tighter ContextContainer semantics

Summary:
shergin mentioned that he'd like to move away from RTTI a bit and use explicit key strings for context container instances rather than relying on the `typeid`, so this does this.

We also fatal with a useful error message if we get a collision, rather than failing silently.

Reviewed By: shergin

Differential Revision: D13384308

fbshipit-source-id: 0b06d7555b082be89e8f130c23e94be99749a7a3

React/Fabric/RCTSurfacePresenter.mm

@@ -189,7 +189,7 @@ using namespace facebook::react;
 
   _contextContainer = std::make_shared<ContextContainer>();
 
-  _contextContainer->registerInstance(_reactNativeConfig);
+  _contextContainer->registerInstance(_reactNativeConfig, "ReactNativeConfig");
 
   auto messageQueueThread = _batchedBridge.jsMessageThread;
   auto runtime = (facebook::jsi::Runtime *)((RCTCxxBridge *)_batchedBridge).runtime;
@@ -214,7 +214,7 @@ using namespace facebook::react;
 
   _contextContainer->registerInstance(runtimeExecutor, "runtime-executor");
 
-  _contextContainer->registerInstance(std::make_shared<ImageManager>((__bridge void *)[_bridge imageLoader]));
+  _contextContainer->registerInstance(std::make_shared<ImageManager>((__bridge void *)[_bridge imageLoader]), "ImageManager");
   return _contextContainer;
 }
 

ReactCommon/fabric/components/image/ImageComponentDescriptor.h

@@ -27,7 +27,8 @@ class ImageComponentDescriptor final
       : ConcreteComponentDescriptor(eventDispatcher),
         imageManager_(
             contextContainer
-                ? contextContainer->getInstance<SharedImageManager>()
+                ? contextContainer->getInstance<SharedImageManager>(
+                      "ImageManager")
                 : nullptr) {}
 
   void adopt(UnsharedShadowNode shadowNode) const override {

ReactCommon/fabric/uimanager/ContextContainer.h

@@ -27,36 +27,39 @@ using SharedContextContainer = std::shared_ptr<ContextContainer>;
 class ContextContainer final {
  public:
   /*
-   * Registers an instance of the particular type `T` in the container.
+   * Registers an instance of the particular type `T` in the container
-   * If `key` parameter is specified, the instance is registered
+   * using the provided `key`. Only one instance can be registered per key.
-   * by `{type, key}` pair.
+   *
+   * Convention is to use the plain base class name for the key, so for
+   * example if the type `T` is `std::shared_ptr<const ReactNativeConfig>`,
+   * then one would use `"ReactNativeConfig"` for the `key`, even if the
+   * instance is actually a `shared_ptr` of derived class
+   *`EmptyReactNativeConfig`.
    */
   template <typename T>
-  void registerInstance(const T &instance, const std::string &key = {}) {
+  void registerInstance(const T &instance, const std::string &key) {
     std::lock_guard<std::mutex> lock(mutex_);
 
-    instances_.insert(
+    const auto res = instances_.insert({key, std::make_shared<T>(instance)});
-        {{std::type_index(typeid(T)), key}, std::make_shared<T>(instance)});
+    if (res.second == false) {
+      LOG(FATAL) << "ContextContainer already had instance for key '" << key
+                 << "'";
+    }
   }
 
   /*
-   * Returns a previously registered instance of the particular type `T`.
+   * Returns a previously registered instance of the particular type `T`
-   * If `key` parameter is specified, the lookup will be performed
+   * for `key`.
-   * by {type, key} pair.
    */
   template <typename T>
-  T getInstance(const std::string &key = {}) const {
+  T getInstance(const std::string &key) const {
     std::lock_guard<std::mutex> lock(mutex_);
 
-    return *std::static_pointer_cast<T>(
+    return *std::static_pointer_cast<T>(instances_.at(key));
-        instances_.at({std::type_index(typeid(T)), key}));
   }
 
  private:
-  std::unordered_map<
+  std::unordered_map<std::string, std::shared_ptr<void>> instances_;
-      std::pair<std::type_index, std::string>,
-      std::shared_ptr<void>>
-      instances_;
 
   mutable std::mutex mutex_;
 };

ReactCommon/fabric/uimanager/Scheduler.cpp

@@ -28,7 +28,8 @@ Scheduler::Scheduler(const SharedContextContainer &contextContainer) {
       contextContainer->getInstance<RuntimeExecutor>("runtime-executor");
 
   reactNativeConfig_ =
-      contextContainer->getInstance<std::shared_ptr<const ReactNativeConfig>>();
+      contextContainer->getInstance<std::shared_ptr<const ReactNativeConfig>>(
+          "ReactNativeConfig");
 
   auto uiManager = std::make_unique<UIManager>();
   auto &uiManagerRef = *uiManager;