"ValidationError: webpack Dev Server Invalid Options" error when running a newly created project.

Version

3.7.0

Reproduction link

[http://It is not possible to provide a reproduction link in this case.](http://It is not possible to provide a reproduction link in this case.)

Environment info

  System:
    OS: macOS High Sierra 10.13.6
    CPU: (8) x64 Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz
  Binaries:
    Node: 8.15.1 - /usr/local/opt/node@8/bin/node
    Yarn: 1.15.2 - /usr/local/bin/yarn
    npm: 6.4.1 - /usr/local/opt/node@8/bin/npm
  Browsers:
    Chrome: 74.0.3729.157
    Firefox: 66.0.3
    Safari: 11.1.2
  npmPackages:
    @vue/babel-helper-vue-jsx-merge-props:  1.0.0
    @vue/babel-plugin-transform-vue-jsx:  1.0.0
    @vue/babel-preset-app:  3.7.0
    @vue/babel-preset-jsx:  1.0.0
    @vue/babel-sugar-functional-vue:  1.0.0
    @vue/babel-sugar-inject-h:  1.0.0
    @vue/babel-sugar-v-model:  1.0.0
    @vue/babel-sugar-v-on:  1.0.0
    @vue/cli-overlay:  3.7.0
    @vue/cli-plugin-babel: ^3.7.0 => 3.7.0
    @vue/cli-plugin-eslint: ^3.7.0 => 3.7.0
    @vue/cli-service: ^3.7.0 => 3.7.0
    @vue/cli-shared-utils:  3.7.0
    @vue/component-compiler-utils:  2.6.0
    @vue/eslint-config-airbnb: ^4.0.0 => 4.0.0
    @vue/preload-webpack-plugin:  1.1.0
    @vue/web-component-wrapper:  1.2.0
    eslint-plugin-vue: ^5.0.0 => 5.2.2 (4.7.1)
    vue: ^2.6.10 => 2.6.10
    vue-eslint-parser:  5.0.0 (2.0.3)
    vue-hot-reload-api:  2.3.3
    vue-loader:  15.7.0
    vue-style-loader:  4.1.2
    vue-template-compiler: ^2.5.21 => 2.6.10
    vue-template-es2015-compiler:  1.9.1
  npmGlobalPackages:
    @vue/cli: Not Found

Steps to reproduce

1. Create a new project with vue-cli
2. Go to the project dir
3. Run yarn serve

What is expected?

Webpack web server starts

What is actually happening?

Ther’s an error in the console

→ yarn serve
yarn run v1.15.2
$ vue-cli-service serve
 INFO  Starting development server...
 ERROR  ValidationError: webpack Dev Server Invalid Options

options.clientLogLevel should be {String} and equal to one of the allowed values

 [ 'info', 'warn', 'error', 'debug', 'trace', 'silent' ]

 (https://webpack.js.org/configuration/dev-server/#devserverclientloglevel)

ValidationError: webpack Dev Server Invalid Options

options.clientLogLevel should be {String} and equal to one of the allowed values

 [ 'info', 'warn', 'error', 'debug', 'trace', 'silent' ]

 (https://webpack.js.org/configuration/dev-server/#devserverclientloglevel)

    at validateOptions (/Users/wube/htdocs/tic-tac-toe/node_modules/schema-utils/src/validateOptions.js:32:11)
    at new Server (/Users/wube/htdocs/tic-tac-toe/node_modules/webpack-dev-server/lib/Server.js:71:5)
    at serve (/Users/wube/htdocs/tic-tac-toe/node_modules/@vue/cli-service/lib/commands/serve.js:138:20)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:189:7)
    at Function.Module.runMain (module.js:696:11)
    at startup (bootstrap_node.js:204:16)
    at bootstrap_node.js:625:3
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

---

The build command works fine, the problem is related to webpack dev server.

[dland512]

Getting this as well. This was working fine as little as 9 or 10 hours ago. The problem appears to be related to the autogenerated webpack config file (node_modules/@vue/cli-service/lib/commands/serve.js), which contains this:

const server = new WebpackDevServer(compiler, Object.assign({
      clientLogLevel: 'none',

As the error states, 'none' is no longer a valid option for some reason (not sure what changed to cause that). It can be worked around by adding a vue.config.js file to the root of the project that contains this:

module.exports = {
    devServer: {
        clientLogLevel: 'info'
    }
};

[LinusBorg]

Closin this in favor of #4016