feat: warn if run instant prototyping in a project directory (#3508)

closes #2473

package.json

@@ -10,7 +10,7 @@
     "pretest": "yarn clean",
     "lint": "eslint --fix packages/**/*.js packages/**/bin/*",
     "check-links": "node scripts/checkLinks.js",
-    "clean": "rimraf packages/test/*",
+    "clean": "rimraf packages/test/* packages/**/temp/*",
     "sync": "node scripts/syncDeps.js",
     "boot": "node scripts/bootstrap.js",
     "release": "yarn --pure-lockfile && yarn clean && node scripts/release.js",

packages/@vue/cli-service-global/__tests__/globalService.spec.js

@@ -22,7 +22,7 @@ import App from './Other.vue'
 new Vue({ render: h => h(App) }).$mount('#app')
 `.trim()
 
-beforeAll(async () => {
+beforeEach(async () => {
   await fs.ensureDir(cwd)
   await write('App.vue', entryVue)
   await write('Other.vue', entryVue)
@@ -75,6 +75,35 @@ test('global build', async () => {
   expect(h1Text).toMatch('hi')
 })
 
+test('warn if run plain `vue build` or `vue serve` alongside a `package.json` file', async () => {
+  await write('package.json', `{
+    "name": "hello-world",
+    "version": "1.0.0",
+    "scripts": {
+      "serve": "vue-cli-service serve",
+      "build": "vue-cli-service build"
+    }
+  }`)
+
+  // Warn if a package.json with corresponding `script` field exists
+  const { stdout } = await execa(binPath, ['build'], { cwd })
+  expect(stdout).toMatch(/Did you mean .*(yarn|npm run) build/)
+
+  await fs.unlink(path.join(cwd, 'App.vue'))
+
+  // Fail if no entry file exists, also show a hint for npm scripts
+  expect(() => {
+    execa.sync(binPath, ['build'], { cwd })
+  }).toThrow(/Did you mean .*(yarn|npm run) build/)
+
+  expect(() => {
+    execa.sync(binPath, ['serve'], { cwd })
+  }).toThrow(/Did you mean .*(yarn|npm run) serve/)
+
+  // clean up, otherwise this file will affect other tests
+  await fs.unlink(path.join(cwd, 'package.json'))
+})
+
 afterAll(async () => {
   if (browser) {
     await browser.close()

packages/@vue/cli-service-global/index.js

@@ -8,9 +8,36 @@ const babelPlugin = toPlugin('@vue/cli-plugin-babel')
 const eslintPlugin = toPlugin('@vue/cli-plugin-eslint')
 const globalConfigPlugin = require('./lib/globalConfigPlugin')
 
-function resolveEntry (entry) {
-  const context = process.cwd()
+const context = process.cwd()
 
+function warnAboutNpmScript (cmd) {
+  const packageJsonPath = path.join(context, 'package.json')
+
+  if (!fs.existsSync(packageJsonPath)) {
+    return
+  }
+
+  let pkg
+  try {
+    pkg = require(packageJsonPath)
+  } catch (e) {
+    return
+  }
+
+  if (!pkg.scripts || !pkg.scripts[cmd]) {
+    return
+  }
+
+  let script = `npm run ${cmd}`
+  if (fs.existsSync(path.join(context, 'yarn.lock'))) {
+    script = `yarn ${cmd}`
+  }
+
+  console.log(`There's a ${chalk.yellow('package.json')} in the current directory.`)
+  console.log(`Did you mean ${chalk.yellow(script)}?`)
+}
+
+function resolveEntry (entry, cmd) {
   entry = entry || findExisting(context, [
     'main.js',
     'index.js',
@@ -21,14 +48,21 @@ function resolveEntry (entry) {
   if (!entry) {
     console.log(chalk.red(`Failed to locate entry file in ${chalk.yellow(context)}.`))
     console.log(chalk.red(`Valid entry file should be one of: main.js, index.js, App.vue or app.vue.`))
+
+    console.log()
+    warnAboutNpmScript(cmd)
     process.exit(1)
   }
 
   if (!fs.existsSync(path.join(context, entry))) {
     console.log(chalk.red(`Entry file ${chalk.yellow(entry)} does not exist.`))
+
+    console.log()
+    warnAboutNpmScript(cmd)
     process.exit(1)
   }
 
+  warnAboutNpmScript(cmd)
   return {
     context,
     entry
@@ -50,12 +84,12 @@ function createService (context, entry, asLib) {
 }
 
 exports.serve = (_entry, args) => {
-  const { context, entry } = resolveEntry(_entry)
+  const { context, entry } = resolveEntry(_entry, 'serve')
   createService(context, entry).run('serve', args)
 }
 
 exports.build = (_entry, args) => {
-  const { context, entry } = resolveEntry(_entry)
+  const { context, entry } = resolveEntry(_entry, 'build')
   const asLib = args.target && args.target !== 'app'
   if (asLib) {
     args.entry = entry