iOS: allow disabling packager access at runtime

Summary:
Allow disabling packager access based on the app runtime environment, e.g. running tests.

Changelog: [Internal]

Differential Revision: D27903019

fbshipit-source-id: cafa25e93efab3cf8e96d60a8fc03de8abb833f4

Author: fkgozali

React/Base/RCTBundleURLProvider.h

@@ -7,16 +7,19 @@
 
 #import <Foundation/Foundation.h>
 
-#if defined(__cplusplus)
-extern "C" {
-#endif
-
-extern NSString *const RCTBundleURLProviderUpdatedNotification;
+#import "RCTDefines.h"
 
-extern const NSUInteger kRCTBundleURLProviderDefaultPort;
+RCT_EXTERN NSString *const RCTBundleURLProviderUpdatedNotification;
+RCT_EXTERN const NSUInteger kRCTBundleURLProviderDefaultPort;
 
-#if defined(__cplusplus)
-}
+#if RCT_DEV_MENU
+/**
+ * Allow/disallow accessing the packager server for various runtime scenario.
+ * For instance, if a test run should never access the packager, disable it
+ * by calling this function before initializing React Native (RCTBridge etc).
+ * By default the access is enabled.
+ */
+RCT_EXTERN void RCTBundleURLProviderAllowPackagerServerAccess(BOOL allowed);
 #endif
 
 @interface RCTBundleURLProvider : NSObject

React/Base/RCTBundleURLProvider.mm

@@ -9,11 +9,20 @@
 
 #import "RCTConvert.h"
 #import "RCTDefines.h"
+#import "RCTLog.h"
 
 NSString *const RCTBundleURLProviderUpdatedNotification = @"RCTBundleURLProviderUpdatedNotification";
 
 const NSUInteger kRCTBundleURLProviderDefaultPort = RCT_METRO_PORT;
 
+#if RCT_DEV_MENU
+static BOOL kRCTAllowPackagerAccess = YES;
+void RCTBundleURLProviderAllowPackagerServerAccess(BOOL allowed)
+{
+  kRCTAllowPackagerAccess = allowed;
+}
+#endif
+
 static NSString *const kRCTJsLocationKey = @"RCT_jsLocation";
 static NSString *const kRCTEnableDevKey = @"RCT_enableDev";
 static NSString *const kRCTEnableMinificationKey = @"RCT_enableMinification";
@@ -127,6 +136,12 @@ - (NSString *)packagerServerHost
 
 - (NSString *)packagerServerHostPort
 {
+#if RCT_DEV_MENU
+  if (!kRCTAllowPackagerAccess) {
+    RCTLogInfo(@"Packager server access is disabled in this environment");
+    return nil;
+  }
+#endif
   NSString *location = [self jsLocation];
 #if RCT_DEV_MENU
   if ([location length] && ![RCTBundleURLProvider isPackagerRunning:location]) {