Implement lazy discovery scaffolding for loading NativeModules on demand.

Reviewed By: javache

Differential Revision: D5364734

fbshipit-source-id: 5162f7d41434a3ba38c82fa610e84f865bfacf50

Author: Dmitry Zakharov

React/Base/RCTBridge+Private.h

@@ -114,6 +114,11 @@ RCT_EXTERN void RCTVerifyAllModulesExported(NSArray *extraModules);
  */
 - (RCTModuleData *)moduleDataForName:(NSString *)moduleName;
 
+/**
+* Registers additional classes with the ModuleRegistry.
+*/
+- (void)registerAdditionalModuleClasses:(NSArray<Class> *)newModules;
+
 /**
  * Systrace profiler toggling methods exposed for the RCTDevMenu
  */

React/Base/RCTBridge.m

@@ -353,6 +353,11 @@ - (void)invalidate
   }
 }
 
+- (void)registerAdditionalModuleClasses:(NSArray<Class> *)modules
+{
+  [self.batchedBridge registerAdditionalModuleClasses:modules];
+}
+
 - (void)enqueueJSCall:(NSString *)moduleDotMethod args:(NSArray *)args
 {
   NSArray<NSString *> *ids = [moduleDotMethod componentsSeparatedByString:@"."];

React/Base/RCTBridgeDelegate.h

@@ -105,6 +105,15 @@
  */
 - (BOOL)shouldBridgeUseCxxBridge:(RCTBridge *)bridge;
 
+/**
+* The bridge will call this method when a module been called from JS
+* cannot be found among registered modules.
+* It should return YES if the module with name 'moduleName' was registered
+* in the implementation, and the system must attempt to look for it again among registered.
+* If the module was not registered, return NO to prevent further searches.
+*/
+- (BOOL)bridge:(RCTBridge *)bridge didNotFindModule:(NSString *)moduleName;
+
 /**
  * The bridge will automatically attempt to load the JS source code from the
  * location specified by the `sourceURLForBridge:` method, however, if you want

React/CxxBridge/RCTCxxBridge.mm

@@ -138,8 +138,8 @@ @implementation RCTCxxBridge
 
   // Native modules
   NSMutableDictionary<NSString *, RCTModuleData *> *_moduleDataByName;
-  NSArray<RCTModuleData *> *_moduleDataByID;
-  NSArray<Class> *_moduleClassesByID;
+  NSMutableArray<RCTModuleData *> *_moduleDataByID;
+  NSMutableArray<Class> *_moduleClassesByID;
   NSUInteger _modulesInitializedOnMainQueue;
   RCTDisplayLink *_displayLink;
 
@@ -195,6 +195,10 @@ - (instancetype)initWithParentBridge:(RCTBridge *)bridge
     _pendingCalls = [NSMutableArray new];
     _displayLink = [RCTDisplayLink new];
 
+    _moduleDataByName = [NSMutableDictionary new];
+    _moduleClassesByID = [NSMutableArray new];
+    _moduleDataByID = [NSMutableArray new];
+
     [RCTBridge setCurrentBridge:self];
   }
   return self;
@@ -275,8 +279,13 @@ - (void)start
 
   dispatch_group_t prepareBridge = dispatch_group_create();
 
+  [_performanceLogger markStartForTag:RCTPLNativeModuleInit];
+
+  [self registerExtraModules];
   // Initialize all native modules that cannot be loaded lazily
-  [self _initModulesWithDispatchGroup:prepareBridge];
+  [self _initModules:RCTGetModuleClasses() withDispatchGroup:prepareBridge lazilyDiscovered:NO];
+
+  [_performanceLogger markStopForTag:RCTPLNativeModuleInit];
 
   // This doesn't really do anything.  The real work happens in initializeBridge.
   _reactInstance.reset(new Instance);
@@ -442,7 +451,16 @@ - (BOOL)moduleIsInitialized:(Class)moduleClass
   [_performanceLogger markStartForTag:RCTPLNativeModulePrepareConfig];
   RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways, @"-[RCTCxxBridge buildModuleRegistry]", nil);
 
-  auto registry = std::make_shared<ModuleRegistry>(createNativeModules(_moduleDataByID, self, _reactInstance));
+  __weak __typeof(self) weakSelf = self;
+  ModuleRegistry::ModuleNotFoundCallback moduleNotFoundCallback = ^bool(const std::string &name) {
+    __strong __typeof(weakSelf) strongSelf = weakSelf;
+    return [strongSelf.delegate respondsToSelector:@selector(bridge:didNotFindModule:)] &&
+           [strongSelf.delegate bridge:strongSelf didNotFindModule:@(name.c_str())];
+  };
+
+  auto registry = std::make_shared<ModuleRegistry>(
+         createNativeModules(_moduleDataByID, self, _reactInstance),
+         moduleNotFoundCallback);
 
   [_performanceLogger markStopForTag:RCTPLNativeModulePrepareConfig];
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
@@ -501,20 +519,66 @@ - (NSArray *)configForModuleName:(NSString *)moduleName
   return moduleData.config;
 }
 
-- (void)_initModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
+- (NSArray<RCTModuleData *> *)registerModulesForClasses:(NSArray<Class> *)moduleClasses
 {
-  [_performanceLogger markStartForTag:RCTPLNativeModuleInit];
+  RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
+                          @"-[RCTCxxBridge initModulesWithDispatchGroup:] autoexported moduleData", nil);
+
+  NSMutableArray<RCTModuleData *> *moduleDataByID = [NSMutableArray arrayWithCapacity:moduleClasses.count];
+  for (Class moduleClass in moduleClasses) {
+    NSString *moduleName = RCTBridgeModuleNameForClass(moduleClass);
+
+    // Don't initialize the old executor in the new bridge.
+    // TODO mhorowitz #10487027: after D3175632 lands, we won't need
+    // this, because it won't be eagerly initialized.
+    if ([moduleName isEqualToString:@"RCTJSCExecutor"]) {
+      continue;
+    }
+
+    // Check for module name collisions
+    RCTModuleData *moduleData = _moduleDataByName[moduleName];
+    if (moduleData) {
+      if (moduleData.hasInstance) {
+        // Existing module was preregistered, so it takes precedence
+        continue;
+      } else if ([moduleClass new] == nil) {
+        // The new module returned nil from init, so use the old module
+        continue;
+      } else if ([moduleData.moduleClass new] != nil) {
+        // Both modules were non-nil, so it's unclear which should take precedence
+        RCTLogError(@"Attempted to register RCTBridgeModule class %@ for the "
+                    "name '%@', but name was already registered by class %@",
+                    moduleClass, moduleName, moduleData.moduleClass);
+      }
+    }
+
+    // Instantiate moduleData
+    // TODO #13258411: can we defer this until config generation?
+    moduleData = [[RCTModuleData alloc] initWithModuleClass:moduleClass bridge:self];
 
+    _moduleDataByName[moduleName] = moduleData;
+    [_moduleClassesByID addObject:moduleClass];
+    [moduleDataByID addObject:moduleData];
+  }
+  [_moduleDataByID addObjectsFromArray:moduleDataByID];
+
+  RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
+
+  return moduleDataByID;
+}
+
+- (void)registerExtraModules
+{
   RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
                           @"-[RCTCxxBridge initModulesWithDispatchGroup:] extraModules", nil);
+
   NSArray<id<RCTBridgeModule>> *extraModules = nil;
-  if (self.delegate) {
-    if ([self.delegate respondsToSelector:@selector(extraModulesForBridge:)]) {
-      extraModules = [self.delegate extraModulesForBridge:_parentBridge];
-    }
+  if ([self.delegate respondsToSelector:@selector(extraModulesForBridge:)]) {
+    extraModules = [self.delegate extraModulesForBridge:_parentBridge];
   } else if (self.moduleProvider) {
     extraModules = self.moduleProvider();
   }
+
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
 
 #if RCT_DEBUG
@@ -524,10 +588,6 @@ - (void)_initModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
   });
 #endif
 
-  NSMutableArray<Class> *moduleClassesByID = [NSMutableArray new];
-  NSMutableArray<RCTModuleData *> *moduleDataByID = [NSMutableArray new];
-  NSMutableDictionary<NSString *, RCTModuleData *> *moduleDataByName = [NSMutableDictionary new];
-
   RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
                           @"-[RCTCxxBridge initModulesWithDispatchGroup:] preinitialized moduleData", nil);
   // Set up moduleData for pre-initialized module instances
@@ -537,7 +597,7 @@ - (void)_initModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
 
     if (RCT_DEBUG) {
       // Check for name collisions between preregistered modules
-      RCTModuleData *moduleData = moduleDataByName[moduleName];
+      RCTModuleData *moduleData = _moduleDataByName[moduleName];
       if (moduleData) {
         RCTLogError(@"Attempted to register RCTBridgeModule class %@ for the "
                     "name '%@', but name was already registered by class %@",
@@ -547,84 +607,60 @@ - (void)_initModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
     }
 
     // Instantiate moduleData container
-    RCTModuleData *moduleData = [[RCTModuleData alloc] initWithModuleInstance:module
-                                                                       bridge:self];
-    moduleDataByName[moduleName] = moduleData;
-    [moduleClassesByID addObject:moduleClass];
-    [moduleDataByID addObject:moduleData];
+    RCTModuleData *moduleData = [[RCTModuleData alloc] initWithModuleInstance:module bridge:self];
+    _moduleDataByName[moduleName] = moduleData;
+    [_moduleClassesByID addObject:moduleClass];
+    [_moduleDataByID addObject:moduleData];
   }
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
+}
 
-  RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
-                          @"-[RCTCxxBridge initModulesWithDispatchGroup:] autoexported moduleData", nil);
-  // Set up moduleData for automatically-exported modules
-  for (Class moduleClass in RCTGetModuleClasses()) {
-    NSString *moduleName = RCTBridgeModuleNameForClass(moduleClass);
+- (void)_initModules:(NSArray<id<RCTBridgeModule>> *)modules
+   withDispatchGroup:(dispatch_group_t)dispatchGroup
+    lazilyDiscovered:(BOOL)lazilyDiscovered
+{
+  RCTAssert(!(RCTIsMainQueue() && lazilyDiscovered), @"Lazy discovery can only happen off the Main Queue");
 
-    // Don't initialize the old executor in the new bridge.
-    // TODO mhorowitz #10487027: after D3175632 lands, we won't need
-    // this, because it won't be eagerly initialized.
-    if ([moduleName isEqual:@"RCTJSCExecutor"]) {
-      continue;
+  // Set up moduleData for automatically-exported modules
+  NSArray<RCTModuleData *> *moduleDataById = [self registerModulesForClasses:modules];
+
+#ifdef RCT_DEBUG
+  if (lazilyDiscovered) {
+    // Lazily discovered modules do not require instantiation here,
+    // as they are not allowed to have pre-instantiated instance
+    // and must not require the main queue.
+    for (RCTModuleData *moduleData in moduleDataById) {
+      RCTAssert(!(moduleData.requiresMainQueueSetup || moduleData.hasInstance),
+        @"Module \'%@\' requires initialization on the Main Queue or has pre-instantiated, which is not supported for the lazily discovered modules.", moduleData.name);
     }
-
-    // Check for module name collisions
-    RCTModuleData *moduleData = moduleDataByName[moduleName];
-    if (moduleData) {
-      if (moduleData.hasInstance) {
-        // Existing module was preregistered, so it takes precedence
-        continue;
-      } else if ([moduleClass new] == nil) {
-        // The new module returned nil from init, so use the old module
-        continue;
-      } else if ([moduleData.moduleClass new] != nil) {
-        // Both modules were non-nil, so it's unclear which should take precedence
-        RCTLogError(@"Attempted to register RCTBridgeModule class %@ for the "
-                    "name '%@', but name was already registered by class %@",
-                    moduleClass, moduleName, moduleData.moduleClass);
+  }
+  else
+#endif
+  {
+    RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
+                            @"-[RCTCxxBridge initModulesWithDispatchGroup:] moduleData.hasInstance", nil);
+    // Dispatch module init onto main thread for those modules that require it
+    // For non-lazily discovered modules we run through the entire set of modules
+    // that we have, otherwise some modules coming from the delegate
+    // or module provider block, will not be properly instantiated.
+    for (RCTModuleData *moduleData in _moduleDataByID) {
+      if (moduleData.hasInstance && (!moduleData.requiresMainQueueSetup || RCTIsMainQueue())) {
+        // Modules that were pre-initialized should ideally be set up before
+        // bridge init has finished, otherwise the caller may try to access the
+        // module directly rather than via `[bridge moduleForClass:]`, which won't
+        // trigger the lazy initialization process. If the module cannot safely be
+        // set up on the current thread, it will instead be async dispatched
+        // to the main thread to be set up in _prepareModulesWithDispatchGroup:.
+        (void)[moduleData instance];
       }
     }
+    RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
 
-    // Instantiate moduleData
-    // TODO #13258411: can we defer this until config generation?
-    moduleData = [[RCTModuleData alloc] initWithModuleClass:moduleClass
-                                                     bridge:self];
-    moduleDataByName[moduleName] = moduleData;
-    [moduleClassesByID addObject:moduleClass];
-    [moduleDataByID addObject:moduleData];
-  }
-  RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
-
-  // Store modules
-  _moduleDataByID = [moduleDataByID copy];
-  _moduleDataByName = [moduleDataByName copy];
-  _moduleClassesByID = [moduleClassesByID copy];
-
-  RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
-                          @"-[RCTCxxBridge initModulesWithDispatchGroup:] moduleData.hasInstance", nil);
-  // Dispatch module init onto main thead for those modules that require it
-  for (RCTModuleData *moduleData in _moduleDataByID) {
-    if (moduleData.hasInstance &&
-        (!moduleData.requiresMainQueueSetup || RCTIsMainQueue())) {
-      // Modules that were pre-initialized should ideally be set up before
-      // bridge init has finished, otherwise the caller may try to access the
-      // module directly rather than via `[bridge moduleForClass:]`, which won't
-      // trigger the lazy initialization process. If the module cannot safely be
-      // set up on the current thread, it will instead be async dispatched
-      // to the main thread to be set up in the loop below.
-      (void)[moduleData instance];
-    }
+    // From this point on, RCTDidInitializeModuleNotification notifications will
+    // be sent the first time a module is accessed.
+    _moduleSetupComplete = YES;
+    [self _prepareModulesWithDispatchGroup:dispatchGroup];
   }
-  RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
-
-  // From this point on, RCTDidInitializeModuleNotification notifications will
-  // be sent the first time a module is accessed.
-  _moduleSetupComplete = YES;
-
-  [self _prepareModulesWithDispatchGroup:dispatchGroup];
-
-  [_performanceLogger markStopForTag:RCTPLNativeModuleInit];
-  RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
 
 #if RCT_PROFILE
   if (RCTProfileIsProfiling()) {
@@ -634,6 +670,11 @@ - (void)_initModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
 #endif
 }
 
+- (void)registerAdditionalModuleClasses:(NSArray<Class> *)modules
+{
+  [self _initModules:modules withDispatchGroup:NULL lazilyDiscovered:YES];
+}
+
 - (void)_prepareModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
 {
   RCT_PROFILE_BEGIN_EVENT(0, @"-[RCTBatchedBridge prepareModulesWithDispatch]", nil);
@@ -655,6 +696,7 @@ - (void)_prepareModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
 
   // Set up modules that require main thread init or constants export
   [_performanceLogger setValue:0 forTag:RCTPLNativeModuleMainThread];
+
   for (RCTModuleData *moduleData in _moduleDataByID) {
     if (whitelistedModules && ![whitelistedModules containsObject:[moduleData moduleClass]]) {
       continue;
@@ -687,7 +729,6 @@ - (void)_prepareModulesWithDispatchGroup:(dispatch_group_t)dispatchGroup
       _modulesInitializedOnMainQueue++;
     }
   }
-
   [_performanceLogger setValue:_modulesInitializedOnMainQueue forTag:RCTPLNativeModuleMainThreadUsesCount];
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
 }

ReactCommon/cxxreact/ModuleRegistry.cpp

@@ -27,8 +27,8 @@ std::string normalizeName(std::string name) {
 
 }
 
-ModuleRegistry::ModuleRegistry(std::vector<std::unique_ptr<NativeModule>> modules)
-    : modules_(std::move(modules)) {}
+ModuleRegistry::ModuleRegistry(std::vector<std::unique_ptr<NativeModule>> modules, ModuleNotFoundCallback callback)
+    : modules_{std::move(modules)}, moduleNotFoundCallback_{callback} {}
 
 void ModuleRegistry::updateModuleNamesFromIndex(size_t index) {
   for (; index < modules_.size(); index++ ) {
@@ -82,13 +82,22 @@ folly::Optional<ModuleConfig> ModuleRegistry::getConfig(const std::string& name)
   }
 
   auto it = modulesByName_.find(name);
+
   if (it == modulesByName_.end()) {
-    unknownModules_.insert(name);
-    return nullptr;
+    if (unknownModules_.find(name) != unknownModules_.end()) {
+      return nullptr;
+    }
+    if (!moduleNotFoundCallback_ ||
+        !moduleNotFoundCallback_(name) ||
+        (it = modulesByName_.find(name)) == modulesByName_.end()) {
+      unknownModules_.insert(name);
+      return nullptr;
+    }
   }
+  size_t index = it->second;
 
-  CHECK(it->second < modules_.size());
-  NativeModule* module = modules_[it->second].get();
+  CHECK(index < modules_.size());
+  NativeModule *module = modules_[index].get();
 
   // string name, object constants, array methodNames (methodId is index), [array promiseMethodIds], [array syncMethodIds]
   folly::dynamic config = folly::dynamic::array(name);
@@ -131,7 +140,7 @@ folly::Optional<ModuleConfig> ModuleRegistry::getConfig(const std::string& name)
     // no constants or methods
     return nullptr;
   } else {
-    return ModuleConfig({it->second, config});
+    return ModuleConfig{index, config};
   }
 }