fix: should fallback to local eslint, fixes instant prototyping

closes #2866

packages/@vue/cli-plugin-eslint/index.js

@@ -6,7 +6,9 @@ module.exports = (api, options) => {
     // Use loadModule to allow users to customize their ESLint dependency version.
     const { loadModule } = require('@vue/cli-shared-utils')
     const cwd = api.getCwd()
-    const eslintPkg = loadModule('eslint/package.json', cwd, true)
+    const eslintPkg =
+      loadModule('eslint/package.json', cwd, true) ||
+      require('eslint/package.json')
 
     // eslint-loader doesn't bust cache when eslint config changes
     // so we have to manually generate a cache identifier that takes the config
@@ -46,7 +48,9 @@ module.exports = (api, options) => {
               cacheIdentifier,
               emitWarning: options.lintOnSave !== 'error',
               emitError: options.lintOnSave === 'error',
-              formatter: loadModule('eslint/lib/formatters/codeframe', cwd, true)
+              formatter:
+                loadModule('eslint/lib/formatters/codeframe', cwd, true) ||
+                require('eslint/lib/formatters/codeframe')
             })
     })
   }

packages/@vue/cli-plugin-eslint/lint.js

@@ -21,7 +21,7 @@ module.exports = function lint (args = {}, api) {
   const path = require('path')
   const cwd = api.resolve('.')
   const { log, done, exit, chalk, loadModule } = require('@vue/cli-shared-utils')
-  const { CLIEngine } = loadModule('eslint', cwd, true)
+  const { CLIEngine } = loadModule('eslint', cwd, true) || require('eslint')
   const extensions = require('./eslintOptions').extensions(api)
 
   const argsConfig = normalizeConfig(args)

packages/@vue/cli-service-global/package.json

@@ -27,7 +27,6 @@
     "@vue/cli-service": "^3.1.0",
     "babel-eslint": "^10.0.1",
     "chalk": "^2.4.1",
-    "eslint": "^5.8.0",
     "eslint-plugin-vue": "^5.0.0-0",
     "resolve": "^1.8.1",
     "vue": "^2.5.17",