refactor: make hasYarn & hasGit lazy to improve boot time

packages/@vue/cli-service/lib/commands/serve.js

@@ -97,7 +97,7 @@ module.exports = (api, options) => {
           isFirstCompile = false
 
           if (!isProduction) {
-            const buildCommand = hasYarn ? `yarn build` : `npm run build`
+            const buildCommand = hasYarn() ? `yarn build` : `npm run build`
             console.log(`  Note that the development build is not optimized.`)
             console.log(`  To create a production build, run ${chalk.cyan(buildCommand)}.`)
           } else {

packages/@vue/cli-shared-utils/lib/env.js

@@ -1,26 +1,35 @@
 const { execSync } = require('child_process')
 
+let _hasYarn
+let _hasGit
+
 // env detection
-exports.hasYarn = (() => {
+exports.hasYarn = () => {
   if (process.env.VUE_CLI_TEST) {
     return true
   }
+  if (_hasYarn != null) {
+    return _hasYarn
+  }
   try {
     execSync('yarnpkg --version', { stdio: 'ignore' })
-    return true
+    return (_hasYarn = true)
   } catch (e) {
-    return false
+    return (_hasYarn = false)
   }
-})()
+}
 
 exports.hasGit = () => {
   if (process.env.VUE_CLI_TEST) {
     return true
   }
+  if (_hasGit != null) {
+    return _hasGit
+  }
   try {
     execSync('git --version', { stdio: 'ignore' })
-    return true
+    return (_hasGit = true)
   } catch (e) {
-    return false
+    return (_hasGit = false)
   }
 }

packages/@vue/cli/lib/Creator.js

@@ -86,7 +86,7 @@ module.exports = class Creator {
     const packageManager = (
       cliOptions.packageManager ||
       loadOptions().packageManager ||
-      (hasYarn ? 'yarn' : 'npm')
+      (hasYarn() ? 'yarn' : 'npm')
     )
 
     await clearConsole()
@@ -112,7 +112,7 @@ module.exports = class Creator {
 
     // intilaize git repository before installing deps
     // so that vue-cli-service can setup git hooks.
-    if (hasGit) {
+    if (hasGit()) {
       logWithSpinner(`🗃`, `Initializing git repository...`)
       await run('git init')
     }
@@ -156,7 +156,7 @@ module.exports = class Creator {
     }
 
     // commit initial state
-    if (hasGit) {
+    if (hasGit()) {
       await run('git add -A')
       if (isTestOrDebug) {
         await run('git', ['config', 'user.name', 'test'])
@@ -179,7 +179,7 @@ module.exports = class Creator {
 
   async promptAndResolvePreset () {
     // prompt
-    await clearConsole()
+    await clearConsole(true)
     const answers = await inquirer.prompt(this.resolveFinalPrompts())
     debug('vue-cli:answers')(answers)
 
@@ -320,7 +320,7 @@ module.exports = class Creator {
 
     // ask for packageManager once
     const savedOptions = loadOptions()
-    if (hasYarn && !savedOptions.packageManager) {
+    if (!savedOptions.packageManager && hasYarn()) {
       outroPrompts.push({
         name: 'packageManager',
         type: 'list',

packages/@vue/cli/lib/invoke.js

@@ -78,7 +78,7 @@ async function invoke (pluginName, options) {
 
   if (!isTestOrDebug && depsChanged) {
     logWithSpinner('📦', `Installing additional dependencies...`)
-    const packageManager = loadOptions().packageManager || (hasYarn ? 'yarn' : 'npm')
+    const packageManager = loadOptions().packageManager || (hasYarn() ? 'yarn' : 'npm')
     await installDeps(context, packageManager)
   }
 
@@ -93,7 +93,7 @@ async function invoke (pluginName, options) {
 
   log()
   log(`   Successfully invoked generator for plugin: ${chalk.cyan(id)}`)
-  if (hasGit) {
+  if (hasGit()) {
     const { stdout } = await execa('git', ['ls-files', '--exclude-standard', '--modified', '--others'])
     log(`   The following files have been updated / added:\n`)
     log(chalk.red(stdout.split(/\r?\n/g).map(line => `     ${line}`).join('\n')))

packages/@vue/cli/lib/promptModules/linter.js

@@ -51,7 +51,7 @@ module.exports = cli => {
         value: 'save'
       },
       {
-        name: 'Lint and fix on commit' + (hasGit ? '' : chalk.red(' (requires Git)')),
+        name: 'Lint and fix on commit' + (hasGit() ? '' : chalk.red(' (requires Git)')),
         value: 'commit'
       }
     ]

packages/@vue/cli/lib/util/clearConsole.js

@@ -3,7 +3,7 @@ const semver = require('semver')
 const getVersions = require('./getVersions')
 const { clearConsole } = require('@vue/cli-shared-utils')
 
-module.exports = async function clearConsoleWithTitle () {
+module.exports = async function clearConsoleWithTitle (checkUpdate) {
   const { current, latest } = await getVersions()
 
   let title = chalk.bold.blue(`Vue CLI v${current}`)
@@ -14,7 +14,7 @@ module.exports = async function clearConsoleWithTitle () {
   if (process.env.VUE_CLI_DEBUG) {
     title += ' ' + chalk.magenta.bold('DEBUG')
   }
-  if (semver.gt(latest, current)) {
+  if (checkUpdate && semver.gt(latest, current)) {
     title += chalk.green(`
 ┌─────────────────────────${`─`.repeat(latest.length)}─┐
 │ ✨  Update available: ${latest} ✨  │

packages/@vue/cli/lib/util/loadCommand.js

@@ -12,7 +12,7 @@ module.exports = function loadCommand (commandName, moduleName) {
         if (isNotFoundError(err2)) {
           const chalk = require('chalk')
           const { hasYarn } = require('@vue/cli-shared-utils')
-          const installCommand = hasYarn ? `yarn global add` : `npm install -g`
+          const installCommand = hasYarn() ? `yarn global add` : `npm install -g`
           console.log()
           console.log(
             `  Command ${chalk.cyan(`vue ${commandName}`)} requires a global addon to be installed.\n` +