new-webpack: copy prod config to new shared config (#562)

Summary:
This module will become the shared home of the production and
development configurations.

Test Plan:
Run:

```
rm -r build/
NODE_ENV=production node node_modules/.bin/webpack \
    --config config/makeWebpackConfig.js
(cd build && python -m SimpleHTTPServer)
```

and load http://localhost:8000. Note that the main content of app still
works, although the static assets in the SourceCred directory are not
loaded so the useful functionality is crippled.

wchargin-branch: webpack-init

config/makeWebpackConfig.js

@@ -0,0 +1,248 @@
+// @no-flow
+const path = require("path");
+const webpack = require("webpack");
+const ManifestPlugin = require("webpack-manifest-plugin");
+const SWPrecacheWebpackPlugin = require("sw-precache-webpack-plugin");
+const StaticSiteGeneratorPlugin = require("static-site-generator-webpack-plugin");
+const eslintFormatter = require("react-dev-utils/eslintFormatter");
+const ModuleScopePlugin = require("react-dev-utils/ModuleScopePlugin");
+const paths = require("./paths");
+const getClientEnvironment = require("./env");
+
+// Webpack uses `publicPath` to determine where the app is being served from.
+// It requires a trailing slash, or the file assets will get an incorrect path.
+const publicPath = paths.servedPath;
+// Source maps are resource heavy and can cause out of memory issue for large source files.
+const shouldUseSourceMap = process.env.GENERATE_SOURCEMAP !== "false";
+// `publicUrl` is just like `publicPath`, but we will provide it to our app
+// as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
+// Omit trailing slash as %PUBLIC_URL%/xyz looks better than %PUBLIC_URL%xyz.
+const publicUrl = publicPath.slice(0, -1);
+// Get environment variables to inject into our app.
+const env = getClientEnvironment(publicUrl);
+
+// Assert this just to be safe.
+// Development builds of React are slow and not intended for production.
+if (env.stringified["process.env"].NODE_ENV !== '"production"') {
+  throw new Error("Production builds must have NODE_ENV=production.");
+}
+
+// This is the production configuration.
+// It compiles slowly and is focused on producing a fast and minimal bundle.
+// The development configuration is different and lives in a separate file.
+module.exports = {
+  // Don't attempt to continue if there are any errors.
+  bail: true,
+  // We generate sourcemaps in production. This is slow but gives good results.
+  // You can exclude the *.map files from the build during deployment.
+  devtool: shouldUseSourceMap ? "source-map" : false,
+  // In production, we only want to load the polyfills and the app code.
+  entry: {
+    main: [require.resolve("./polyfills"), paths.appIndexJs],
+    ssr: [require.resolve("./polyfills"), paths.appServerSideRenderingIndexJs],
+  },
+  output: {
+    // The build folder.
+    path: paths.appBuild,
+    // Generated JS file names (with nested folders).
+    // There will be one main bundle, and one file per asynchronous chunk.
+    // We don't currently advertise code splitting but Webpack supports it.
+    filename: "static/js/[name].[chunkhash:8].js",
+    chunkFilename: "static/js/[name].[chunkhash:8].chunk.js",
+    // We inferred the "public path" (such as / or /my-project) from homepage.
+    publicPath: publicPath,
+    // Point sourcemap entries to original disk location (format as URL on Windows)
+    devtoolModuleFilenameTemplate: (info) =>
+      path
+        .relative(paths.appSrc, info.absoluteResourcePath)
+        .replace(/\\/g, "/"),
+    // We need to use a UMD module to build the static site.
+    libraryTarget: "umd",
+  },
+  resolve: {
+    // This allows you to set a fallback for where Webpack should look for modules.
+    // We placed these paths second because we want `node_modules` to "win"
+    // if there are any conflicts. This matches Node resolution mechanism.
+    // https://github.com/facebookincubator/create-react-app/issues/253
+    modules: ["node_modules", paths.appNodeModules].concat(
+      // It is guaranteed to exist because we tweak it in `env.js`
+      process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
+    ),
+    // These are the reasonable defaults supported by the Node ecosystem.
+    // We also include JSX as a common component filename extension to support
+    // some tools, although we do not recommend using it, see:
+    // https://github.com/facebookincubator/create-react-app/issues/290
+    // `web` extension prefixes have been added for better support
+    // for React Native Web.
+    extensions: [".web.js", ".mjs", ".js", ".json", ".web.jsx", ".jsx"],
+    alias: {
+      // Support React Native Web
+      // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
+      "react-native": "react-native-web",
+    },
+    plugins: [
+      // Prevents users from importing files from outside of src/ (or node_modules/).
+      // This often causes confusion because we only process files within src/ with babel.
+      // To fix this, we prevent you from importing files out of src/ -- if you'd like to,
+      // please link the files into your node_modules/ and let module-resolution kick in.
+      // Make sure your source files are compiled, as they will not be processed in any way.
+      new ModuleScopePlugin(paths.appSrc, [paths.appPackageJson]),
+    ],
+  },
+  module: {
+    strictExportPresence: true,
+    rules: [
+      // TODO: Disable require.ensure as it's not a standard language feature.
+      // We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
+      // { parser: { requireEnsure: false } },
+
+      // First, run the linter.
+      // It's important to do this before Babel processes the JS.
+      {
+        test: /\.(js|jsx|mjs)$/,
+        enforce: "pre",
+        use: [
+          {
+            options: {
+              formatter: eslintFormatter,
+              eslintPath: require.resolve("eslint"),
+            },
+            loader: require.resolve("eslint-loader"),
+          },
+        ],
+        include: paths.appSrc,
+      },
+      {
+        // "oneOf" will traverse all following loaders until one will
+        // match the requirements. When no loader matches it will fall
+        // back to the "file" loader at the end of the loader list.
+        oneOf: [
+          // "url" loader works just like "file" loader but it also embeds
+          // assets smaller than specified size as data URLs to avoid requests.
+          {
+            test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
+            loader: require.resolve("url-loader"),
+            options: {
+              limit: 10000,
+              name: "static/media/[name].[hash:8].[ext]",
+            },
+          },
+          // Process JS with Babel.
+          {
+            test: /\.(js|jsx|mjs)$/,
+            include: paths.appSrc,
+            loader: require.resolve("babel-loader"),
+            options: {
+              compact: true,
+            },
+          },
+          {
+            test: /\.css$/,
+            loader: "css-loader", // TODO(@wchargin): add csso-loader
+          },
+          // "file" loader makes sure assets end up in the `build` folder.
+          // When you `import` an asset, you get its filename.
+          // This loader doesn't use a "test" so it will catch all modules
+          // that fall through the other loaders.
+          {
+            loader: require.resolve("file-loader"),
+            // Exclude `js` files to keep "css" loader working as it injects
+            // it's runtime that would otherwise processed through "file" loader.
+            // Also exclude `html` and `json` extensions so they get processed
+            // by webpacks internal loaders.
+            exclude: [/\.(js|jsx|mjs)$/, /\.html$/, /\.json$/],
+            options: {
+              name: "static/media/[name].[hash:8].[ext]",
+            },
+          },
+          // ** STOP ** Are you adding a new loader?
+          // Make sure to add the new loader(s) before the "file" loader.
+        ],
+      },
+    ],
+  },
+  plugins: [
+    new StaticSiteGeneratorPlugin({
+      entry: "ssr",
+      paths: require(paths.appRouteData).routeData.map(({path}) => path),
+      locals: {},
+    }),
+    // Makes some environment variables available to the JS code, for example:
+    // if (process.env.NODE_ENV === 'production') { ... }. See `./env.js`.
+    // It is absolutely essential that NODE_ENV was set to production here.
+    // Otherwise React will be compiled in the very slow development mode.
+    new webpack.DefinePlugin(env.stringified),
+    // Minify the code.
+    new webpack.optimize.UglifyJsPlugin({
+      compress: {
+        warnings: false,
+        // Disabled because of an issue with Uglify breaking seemingly valid code:
+        // https://github.com/facebookincubator/create-react-app/issues/2376
+        // Pending further investigation:
+        // https://github.com/mishoo/UglifyJS2/issues/2011
+        comparisons: false,
+      },
+      mangle: {
+        safari10: true,
+      },
+      output: {
+        comments: false,
+        // Turned on because emoji and regex is not minified properly using default
+        // https://github.com/facebookincubator/create-react-app/issues/2488
+        ascii_only: true,
+      },
+      sourceMap: shouldUseSourceMap,
+    }),
+    // Generate a manifest file which contains a mapping of all asset filenames
+    // to their corresponding output file so that tools can pick it up without
+    // having to parse `index.html`.
+    new ManifestPlugin({
+      fileName: "asset-manifest.json",
+    }),
+    // Generate a service worker script that will precache, and keep up to date,
+    // the HTML & assets that are part of the Webpack build.
+    new SWPrecacheWebpackPlugin({
+      // By default, a cache-busting query parameter is appended to requests
+      // used to populate the caches, to ensure the responses are fresh.
+      // If a URL is already hashed by Webpack, then there is no concern
+      // about it being stale, and the cache-busting can be skipped.
+      dontCacheBustUrlsMatching: /\.\w{8}\./,
+      filename: "service-worker.js",
+      logger(message) {
+        if (message.indexOf("Total precache size is") === 0) {
+          // This message occurs for every build and is a bit too noisy.
+          return;
+        }
+        if (message.indexOf("Skipping static resource") === 0) {
+          // This message obscures real errors so we ignore it.
+          // https://github.com/facebookincubator/create-react-app/issues/2612
+          return;
+        }
+        console.log(message);
+      },
+      minify: true,
+      // For unknown URLs, fallback to the index page
+      navigateFallback: publicUrl + "/index.html",
+      // Ignores URLs starting from /__ (useful for Firebase):
+      // https://github.com/facebookincubator/create-react-app/issues/2237#issuecomment-302693219
+      navigateFallbackWhitelist: [/^(?!\/__).*/],
+      // Don't precache sourcemaps (they're large) and build asset manifest:
+      staticFileGlobsIgnorePatterns: [/\.map$/, /asset-manifest\.json$/],
+    }),
+    // Moment.js is an extremely popular library that bundles large locale files
+    // by default due to how Webpack interprets its code. This is a practical
+    // solution that requires the user to opt into importing specific locales.
+    // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
+    // You can remove this if you don't use Moment.js:
+    new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/),
+  ],
+  // Some libraries import Node modules but don't use them in the browser.
+  // Tell Webpack to provide empty mocks for them so importing them works.
+  node: {
+    dgram: "empty",
+    fs: "empty",
+    net: "empty",
+    tls: "empty",
+    child_process: "empty",
+  },
+};