. You can use these to replace the standard behavior with custom log
+ * functionality.
+ */
+void RCTSetLogFunction(RCTLogFunction logFunction);
+RCTLogFunction RCTGetLogFunction(void);
+
+/**
+ * This appends additional code to the existing log function, without replacing
+ * the existing functionality. Useful if you just want to forward logs to an
+ * extra service without changing the default behavior.
+ */
+void RCTAddLogFunction(RCTLogFunction logFunction);
+
+/**
+ * This method adds a conditional prefix to any messages logged within the scope
+ * of the passed block. This is useful for adding additional context to log
+ * messages. The block will be performed synchronously on the current thread.
+ */
+void RCTPerformBlockWithLogPrefix(void (^block)(void), NSString *prefix);
+
+/**
+ * Private logging functions - ignore these.
+ */
+void _RCTLogFormat(RCTLogLevel, const char *, int, NSString *, ...) NS_FORMAT_FUNCTION(4,5);
+#define _RCTLog(lvl, ...) do { \
+  NSString *msg = [NSString stringWithFormat:__VA_ARGS__]; \
+  if (lvl >= RCTLOG_FATAL_LEVEL) { \
+    BOOL fail = YES; \
+    if (RCTLOG_FATAL_REGEX) { \
+      if ([msg rangeOfString:RCTLOG_FATAL_REGEX options:NSRegularExpressionSearch].length) { \
+        fail = NO; \
+      } \
+    } \
+    RCTCAssert(!fail, @"FATAL ERROR: %@", msg); \
+  }\
+  _RCTLogFormat(lvl, __FILE__, __LINE__, __VA_ARGS__); \
+} while (0)
+
+/**
+ * Legacy injection function - don't use this.
+ */
+void RCTInjectLogFunction(void (^)(NSString *msg));
+
+/**
+ * Logging macros. Use these to log information, warnings and errors in your
+ * own code.
+ */
+#define RCTLog(...) _RCTLog(RCTLogLevelInfo, __VA_ARGS__)
+#define RCTLogInfo(...) _RCTLog(RCTLogLevelInfo, __VA_ARGS__)
+#define RCTLogWarn(...) _RCTLog(RCTLogLevelWarning, __VA_ARGS__)
+#define RCTLogError(...) _RCTLog(RCTLogLevelError, __VA_ARGS__)
+#define RCTLogMustFix(...) _RCTLog(RCTLogLevelMustFix, __VA_ARGS__)
 
 #ifdef __cplusplus
 }

React/Base/RCTLog.m

@@ -9,85 +9,218 @@
 
 #import "RCTLog.h"
 
+#import "RCTAssert.h"
 #import "RCTBridge.h"
+#import "RCTRedBox.h"
 
-__unsafe_unretained NSString *RCTLogLevels[] = {
+@interface RCTBridge (Logging)
-  @"info",
+
-  @"warn",
++ (void)logMessage:(NSString *)message level:(NSString *)level;
-  @"error",
+
-  @"mustfix"
+@end
+
+static NSString *const RCTLogPrefixStack = @"RCTLogPrefixStack";
+
+const char *RCTLogLevels[] = {
+  "info",
+  "warn",
+  "error",
+  "mustfix"
 };
 
-static void (^RCTInjectedLogFunction)(NSString *msg);
+static RCTLogFunction RCTCurrentLogFunction;
+static RCTLogLevel RCTCurrentLogThreshold;
 
-void RCTInjectLogFunction(void (^logFunction)(NSString *msg)) {
+void RCTLogSetup(void) __attribute__((constructor));
-  RCTInjectedLogFunction = logFunction;
+void RCTLogSetup()
-}
-
-static inline NSString *_RCTLogPreamble(const char *file, int lineNumber, const char *funcName)
 {
-  NSString *threadName = [[NSThread currentThread] name];
+  RCTCurrentLogFunction = RCTDefaultLogFunction;
-  NSString *fileName=[[NSString stringWithUTF8String:file] lastPathComponent];
-  if (!threadName || threadName.length <= 0) {
-    threadName = [NSString stringWithFormat:@"%p", [NSThread currentThread]];
-  }
-  return [NSString stringWithFormat:@"[RCTLog][tid:%@][%@:%d]>", threadName, fileName, lineNumber];
-}
 
-// TODO (#5906496): Does this need to be tied to RCTBridge?
+#if DEBUG
-NSString *RCTLogObjects(NSArray *objects, NSString *level)
+  RCTCurrentLogThreshold = RCTLogLevelInfo - 1;
-{
+#else
-  NSString *str = objects[0];
+  RCTCurrentLogThreshold = RCTLogLevelError;
-#if TARGET_IPHONE_SIMULATOR
-  if ([RCTBridge hasValidJSExecutor]) {
-    fprintf(stderr, "%s\n", [str UTF8String]); // don't print timestamps and other junk
-    [RCTBridge log:objects level:level];
-  } else
 #endif
-  {
+
-    // Print normal errors with timestamps when not in simulator.
-    // Non errors are already compiled out above, so log as error here.
-    if (RCTInjectedLogFunction) {
-      RCTInjectedLogFunction(str);
-    } else {
-      NSLog(@">\n  %@", str);
-    }
-  }
-  return str;
 }
 
-// Returns array of objects.  First arg is a simple string to print, remaining args
+RCTLogFunction RCTDefaultLogFunction = ^(
-// are objects to pass through to the debugger so they are inspectable in the console.
+  RCTLogLevel level,
-NSArray *RCTLogFormat(const char *file, int lineNumber, const char *funcName, NSString *format, ...)
+  NSString *fileName,
+  NSNumber *lineNumber,
+  NSString *message
+)
 {
+  NSString *log = RCTFormatLog(
+    [NSDate date], [NSThread currentThread], level, fileName, lineNumber, message
+  );
+  fprintf(stderr, "%s\n", log.UTF8String);
+};
+
+void RCTSetLogFunction(RCTLogFunction logFunction)
+{
+  RCTCurrentLogFunction = logFunction;
+}
+
+RCTLogFunction RCTGetLogFunction()
+{
+  return RCTCurrentLogFunction;
+}
+
+void RCTAddLogFunction(RCTLogFunction logFunction)
+{
+  RCTLogFunction existing = RCTCurrentLogFunction;
+  if (existing) {
+    RCTCurrentLogFunction = ^(RCTLogLevel level,
+                              NSString *fileName,
+                              NSNumber *lineNumber,
+                              NSString *message) {
+
+      existing(level, fileName, lineNumber, message);
+      logFunction(level, fileName, lineNumber, message);
+    };
+  } else {
+    RCTCurrentLogFunction = logFunction;
+  }
+}
+
+void RCTPerformBlockWithLogPrefix(void (^block)(void), NSString *prefix)
+{
+  NSMutableDictionary *threadDictionary = [NSThread currentThread].threadDictionary;
+  NSMutableArray *prefixStack = threadDictionary[RCTLogPrefixStack];
+  if (!prefixStack) {
+    prefixStack = [[NSMutableArray alloc] init];
+    threadDictionary[RCTLogPrefixStack] = prefixStack;
+  }
+  [prefixStack addObject:prefix];
+  block();
+  [prefixStack removeLastObject];
+}
+
+NSString *RCTFormatLog(
+  NSDate *timestamp,
+  NSThread *thread,
+  RCTLogLevel level,
+  NSString *fileName,
+  NSNumber *lineNumber,
+  NSString *message
+)
+{
+  NSMutableString *log = [[NSMutableString alloc] init];
+  if (timestamp) {
+    static NSDateFormatter *formatter;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+      formatter = [[NSDateFormatter alloc] init];
+      formatter.dateFormat = formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss.SSS ";
+    });
+    [log appendString:[formatter stringFromDate:timestamp]];
+  }
+  [log appendString:@"[react]"];
+  if (level) {
+    [log appendFormat:@"[%s]", RCTLogLevels[level - 1]];
+  }
+  if (thread) {
+    NSString *threadName = thread.name;
+    if (threadName.length == 0) {
+#if DEBUG
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+      threadName = @(dispatch_queue_get_label(dispatch_get_current_queue()));
+#pragma clang diagnostic pop
+#else
+      threadName = [NSString stringWithFormat:@"%p", thread];
+#endif
+    }
+    [log appendFormat:@"[tid:%@]", threadName];
+  }
+  if (fileName) {
+    fileName = [fileName lastPathComponent];
+    if (lineNumber) {
+      [log appendFormat:@"[%@:%@]", fileName, lineNumber];
+    } else {
+      [log appendFormat:@"[%@]", fileName];
+    }
+  }
+  if (message) {
+    [log appendString:@" "];
+    [log appendString:message];
+  }
+  return log;
+}
+
+RCTLogFunction RCTSimpleLogFunction(void (^logFunction)(RCTLogLevel level, NSString *message))
+{
+  return ^(RCTLogLevel level,
+           NSString *fileName,
+           NSNumber *lineNumber,
+           NSString *message) {
+
+    logFunction(level, RCTFormatLog(
+      [NSDate date], [NSThread currentThread], level, fileName, lineNumber, message
+    ));
+  };
+}
+
+void _RCTLogFormat(RCTLogLevel level, const char *fileName, int lineNumber, NSString *format, ...)
+{
+  if (RCTCurrentLogFunction && level >= RCTCurrentLogThreshold) {
+
+    // Get message
     va_list args;
     va_start(args, format);
-  NSString *preamble = _RCTLogPreamble(file, lineNumber, funcName);
+    __block NSString *message = [[NSString alloc] initWithFormat:format arguments:args];
+    va_end(args);
+
+    // Add prefix
+    NSMutableDictionary *threadDictionary = [NSThread currentThread].threadDictionary;
+    NSArray *prefixStack = threadDictionary[RCTLogPrefixStack];
+    NSString *prefix = [prefixStack lastObject];
+    if (prefix) {
+      message = [prefix stringByAppendingString:message];
+    }
+
+    // Call log function
+    RCTCurrentLogFunction(
+      level, fileName ? @(fileName) : nil, (lineNumber >= 0) ? @(lineNumber) : nil, message
+    );
+
+#if DEBUG
+
+    // Log to red box
+    if (level >= RCTLOG_REDBOX_LEVEL) {
+      [[RCTRedBox sharedInstance] showErrorMessage:message];
+    }
+
+    // Log to JS executor
+    if ([RCTBridge hasValidJSExecutor]) {
+      [RCTBridge logMessage:message level:level ? @(RCTLogLevels[level - 1]) : @"info"];
+    }
+
+#endif
 
-  // Pull out NSObjects so we can pass them through as inspectable objects to the js debugger
-  NSArray *formatParts = [format componentsSeparatedByString:@"%"];
-  NSMutableArray *objects = [NSMutableArray arrayWithObject:preamble];
-  BOOL valid = YES;
-  for (int i = 0; i < formatParts.count; i++) {
-    if (i == 0) { // first part is always a string
-      [objects addObject:formatParts[i]];
-    } else {
-      if (valid && [formatParts[i] length] && [formatParts[i] characterAtIndex:0] == '@') {
-        id obj = va_arg(args, id);
-        [objects addObject:obj ?: @"null"];
-        [objects addObject:[formatParts[i] substringFromIndex:1]]; // remove formatting char
-      } else {
-        // We could determine the type (double, int?) of the va_arg by parsing the formatPart, but for now we just bail.
-        valid = NO;
-        [objects addObject:[NSString stringWithFormat:@"unknown object for %%%@", formatParts[i]]];
   }
 }
+
+#pragma mark - Deprecated
+
+void RCTInjectLogFunction(void (^logFunction)(NSString *msg))
+{
+  RCTSetLogFunction(^(RCTLogLevel level,
+                      NSString *fileName,
+                      NSNumber *lineNumber,
+                      NSString *message) {
+
+    if (level > RCTLogLevelError) {
+
+      // Use custom log function
+      NSString *loc = fileName ? [NSString stringWithFormat:@"[%@:%@] ", fileName, lineNumber] : @"";
+      logFunction([loc stringByAppendingString:message]);
+
+    } else if (RCTDefaultLogFunction && level >= RCTCurrentLogThreshold) {
+
+      // Use default logger
+      RCTDefaultLogFunction(level, fileName, lineNumber, message);
     }
-  va_end(args);
+  });
-  va_start(args, format);
-  NSString *strOut = [preamble stringByAppendingString:[[NSString alloc] initWithFormat:format arguments:args]];
-  va_end(args);
-  NSMutableArray *objectsOut = [NSMutableArray arrayWithObject:strOut];
-  [objectsOut addObjectsFromArray:objects];
-  return objectsOut;
 }

React/Base/RCTRootView.h

@@ -17,6 +17,9 @@ extern NSString *const RCTReloadViewsNotification;
 
 @interface RCTRootView : UIView <RCTInvalidating>
 
+/**
+ * - Designated initializer -
+ */
 - (instancetype)initWithBridge:(RCTBridge *)bridge
                     moduleName:(NSString *)moduleName NS_DESIGNATED_INITIALIZER;
 
@@ -39,6 +42,10 @@ extern NSString *const RCTReloadViewsNotification;
  */
 @property (nonatomic, copy, readonly) NSString *moduleName;
 
+/**
+ * The bridge used by the root view. Bridges can be shared between multiple
+ * root views, so you can use this property to initialize another RCTRootView.
+ */
 @property (nonatomic, strong, readonly) RCTBridge *bridge;
 
 /**

React/Base/RCTRootView.m

@@ -17,7 +17,6 @@
 #import "RCTEventDispatcher.h"
 #import "RCTKeyCommands.h"
 #import "RCTLog.h"
-#import "RCTRedBox.h"
 #import "RCTSourceCode.h"
 #import "RCTTouchHandler.h"
 #import "RCTUIManager.h"

React/Executors/RCTContextExecutor.m

@@ -38,23 +38,18 @@ static JSValueRef RCTNativeLoggingHook(JSContextRef context, JSObjectRef object,
     if (!string) {
       return JSValueMakeUndefined(context);
     }
-
+    NSString *message = (__bridge_transfer NSString *)JSStringCopyCFString(kCFAllocatorDefault, string);
-    NSString *str = (__bridge_transfer NSString *)JSStringCopyCFString(kCFAllocatorDefault, string);
+    JSStringRelease(string);
-    NSError *error = nil;
     NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:
                                   @"( stack: )?([_a-z0-9]*)@?(http://|file:///)[a-z.0-9:/_-]+/([a-z0-9_]+).includeRequire.runModule.bundle(:[0-9]+:[0-9]+)"
                                                                            options:NSRegularExpressionCaseInsensitive
-                                                                             error:&error];
+                                                                             error:NULL];
-    NSString *modifiedString = [regex stringByReplacingMatchesInString:str options:0 range:NSMakeRange(0, [str length]) withTemplate:@"[$4$5]  \t$2"];
+    message = [regex stringByReplacingMatchesInString:message
+                                              options:0
+                                                range:(NSRange){0, message.length}
+                                         withTemplate:@"[$4$5]  \t$2"];
 
-    modifiedString = [@"RCTJSLog> " stringByAppendingString:modifiedString];
+    _RCTLogFormat(0, NULL, -1, @"%@", message);
-#if TARGET_IPHONE_SIMULATOR
-    fprintf(stderr, "%s\n", [modifiedString UTF8String]); // don't print timestamps and other junk
-#else
-    // Print normal errors with timestamps to files when not in simulator.
-    RCTLogObjects(@[modifiedString], @"log");
-#endif
-    JSStringRelease(string);
   }
 
   return JSValueMakeUndefined(context);

React/Modules/RCTAlertManager.m

@@ -9,6 +9,7 @@
 
 #import "RCTAlertManager.h"
 
+#import "RCTAssert.h"
 #import "RCTLog.h"
 
 @interface RCTAlertManager() <UIAlertViewDelegate>

React/Modules/RCTUIManager.m

@@ -197,6 +197,11 @@ static UIViewAnimationCurve UIViewAnimationCurveFromRCTAnimationType(RCTAnimatio
 
 @synthesize bridge = _bridge;
 
+/**
+ * Declared in RCTBridge.
+ */
+extern NSString *RCTBridgeModuleNameForClass(Class cls);
+
 /**
  * This function derives the view name automatically
  * from the module name.
@@ -334,7 +339,7 @@ static NSString *RCTViewNameForModuleName(NSString *moduleName)
 
   dispatch_async(_bridge.shadowQueue, ^{
     RCTShadowView *rootShadowView = _shadowViewRegistry[reactTag];
-    RCTAssert(rootShadowView != nil, @"Could not locate root view with tag %@", reactTag);
+    RCTAssert(rootShadowView != nil, @"Could not locate root view with tag #%@", reactTag);
     rootShadowView.frame = frame;
     [rootShadowView updateLayout];
 
@@ -672,7 +677,7 @@ static NSString *RCTViewNameForModuleName(NSString *moduleName)
   }
 }
 
-static BOOL RCTCallPropertySetter(SEL setter, id value, id view, id defaultView, RCTViewManager *manager)
+static BOOL RCTCallPropertySetter(NSString *key, SEL setter, id value, id view, id defaultView, RCTViewManager *manager)
 {
   // TODO: cache respondsToSelector tests
   if ([manager respondsToSelector:setter]) {
@@ -681,7 +686,25 @@ static BOOL RCTCallPropertySetter(SEL setter, id value, id view, id defaultView,
       value = nil;
     }
 
+    void (^block)() = ^{
       ((void (*)(id, SEL, id, id, id))objc_msgSend)(manager, setter, value, view, defaultView);
+    };
+
+#if DEBUG
+
+    NSString *viewName = RCTViewNameForModuleName(RCTBridgeModuleNameForClass([manager class]));
+    NSString *logPrefix = [NSString stringWithFormat:
+                           @"Error setting property '%@' of %@ with tag #%@: ",
+                           key, viewName, [view reactTag]];
+
+    RCTPerformBlockWithLogPrefix(block, logPrefix);
+
+#else
+
+    block();
+
+#endif
+
     return YES;
   }
   return NO;
@@ -693,7 +716,7 @@ static void RCTSetViewProps(NSDictionary *props, UIView *view,
   [props enumerateKeysAndObjectsUsingBlock:^(NSString *key, id obj, BOOL *stop) {
 
     SEL setter = NSSelectorFromString([NSString stringWithFormat:@"set_%@:forView:withDefaultView:", key]);
-    RCTCallPropertySetter(setter, obj, view, defaultView, manager);
+    RCTCallPropertySetter(key, setter, obj, view, defaultView, manager);
 
   }];
 }
@@ -704,7 +727,7 @@ static void RCTSetShadowViewProps(NSDictionary *props, RCTShadowView *shadowView
   [props enumerateKeysAndObjectsUsingBlock:^(NSString *key, id obj, BOOL *stop) {
 
     SEL setter = NSSelectorFromString([NSString stringWithFormat:@"set_%@:forShadowView:withDefaultView:", key]);
-    RCTCallPropertySetter(setter, obj, shadowView, defaultView, manager);
+    RCTCallPropertySetter(key, setter, obj, shadowView, defaultView, manager);
 
   }];
 
@@ -875,7 +898,7 @@ static void RCTSetShadowViewProps(NSDictionary *props, RCTShadowView *shadowView
   [self addUIBlock:^(RCTUIManager *uiManager, RCTSparseArray *viewRegistry) {
     UIView *view = viewRegistry[reactTag];
     if (!view) {
-      RCTLogError(@"measure cannot find view with tag %@", reactTag);
+      RCTLogError(@"measure cannot find view with tag #%@", reactTag);
       return;
     }
     CGRect frame = view.frame;
@@ -1039,7 +1062,7 @@ static void RCTMeasureLayout(RCTShadowView *view,
         uiManager.mainScrollView = (id<RCTScrollableProtocol>)rkObject;
         ((id<RCTScrollableProtocol>)rkObject).nativeMainScrollDelegate = uiManager.nativeMainScrollDelegate;
       } else {
-        RCTCAssert(NO, @"Tag %@ does not conform to RCTScrollableProtocol", reactTag);
+        RCTCAssert(NO, @"Tag #%@ does not conform to RCTScrollableProtocol", reactTag);
       }
     } else {
       uiManager.mainScrollView = nil;
@@ -1056,7 +1079,7 @@ static void RCTMeasureLayout(RCTShadowView *view,
     if ([view conformsToProtocol:@protocol(RCTScrollableProtocol)]) {
       [(id<RCTScrollableProtocol>)view scrollToOffset:CGPointMake([offsetX floatValue], [offsetY floatValue]) animated:YES];
     } else {
-      RCTLogError(@"tried to scrollToOffset: on non-RCTScrollableProtocol view %@ with tag %@", view, reactTag);
+      RCTLogError(@"tried to scrollToOffset: on non-RCTScrollableProtocol view %@ with tag #%@", view, reactTag);
     }
   }];
 }
@@ -1070,7 +1093,7 @@ static void RCTMeasureLayout(RCTShadowView *view,
         if ([view conformsToProtocol:@protocol(RCTScrollableProtocol)]) {
             [(id<RCTScrollableProtocol>)view scrollToOffset:CGPointMake([offsetX floatValue], [offsetY floatValue]) animated:NO];
         } else {
-            RCTLogError(@"tried to scrollToOffset: on non-RCTScrollableProtocol view %@ with tag %@", view, reactTag);
+            RCTLogError(@"tried to scrollToOffset: on non-RCTScrollableProtocol view %@ with tag #%@", view, reactTag);
         }
     }];
 }
@@ -1084,7 +1107,7 @@ static void RCTMeasureLayout(RCTShadowView *view,
     if ([view conformsToProtocol:@protocol(RCTScrollableProtocol)]) {
       [(id<RCTScrollableProtocol>)view zoomToRect:[RCTConvert CGRect:rectDict] animated:YES];
     } else {
-      RCTLogError(@"tried to zoomToRect: on non-RCTScrollableProtocol view %@ with tag %@", view, reactTag);
+      RCTLogError(@"tried to zoomToRect: on non-RCTScrollableProtocol view %@ with tag #%@", view, reactTag);
     }
   }];
 }

React/Views/RCTScrollViewManager.m

@@ -72,7 +72,7 @@ RCT_DEPRECATED_VIEW_PROPERTY(throttleScrollCallbackMS, scrollEventThrottle)
 
     UIView *view = viewRegistry[reactTag];
     if (!view) {
-      RCTLogError(@"Cannot find view with tag %@", reactTag);
+      RCTLogError(@"Cannot find view with tag #%@", reactTag);
       return;
     }