Make HMR faster (2)

Summary:
public

The HMR listener needs to be invoked on the non debounced callback to avoid loosing updates if 2 files are updated within the debounce configured time.

Also, improve the time it takes to send HMR updates by avoiding rebuilding the bundle when the listener is defined. Instead just invalidate the bundles cache so that if the user reloads or disables Hot Loading the packager rebuilds the requested bundle.

Reviewed By: davidaurelio

Differential Revision: D2863141

fb-gh-sync-id: 3ab500eacbd4a2e4b63619755e5eabf8afdd1db9

local-cli/server/util/attachHMRServer.js

@@ -109,10 +109,10 @@ function attachHMRServer({httpServer, path, packagerServer}) {
 
         packagerServer.setHMRFileChangeListener((filename, stat) => {
           if (!client) {
-            return Promise.resolve();
+            return;
           }
 
-          return stat.then(() => {
+          stat.then(() => {
             return packagerServer.getShallowDependencies(filename)
               .then(deps => {
                 if (!client) {