Tweak HMR updates order

Reviewed By: sam-swarr

Differential Revision: D3007914

fb-gh-sync-id: efceeeafdaaf82e47ee2d2e8a313b64694988b5c
shipit-source-id: efceeeafdaaf82e47ee2d2e8a313b64694988b5c

local-cli/server/util/attachHMRServer.js

@@ -174,6 +174,16 @@ function attachHMRServer({httpServer, path, packagerServer}) {
                       }
                     });
 
+                    // Need to send modules to the client in an order it can
+                    // process them: if a new dependency graph was uncovered
+                    // because a new dependency was added, the file that was
+                    // changed, which is the root of the dependency tree that
+                    // will be sent, needs to be the last module that gets
+                    // processed. Reversing the new modules makes sense
+                    // because we get them through the resolver which returns
+                    // a BFS ordered list.
+                    modulesToUpdate.reverse();
+
                     // invalidate caches
                     client.dependenciesCache = dependenciesCache;
                     client.dependenciesModulesCache = dependenciesModulesCache;