Don't hardcode 'localhost:8081' as the _hmrURL in the Bundler

Summary:martinbigio this fixes your TODO. 🚀 🚀 🚀
Closes facebook#5827

Differential Revision: D2932188

Pulled By: martinbigio

fb-gh-sync-id: 8c8caf0782f05b51c90c8d09fdb743ddd3e6f97e
shipit-source-id: 8c8caf0782f05b51c90c8d09fdb743ddd3e6f97e

Author: skevy

local-cli/server/util/attachHMRServer.js

@@ -185,11 +185,23 @@ function attachHMRServer({httpServer, path, packagerServer}) {
                   return;
                 }
 
+                const httpServerAddress = httpServer.address();
+
+                // Sanitize the value from the HTTP server
+                let packagerHost = 'localhost';
+                if (httpServer.address().address &&
+                    httpServer.address().address !== '::' &&
+                    httpServer.address().address !== '') {
+                  packagerHost = httpServerAddress.address;
+                }
+
+                let packagerPort = httpServerAddress.port;
+
                 return packagerServer.buildBundleForHMR({
                   entryFile: client.bundleEntry,
                   platform: client.platform,
                   resolutionResponse,
-                });
+                }, packagerHost, packagerPort);
               })
               .then(bundle => {
                 if (!client || !bundle || bundle.isEmpty()) {

packager/react-packager/src/Bundler/index.js

@@ -168,9 +168,9 @@ class Bundler {
     });
   }
 
-  _sourceHMRURL(platform, path) {
+  _sourceHMRURL(platform, host, port, path) {
     return this._hmrURL(
-      'http://localhost:8081', // TODO: (martinb) avoid hardcoding
+      `http://${host}:${port}`,
       platform,
       'bundle',
       path,
@@ -211,10 +211,10 @@ class Bundler {
     );
   }
 
-  hmrBundle(options) {
+  hmrBundle(options, host, port) {
     return this._bundle({
       bundle: new HMRBundle({
-        sourceURLFn: this._sourceHMRURL.bind(this, options.platform),
+        sourceURLFn: this._sourceHMRURL.bind(this, options.platform, host, port),
         sourceMappingURLFn: this._sourceMappingHMRURL.bind(
           this,
           options.platform,

packager/react-packager/src/Server/index.js

@@ -240,8 +240,8 @@ class Server {
     return this.buildBundle(options);
   }
 
-  buildBundleForHMR(modules) {
-    return this._bundler.hmrBundle(modules);
+  buildBundleForHMR(modules, host, port) {
+    return this._bundler.hmrBundle(modules, host, port);
   }
 
   getShallowDependencies(entryFile) {