Introduce RCTBundleManager

Summary:
NativeModules can read from, or write to, the bridge's bundleURL. To do so, they access the bundleURL property on the bridge directly.
**Setter:**
https://www.internalfb.com/code/fbsource/[2a74581dfff31febe6e91c5739294705f5244ecb]/xplat/js/react-native-github/React/CoreModules/RCTDevMenu.mm?lines=213-214

**Getter:**
https://www.internalfb.com/code/fbsource/[2a74581dfff31febe6e91c5739294705f5244ecb]/xplat/js/react-native-github/React/CoreModules/RCTDevMenu.mm?lines=245%2C256

In bridgeless mode, the bridge is nil. So, this form of access will fail.

After this stack lands, every NativeModule will be able to synthesize an RCTBundleManager, like so:
```
synthesize bundleManager = _bundleManager;
```

From then on, all NativeModules will use this bundleManager to access the bundle URL. This should ensure that NativeModules can read from/write to the bundleURL, **even in bridgeless mode**.

Changelog: [iOS][Added] - Introduce RCTBundleManager for bundleURL access

Reviewed By: PeteTheHeat

Differential Revision: D28086318

fbshipit-source-id: 34c15bf05c144341aa912fad9aa25d6d3a364f9e

Author: RSNara

React/Base/RCTBridgeModule.h

@@ -14,6 +14,7 @@
 @protocol RCTBridgeMethod;
 @class RCTModuleRegistry;
 @class RCTViewRegistry;
+@class RCTBundleManager;
 
 /**
  * The type of a block that is capable of sending a response to a bridged
@@ -135,6 +136,16 @@ RCT_EXTERN_C_END
  */
 @property (nonatomic, weak, readwrite) RCTViewRegistry *viewRegistry_DEPRECATED;
 
+/**
+ * A reference to the RCTBundleManager. Useful for modules that need to read
+ * or write to the app's bundle URL.
+ *
+ * To implement this in your module, just add `@synthesize bundleManager =
+ * _bundleManager;`. If using Swift, add `@objc var bundleManager:
+ * RCTBundleManager!` to your module.
+ */
+@property (nonatomic, weak, readwrite) RCTBundleManager *bundleManager;
+
 /**
  * A reference to the RCTBridge. Useful for modules that require access
  * to bridge features, such as sending events or making JS calls. This
@@ -406,6 +417,19 @@ RCT_EXTERN_C_END
 - (id)moduleForName:(const char *)moduleName lazilyLoadIfNecessary:(BOOL)lazilyLoad;
 @end
 
+typedef void (^RCTBridgelessBundleURLSetter)(NSURL *bundleURL);
+typedef NSURL * (^RCTBridgelessBundleURLGetter)();
+
+/**
+ * A class that allows NativeModules/TurboModules to read/write the bundleURL, with or without the bridge.
+ */
+@interface RCTBundleManager : NSObject
+- (void)setBridge:(RCTBridge *)bridge;
+- (void)setBridgelessBundleURLGetter:(RCTBridgelessBundleURLGetter)getter
+                           andSetter:(RCTBridgelessBundleURLSetter)setter;
+@property NSURL *bundleURL;
+@end
+
 typedef UIView * (^RCTBridgelessComponentViewProvider)(NSNumber *);
 
 /**

React/Base/RCTBundleManager.m

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import "RCTAssert.h"
+#import "RCTBridge+Private.h"
+#import "RCTBridge.h"
+#import "RCTBridgeModule.h"
+
+@implementation RCTBundleManager {
+  __weak RCTBridge *_bridge;
+  RCTBridgelessBundleURLGetter _bridgelessBundleURLGetter;
+  RCTBridgelessBundleURLSetter _bridgelessBundleURLSetter;
+}
+
+- (void)setBridge:(RCTBridge *)bridge
+{
+  _bridge = bridge;
+}
+
+- (void)setBridgelessBundleURLGetter:(RCTBridgelessBundleURLGetter)getter andSetter:(RCTBridgelessBundleURLSetter)setter
+{
+  _bridgelessBundleURLGetter = getter;
+  _bridgelessBundleURLSetter = setter;
+}
+
+- (void)setBundleURL:(NSURL *)bundleURL
+{
+  if (_bridge) {
+    _bridge.bundleURL = bundleURL;
+    return;
+  }
+
+  RCTAssert(
+      _bridgelessBundleURLSetter != nil,
+      @"RCTBundleManager: In bridgeless mode, RCTBridgelessBundleURLSetter must not be nil.");
+  _bridgelessBundleURLSetter(bundleURL);
+}
+
+- (NSURL *)bundleURL
+{
+  if (_bridge) {
+    return _bridge.bundleURL;
+  }
+
+  RCTAssert(
+      _bridgelessBundleURLGetter != nil,
+      @"RCTBundleManager: In bridgeless mode, RCTBridgelessBundleURLGetter must not be nil.");
+
+  return _bridgelessBundleURLGetter();
+}
+
+@end