Fix fetching sourcemap in genymotion. Fixes #5338

Summary:Source maps are broken on Genymotion right now as they aren't being loaded from the correct URL. refer - https://github.com/facebook/react-native/issues/5338#issuecomment-188232402

**Test plan**

Build and install UIExplorer from master branch in genymotion and enable hot reload. When you change a file and save it, you'll see a Yellow box due to source map fetching failed, as per the referenced comment.

Doing the same for this branch doesn't produce any yellow boxes.
Closes https://github.com/facebook/react-native/pull/6594

Differential Revision: D3088218

Pulled By: martinbigio

fb-gh-sync-id: 0d1c19cc263de5c6c62061c399eef33fa4ac4a7b
shipit-source-id: 0d1c19cc263de5c6c62061c399eef33fa4ac4a7b

ReactAndroid/src/main/java/com/facebook/react/devsupport/BUCK

@@ -9,6 +9,7 @@ android_library(
     react_native_target('java/com/facebook/react/bridge:bridge'),
     react_native_target('java/com/facebook/react/common:common'),
     react_native_target('java/com/facebook/react/modules/debug:debug'),
+    react_native_target('java/com/facebook/react/modules/systeminfo:systeminfo'),
     react_native_dep('libraries/fbcore/src/main/java/com/facebook/common/logging:logging'),
     react_native_dep('third-party/java/infer-annotations:infer-annotations'),
     react_native_dep('third-party/java/jsr-305:jsr-305'),

ReactAndroid/src/main/java/com/facebook/react/devsupport/DevServerHelper.java

@@ -9,16 +9,7 @@
 
 package com.facebook.react.devsupport;
 
-import javax.annotation.Nullable;
-
-import java.io.File;
-import java.io.IOException;
-import java.net.URL;
-import java.util.Locale;
-import java.util.concurrent.TimeUnit;
-
 import android.content.Context;
-import android.os.Build;
 import android.os.Handler;
 import android.text.TextUtils;
 
@@ -26,6 +17,7 @@ import com.facebook.common.logging.FLog;
 import com.facebook.infer.annotation.Assertions;
 import com.facebook.react.bridge.UiThreadUtil;
 import com.facebook.react.common.ReactConstants;
+import com.facebook.react.modules.systeminfo.AndroidInfoHelpers;
 import com.squareup.okhttp.Call;
 import com.squareup.okhttp.Callback;
 import com.squareup.okhttp.ConnectionPool;
@@ -34,6 +26,13 @@ import com.squareup.okhttp.Request;
 import com.squareup.okhttp.Response;
 import com.squareup.okhttp.ResponseBody;
 
+import java.io.File;
+import java.io.IOException;
+import java.util.Locale;
+import java.util.concurrent.TimeUnit;
+
+import javax.annotation.Nullable;
+
 import okio.Okio;
 import okio.Sink;
 
@@ -51,10 +50,6 @@ public class DevServerHelper {
   public static final String RELOAD_APP_EXTRA_JS_PROXY = "jsproxy";
   private static final String RELOAD_APP_ACTION_SUFFIX = ".RELOAD_APP_ACTION";
 
-  private static final String EMULATOR_LOCALHOST = "10.0.2.2:8081";
-  private static final String GENYMOTION_LOCALHOST = "10.0.3.2:8081";
-  private static final String DEVICE_LOCALHOST = "localhost:8081";
-
   private static final String BUNDLE_URL_FORMAT =
       "http://%s/%s.bundle?platform=android&dev=%s&hot=%s&minify=%s";
   private static final String SOURCE_MAP_URL_FORMAT =
@@ -118,7 +113,7 @@ public class DevServerHelper {
    * @return the host to use when connecting to the bundle server from the host itself.
    */
   private static String getHostForJSProxy() {
-    return DEVICE_LOCALHOST;
+    return AndroidInfoHelpers.DEVICE_LOCALHOST;
   }
 
   /**
@@ -149,31 +144,21 @@ public class DevServerHelper {
     // Check debug server host setting first. If empty try to detect emulator type and use default
     // hostname for those
     String hostFromSettings = mSettings.getDebugServerHost();
+
     if (!TextUtils.isEmpty(hostFromSettings)) {
       return Assertions.assertNotNull(hostFromSettings);
     }
 
-    // Since genymotion runs in vbox it use different hostname to refer to adb host.
-    // We detect whether app runs on genymotion and replace js bundle server hostname accordingly
-    if (isRunningOnGenymotion()) {
-      return GENYMOTION_LOCALHOST;
-    }
-    if (isRunningOnStockEmulator()) {
-      return EMULATOR_LOCALHOST;
-    }
-    FLog.w(
+    String host = AndroidInfoHelpers.getServerHost();
+
+    if (host.equals(AndroidInfoHelpers.DEVICE_LOCALHOST)) {
+      FLog.w(
         ReactConstants.TAG,
         "You seem to be running on device. Run 'adb reverse tcp:8081 tcp:8081' " +
-            "to forward the debug server's port to the device.");
-    return DEVICE_LOCALHOST;
-  }
+          "to forward the debug server's port to the device.");
+    }
 
-  private boolean isRunningOnGenymotion() {
-    return Build.FINGERPRINT.contains("vbox");
-  }
-
-  private boolean isRunningOnStockEmulator() {
-    return Build.FINGERPRINT.contains("generic");
+    return host;
   }
 
   private static String createBundleURL(String host, String jsModulePath, boolean devMode, boolean hmr, boolean jsMinify) {

ReactAndroid/src/main/java/com/facebook/react/modules/systeminfo/AndroidInfoHelpers.java

@@ -0,0 +1,33 @@
+package com.facebook.react.modules.systeminfo;
+
+import android.os.Build;
+
+public class AndroidInfoHelpers {
+
+  public static final String EMULATOR_LOCALHOST = "10.0.2.2:8081";
+  public static final String GENYMOTION_LOCALHOST = "10.0.3.2:8081";
+  public static final String DEVICE_LOCALHOST = "localhost:8081";
+
+  private static boolean isRunningOnGenymotion() {
+    return Build.FINGERPRINT.contains("vbox");
+  }
+
+  private static boolean isRunningOnStockEmulator() {
+    return Build.FINGERPRINT.contains("generic");
+  }
+
+  public static String getServerHost() {
+    // Since genymotion runs in vbox it use different hostname to refer to adb host.
+    // We detect whether app runs on genymotion and replace js bundle server hostname accordingly
+
+    if (isRunningOnGenymotion()) {
+      return GENYMOTION_LOCALHOST;
+    }
+
+    if (isRunningOnStockEmulator()) {
+      return EMULATOR_LOCALHOST;
+    }
+
+    return DEVICE_LOCALHOST;
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/modules/systeminfo/AndroidInfoModule.java

@@ -9,14 +9,14 @@
 
 package com.facebook.react.modules.systeminfo;
 
-import javax.annotation.Nullable;
+import android.os.Build;
+
+import com.facebook.react.bridge.BaseJavaModule;
 
 import java.util.HashMap;
 import java.util.Map;
 
-import android.os.Build;
-
-import com.facebook.react.bridge.BaseJavaModule;
+import javax.annotation.Nullable;
 
 /**
  * Module that exposes Android Constants to JS.
@@ -32,6 +32,7 @@ public class AndroidInfoModule extends BaseJavaModule {
   public @Nullable Map<String, Object> getConstants() {
     HashMap<String, Object> constants = new HashMap<String, Object>();
     constants.put("Version", Build.VERSION.SDK_INT);
+    constants.put("ServerHost", AndroidInfoHelpers.getServerHost());
     return constants;
   }
 }