Fix edge case in /_app HMR. Fixes #4620

Author: timneutkens

client/webpack-hot-middleware-client.js

@@ -4,6 +4,12 @@ import Router from '../lib/router'
 
 const handlers = {
   reload (route) {
+    // If the App component changes we have to reload the current route, this is handled by hot-self-accept-loader
+    // So we just return
+    if (route === '/_app') {
+      return
+    }
+
     if (route === '/_error') {
       for (const r of Object.keys(Router.components)) {
         const { err } = Router.components[r]
@@ -16,12 +22,6 @@ const handlers = {
       return
     }
 
-    // If the App component changes we have to reload the current route
-    if (route === '/_app') {
-      Router.reload(Router.route)
-      return
-    }
-
     // Since _document is server only we need to reload the full page when it changes.
     if (route === '/_document') {
       window.location.reload()
@@ -32,9 +32,9 @@ const handlers = {
   },
 
   change (route) {
-    // If the App component changes we have to reload the current route
+    // If the App component changes we have to reload the current route, this is handled by hot-self-accept-loader
+    // So we just return
     if (route === '/_app') {
-      Router.reload(Router.route)
       return
     }