feat: respect existing package.json

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

@@ -1,8 +1,10 @@
+const fs = require('fs')
 const path = require('path')
 const chalk = require('chalk')
 const debug = require('debug')
 const execa = require('execa')
 const inquirer = require('inquirer')
+const readPkg = require('read-pkg')
 const semver = require('semver')
 const EventEmitter = require('events')
 const Generator = require('./Generator')
@@ -139,12 +141,7 @@ module.exports = class Creator extends EventEmitter {
       latestMinor = current
     }
     // generate package.json with plugin dependencies
-    const pkg = {
-      name,
-      version: '0.1.0',
-      private: true,
-      devDependencies: {}
-    }
+    const pkg = this.resolvePkg()
     const deps = Object.keys(preset.plugins)
     deps.forEach(dep => {
       if (preset.plugins[dep]._isPreset) {
@@ -512,6 +509,22 @@ module.exports = class Creator extends EventEmitter {
     return prompts
   }
 
+  resolvePkg () {
+    let existingPkg = {}
+    if (fs.existsSync(path.join(this.context, 'package.json'))) {
+      existingPkg = readPkg.sync({ cwd: this.context })
+    }
+    const { name, version, devDependencies, ...more } = existingPkg
+    const pkg = {
+      name: name || this.name,
+      version: version || '0.1.0',
+      private: true,
+      devDependencies: devDependencies || {},
+      ...more
+    }
+    return pkg
+  }
+
   shouldInitGit (cliOptions) {
     if (!hasGit()) {
       return false

packages/@vue/cli/package.json

@@ -50,6 +50,7 @@
     "lodash.clonedeep": "^4.5.0",
     "lru-cache": "^5.1.1",
     "minimist": "^1.2.0",
+    "read-pkg": "^5.1.1",
     "recast": "^0.18.1",
     "request": "^2.87.0",
     "request-promise-native": "^1.0.7",