Fix HMR (#865)

* works on ReduxApp and ReduxSharedStoreApp
* On ReduxSharedStoreApp, only one instance of the component shown twice updates.

spec/dummy/client/.babelrc

@@ -1,3 +1,6 @@
 {
-  "presets": ["es2015", "stage-2", "react"]
+  "presets": [["es2015", {"modules": false}], "stage-2", "react"],
+  "plugins": [
+    "react-hot-loader/babel"
+  ]
 }

spec/dummy/client/app/startup/ClientReduxApp.jsx

@@ -5,7 +5,9 @@
 import React from 'react';
 import { combineReducers, applyMiddleware, createStore } from 'redux';
 import { Provider } from 'react-redux';
-import middleware from 'redux-thunk';
+import thunkMiddleware from 'redux-thunk';
+import { AppContainer } from "react-hot-loader";
+import { render } from "react-dom";
 
 import reducers from '../reducers/reducersIndex';
 import composeInitialState from '../store/composeInitialState';
@@ -18,19 +20,36 @@ import HelloWorldContainer from '../components/HelloWorldContainer';
  *  React will see that the state is the same and not do anything.
  *
  */
-export default (props, railsContext) => {
+export default (props, railsContext, domNodeId) => {
   const combinedReducer = combineReducers(reducers);
   const combinedProps = composeInitialState(props, railsContext);
 
   // This is where we'll put in the middleware for the async function. Placeholder.
   // store will have helloWorldData as a top level property
-  const store = applyMiddleware(middleware)(createStore)(combinedReducer, combinedProps);
+  const store = createStore(combinedReducer, combinedProps, applyMiddleware(thunkMiddleware));
 
-  // Provider uses the this.props.children, so we're not typical React syntax.
+  // renderApp is a function required for hot reloading. see
+  // https://github.com/retroalgic/react-on-rails-hot-minimal/blob/master/client/src/entry.js
+
+  // Provider uses this.props.children, so we're not typical React syntax.
   // This allows redux to add additional props to the HelloWorldContainer.
-  return (
-    <Provider store={store}>
-      <HelloWorldContainer />
-    </Provider>
-  );
+  const renderApp = (Komponent) => {
+    const element = (
+      <AppContainer>
+        <Provider store={store}>
+          <Komponent />
+        </Provider>
+      </AppContainer>
+    )
+    render(element, document.getElementById(domNodeId));
+  }
+
+  renderApp(HelloWorldContainer);
+
+  if (module.hot) {
+    module.hot.accept(['../reducers/reducersIndex', '../components/HelloWorldContainer'], () => {
+      store.replaceReducer(combineReducers(reducers));
+      renderApp(HelloWorldContainer);
+    })
+  }
 };

spec/dummy/client/app/startup/ClientReduxSharedStoreApp.jsx

@@ -4,6 +4,8 @@
 import React from 'react';
 import { Provider } from 'react-redux';
 import ReactOnRails from 'react-on-rails';
+import { AppContainer } from "react-hot-loader";
+import { render } from "react-dom";
 
 import HelloWorldContainer from '../components/HelloWorldContainer';
 
@@ -12,13 +14,31 @@ import HelloWorldContainer from '../components/HelloWorldContainer';
  *  This is used for the client rendering hook after the page html is rendered.
  *  React will see that the state is the same and not do anything.
  */
-export default () => {
+export default (props, railsContext, domNodeId) => {
   // This is where we get the existing store.
   const store = ReactOnRails.getStore('SharedReduxStore');
 
-  return (
-    <Provider store={store}>
-      <HelloWorldContainer />
-    </Provider>
-  );
+  // renderApp is a function required for hot reloading. see
+  // https://github.com/retroalgic/react-on-rails-hot-minimal/blob/master/client/src/entry.js
+
+  // Provider uses this.props.children, so we're not typical React syntax.
+  // This allows redux to add additional props to the HelloWorldContainer.
+  const renderApp = (Komponent) => {
+    const element = (
+      <AppContainer>
+        <Provider store={store}>
+          <Komponent />
+        </Provider>
+      </AppContainer>
+    )
+    render(element, document.getElementById(domNodeId));
+  }
+
+  renderApp(HelloWorldContainer);
+
+  if (module.hot) {
+    module.hot.accept(['../components/HelloWorldContainer'], () => {
+      renderApp(HelloWorldContainer);
+    })
+  }
 };

spec/dummy/client/package.json

@@ -34,7 +34,8 @@
     "react": "^15.5.4",
     "react-dom": "^15.5.4",
     "react-helmet": "^5.0.3",
-    "react-on-rails": "^8.0.1",
+    "react-hot-loader": "^3.0.0-beta.6",
+    "react-on-rails": "8.0.2",
     "react-proptypes": "^0.0.1",
     "react-redux": "^5.0.4",
     "react-router": "3.0.5",
@@ -59,7 +60,6 @@
     "eslint-plugin-react": "^6.10.3",
     "fbjs": "^0.8.12",
     "jsdom": "^9.12.0",
-    "react-transform-hmr": "^1.0.4",
     "tape": "^4.6.3",
     "webpack-dev-server": "^2.4.2"
   },

spec/dummy/client/server-rails-hot.js

@@ -13,10 +13,10 @@
 // 2. Make sure you have a hot-assets target in your client/package.json
 // 3. Start up `foreman start -f Procfile.hot` to start both Rails and the hot reload server.
 
-import webpack from 'webpack';
-import WebpackDevServer from 'webpack-dev-server';
+const webpack = require('webpack');
+const WebpackDevServer = require('webpack-dev-server');
 const { resolve } = require('path');
-import webpackConfig from './webpack.client.rails.hot.config';
+const webpackConfig = require('./webpack.client.rails.hot.config');
 
 const webpackConfigLoader = require('react-on-rails/webpackConfigLoader');
 const configPath = resolve('..', 'config');
@@ -26,6 +26,11 @@ const compiler = webpack(webpackConfig);
 
 const devServer = new WebpackDevServer(compiler, {
   contentBase: hotReloadingUrl,
+  headers: {
+    'Access-Control-Allow-Origin': '*',
+  },
+  disableHostCheck: true,
+  clientLogLevel: 'info',
   hot: true,
   inline: true,
   historyApiFallback: true,

spec/dummy/client/webpack.client.rails.hot.config.js

@@ -3,6 +3,9 @@
 // cd client && babel-node server-rails-hot.js
 // Note that Foreman (Procfile.dev) has also been configured to take care of this.
 
+// require() is used rather than import because hot reloading with webpack
+// requires webpack to transform modules from ES6 to ES5 instead of babel
+// and webpack can not transform its own config files.
 const { resolve } = require('path');
 const webpack = require('webpack');
 const merge = require('webpack-merge');
@@ -11,12 +14,19 @@ const webpackConfigLoader = require('react-on-rails/webpackConfigLoader');
 const configPath = resolve('..', 'config');
 const { hotReloadingUrl, webpackOutputPath } = webpackConfigLoader(configPath);
 
-module.exports = merge(config, {
+// entry is prepended because 'react-hot-loader/patch' must be the very first entry
+// for hot reloading to work.
+module.exports = merge.strategy(
+  {
+    entry: 'prepend'
+  }
+)(config, {
 
   devtool: 'eval-source-map',
 
   entry: {
     'app-bundle': [
+      'react-hot-loader/patch',
       `webpack-dev-server/client?${hotReloadingUrl}`,
       'webpack/hot/only-dev-server'
     ],
@@ -25,6 +35,7 @@ module.exports = merge(config, {
   output: {
     filename: '[name].js',
     path: webpackOutputPath,
+    publicPath: `${hotReloadingUrl}/`,
   },
 
   module: {
@@ -33,22 +44,6 @@ module.exports = merge(config, {
         test: /\.jsx?$/,
         loader: 'babel-loader',
         exclude: /node_modules/,
-        query: {
-          plugins: [
-            [
-              'react-transform',
-              {
-                transforms: [
-                  {
-                    transform: 'react-transform-hmr',
-                    imports: ['react'],
-                    locals: ['module'],
-                  },
-                ],
-              },
-            ],
-          ],
-        },
       },
       {
         test: /\.css$/,
@@ -111,8 +106,13 @@ module.exports = merge(config, {
     ],
   },
 
+// webpack.NamedModulesPlugin() is an optional module that is great for HMR debugging
+// since it transform module IDs (112, 698, etc...) into their respective paths,
+// but it can conflict with other libraries that expect global references. When in doubt, throw it out.
+
   plugins: [
     new webpack.HotModuleReplacementPlugin(),
+    new webpack.NamedModulesPlugin(),
     new webpack.NoEmitOnErrorsPlugin(),
   ],
 });