Vue CLI ValidationError: webpack Dev Server Invalid Options

This morning I ran into an issue creating a new Vue project using the Vue CLI. The strange thing about this is that I just created a new project yesterday and it ran fine. I did some digging around and this seems to be affecting a lot of users so I figured I would throw together a quick post about.

Creating & Running a new VueJS Project

I started out my morning by creating a new project using the Vue CLI. After I created the project I changed into that directory and typed the command npm run serve which calls vue-cli-service serve. A few seconds after trying to startup I received the following error in the terminal.

 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/vega/dev/vue/hello-vue-cli/node_modules/schema-utils/src/validateOptions.js:32:11)
    at new Server (/Users/vega/dev/vue/hello-vue-cli/node_modules/webpack-dev-server/lib/Server.js:71:5)
    at serve (/Users/vega/dev/vue/hello-vue-cli/node_modules/@vue/cli-service/lib/commands/serve.js:138:20)
    at process._tickCallback (internal/process/next_tick.js:68:7)
    at Function.Module.runMain (internal/modules/cjs/loader.js:745:11)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:743:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! hello-vue-cli@0.1.0 serve: `vue-cli-service serve`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the hello-vue-cli@0.1.0 serve script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/vega/.npm/_logs/2019-05-17T15_05_54_552Z-debug.log

I checked the version of the Vue CLI by running the command vue -V and I was running the latest 3.7.0. I thought maybe I did something wrong so removed the project by running rm -Rf hello-vue-cli and tried again only to run into the same error.

I next wondered if this was affecting all of my projects or just new ones. I went into an existing project I had and ran npm run serve and it started up just fine. This was adding to my head scratching because I didn't update NodeJS, NPM or Vue this morning so what the heck was going on.

Vue CLI Issues on Github

At this point, I was pretty confused so my next step was to head over to Github and see if anyone else was seeing similar issues. Sure enough, the first 2 posts looked very similar to what I was experiencing.

Shout out to dland512 for providing some clarity as to what was happening. It appears that the problem is with the generated webpack configuration node_modules/@vue/cli-service/lib/commands/serve.js which has the following:

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

If you look back at the original error it said:

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' ]

Still not sure what has caused this but it could be the vue-cli-service itself. The workaround is to create a new file in the root of your project vue.config.js that contains the following:

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

After adding this configuration I was able to run the project with no errors. If you want to read more about the Vue CLI global configuration you can check out the documentation here.

Conclusion

I am guessing by the time this article gets indexed it will no longer be an issue but I thought it was important to write up. This is one of those errors that would have completely derailed a day or even a week for me 15 years ago. With experience and a lot of patience, I have learned how to deal with issues like this that will ultimately come up. I hope this article either fixed this issue for you or just gave you some insight into my thought process of working through a frustrating issue. As always ...

Happy Coding
Dan