Speed up TypeScript projects (#5903)

As a lot of [people](https://hackernoon.com/why-i-no-longer-use-typescript-with-react-and-why-you-shouldnt-either-e744d27452b4) is complaining about TypeScript performance in CRA, I decided to enable `async` mode in TypeScript checker.

These changes basically brings the JS compilation times to TS projects. So, recompilation took less than 1 second instead of 3 seconds in medium size project.

The problem with async mode is that type-errors are reported after Webpack ends up recompilation as TypeScript could be slower than Babel. PR allows to emit files compiled by Babel immediately and then wait for TS and show type errors in terminal later. Also, if there was no compilation errors and any type error occurs, we trigger a hot-reload with new errors to show error overlay in browser.

Also, I wanted to start a discussion about `skipLibCheck: false` option in default `tsconfig.json`. This makes recompilations really slow and we should consider to set it to `true` or at least give users a big warning to let them know that it could be really slow.

The following video is showing the updated workflow with a forced 2.5 second delay for type-check to give you an idea how it works.

![nov-26-2018 15-47-01](https://user-images.githubusercontent.com/5549148/49021284-9446fe80-f192-11e8-952b-8f83d77d5fbc.gif)


I'm pretty sure that PR needs some polishing and improvements but it should works as it is. Especially a "hack" with reloading the browser after type-check looks ugly to me.

cc @brunolemos as he is an initiator of an original TypeScript PR.

Should fix https://github.com/facebook/create-react-app/issues/5820

packages/react-dev-utils/WebpackDevServerUtils.js

@@ -17,22 +17,10 @@ const inquirer = require('inquirer');
 const clearConsole = require('./clearConsole');
 const formatWebpackMessages = require('./formatWebpackMessages');
 const getProcessForPort = require('./getProcessForPort');
+const typescriptFormatter = require('./typescriptFormatter');
+const forkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
 
 const isInteractive = process.stdout.isTTY;
-let handleCompile;
-
-// You can safely remove this after ejecting.
-// We only use this block for testing of Create React App itself:
-const isSmokeTest = process.argv.some(arg => arg.indexOf('--smoke-test') > -1);
-if (isSmokeTest) {
-  handleCompile = (err, stats) => {
-    if (err || stats.hasErrors() || stats.hasWarnings()) {
-      process.exit(1);
-    } else {
-      process.exit(0);
-    }
-  };
-}
 
 function prepareUrls(protocol, host, port) {
   const formatUrl = hostname =>
@@ -113,12 +101,20 @@ function printInstructions(appName, urls, useYarn) {
   console.log();
 }
 
-function createCompiler(webpack, config, appName, urls, useYarn) {
+function createCompiler(
+  webpack,
+  config,
+  appName,
+  urls,
+  useYarn,
+  useTypeScript,
+  devSocket
+) {
   // "Compiler" is a low-level interface to Webpack.
   // It lets us listen to some events and provide our own custom messages.
   let compiler;
   try {
-    compiler = webpack(config, handleCompile);
+    compiler = webpack(config);
   } catch (err) {
     console.log(chalk.red('Failed to compile.'));
     console.log();
@@ -139,10 +135,35 @@ function createCompiler(webpack, config, appName, urls, useYarn) {
   });
 
   let isFirstCompile = true;
+  let tsMessagesPromise;
+  let tsMessagesResolver;
+
+  if (useTypeScript) {
+    compiler.hooks.beforeCompile.tap('beforeCompile', () => {
+      tsMessagesPromise = new Promise(resolve => {
+        tsMessagesResolver = msgs => resolve(msgs);
+      });
+    });
+
+    forkTsCheckerWebpackPlugin
+      .getCompilerHooks(compiler)
+      .receive.tap('afterTypeScriptCheck', (diagnostics, lints) => {
+        const allMsgs = [...diagnostics, ...lints];
+        const format = message =>
+          `${message.file}\n${typescriptFormatter(message, true)}`;
+
+        tsMessagesResolver({
+          errors: allMsgs.filter(msg => msg.severity === 'error').map(format),
+          warnings: allMsgs
+            .filter(msg => msg.severity === 'warning')
+            .map(format),
+        });
+      });
+  }
 
   // "done" event fires when Webpack has finished recompiling the bundle.
   // Whether or not you have warnings or errors, you will get this event.
-  compiler.hooks.done.tap('done', stats => {
+  compiler.hooks.done.tap('done', async stats => {
     if (isInteractive) {
       clearConsole();
     }
@@ -152,9 +173,43 @@ function createCompiler(webpack, config, appName, urls, useYarn) {
     // them in a readable focused way.
     // We only construct the warnings and errors for speed:
     // https://github.com/facebook/create-react-app/issues/4492#issuecomment-421959548
-    const messages = formatWebpackMessages(
-      stats.toJson({ all: false, warnings: true, errors: true })
-    );
+    const statsData = stats.toJson({
+      all: false,
+      warnings: true,
+      errors: true,
+    });
+
+    if (useTypeScript && statsData.errors.length === 0) {
+      const delayedMsg = setTimeout(() => {
+        console.log(
+          chalk.yellow(
+            'Files successfully emitted, waiting for typecheck results...'
+          )
+        );
+      }, 100);
+
+      const messages = await tsMessagesPromise;
+      clearTimeout(delayedMsg);
+      statsData.errors.push(...messages.errors);
+      statsData.warnings.push(...messages.warnings);
+
+      // Push errors and warnings into compilation result
+      // to show them after page refresh triggered by user.
+      stats.compilation.errors.push(...messages.errors);
+      stats.compilation.warnings.push(...messages.warnings);
+
+      if (messages.errors.length > 0) {
+        devSocket.errors(messages.errors);
+      } else if (messages.warnings.length > 0) {
+        devSocket.warnings(messages.warnings);
+      }
+
+      if (isInteractive) {
+        clearConsole();
+      }
+    }
+
+    const messages = formatWebpackMessages(statsData);
     const isSuccessful = !messages.errors.length && !messages.warnings.length;
     if (isSuccessful) {
       console.log(chalk.green('Compiled successfully!'));
@@ -194,6 +249,27 @@ function createCompiler(webpack, config, appName, urls, useYarn) {
       );
     }
   });
+
+  // You can safely remove this after ejecting.
+  // We only use this block for testing of Create React App itself:
+  const isSmokeTest = process.argv.some(
+    arg => arg.indexOf('--smoke-test') > -1
+  );
+  if (isSmokeTest) {
+    compiler.hooks.failed.tap('smokeTest', async () => {
+      await tsMessagesPromise;
+      process.exit(1);
+    });
+    compiler.hooks.done.tap('smokeTest', async stats => {
+      await tsMessagesPromise;
+      if (stats.hasErrors() || stats.hasWarnings()) {
+        process.exit(1);
+      } else {
+        process.exit(0);
+      }
+    });
+  }
+
   return compiler;
 }