throw new Error('invalid "instanceof" keyword value ' + c);

[john1jan]

Getting this error while running
webpack-dev-server --config ./webpack.client.js --hot

• Operating System: Mac OS High Sierra
• Node Version: 9.9.0
• NPM Version: 5.7.1
• webpack Version: 4.1.1
• webpack-dev-server Version:3.1.1
  Full stacktrace

node_modules/webpack/node_modules/ajv-keywords/keywords/instanceof.js:52
    throw new Error('invalid "instanceof" keyword value ' + c);
    ^

Error: invalid "instanceof" keyword value Promise
    at getConstructor (node_modules/webpack/node_modules/ajv-keywords/keywords/instanceof.js:52:11)
    at Ajv.compile (node_modules/webpack/node_modules/ajv-keywords/keywords/instanceof.js:21:27)
    at Object.useCustomRule (node_modules/webpack/node_modules/ajv/lib/compile/index.js:275:26)
    at Object.generate_custom [as code] (node_modules/webpack/node_modules/ajv/lib/dotjs/custom.js:32:24)
    at Object.generate_validate [as validate] (node_modules/webpack/node_modules/ajv/lib/dotjs/validate.js:347:35)
    at Object.generate_anyOf [as code] (node_modules/webpack/node_modules/ajv/lib/dotjs/anyOf.js:34:27)
    at generate_validate (node_modules/webpack/node_modules/ajv/lib/dotjs/validate.js:347:35)
    at localCompile (node_modules/webpack/node_modules/ajv/lib/compile/index.js:87:22)
    at Ajv.compile (node_modules/webpack/node_modules/ajv/lib/compile/index.js:56:13)
    at Ajv._compile (node_modules/webpack/node_modules/ajv/lib/ajv.js:358:27)
    at Ajv.compile (node_modules/webpack/node_modules/ajv/lib/ajv.js:118:37)
    at validateObject (node_modules/webpack/lib/validateSchema.js:36:23)
    at validateSchema (node_modules/webpack/lib/validateSchema.js:31:10)
    at processConfiguredOptions (node_modules/webpack-cli/bin/convert-argv.js:156:48)
    at module.exports (node_modules/webpack-cli/bin/convert-argv.js:150:10)
    at Object.<anonymous> (node_modules/webpack-dev-server/bin/webpack-dev-server.js:234:54)

[silky]

why do bad things happen to good people?

we manually hacked our package.json to use webpack 4.2.0 and this error goes away!

woo!

[DCbryant]

I solved by lowerring my webpack-dev-server version,The problem is there

[ndabAP]

@DCbryant which version do you use now?

[DCbryant]

@ndabAP 2.9.1

[styks1987]

I had a similar issue but it was due to not having webpack-cli installed locally.

[rohan-paul]

Had this issue today, and went away, after upgrading webpack to 4.5.0 and also installing webpack-cli locally..

[zvs001]

npm i webpack@latest -g helps me

[MgSam]

So this happened because webpack pushed breaking changes in a minor version and most people probably have their package.json file with a carrot or tilde in front of the webpack dependencies. Removing that carrot or tilde to freeze to the version specified and running npm install fixed the problem for me.

I think it's extremely irresponsible for webpack to have made these breaking changes in a minor version. The webpack CLI separation should have only occurred in a major release. You have literally millions of people depending on this package, please put some more thought into release numbers.

[kopax]

I have this error in a lerna project when I try to install in two different package it then fail to find the module webpack-cli:

$ ./node_modules/.bin/webpack-dev-server --progress --color --hot --watch --mode development
The CLI moved into a separate package: webpack-cli.
Please install 'webpack-cli' in addition to webpack itself to use the CLI.
-> When using npm: npm install webpack-cli -D
-> When using yarn: yarn add webpack-cli -D
module.js:559
    throw err;
    ^

Error: Cannot find module 'webpack-cli/bin/config-yargs'
    at Function.Module._resolveFilename (module.js:557:15)
    at Function.Module._load (module.js:484:25)
    at Module.require (module.js:606:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/webpack-dev-server/bin/webpack-dev-server.js:65:1)
    at Module._compile (module.js:662:30)
    at Object.Module._extensions..js (module.js:673:10)
    at Module.load (module.js:575:32)
    at tryModuleLoad (module.js:515:12)
    at Function.Module._load (module.js:507:3)
error An unexpected error occurred: "Command failed.

so I moved it to the top package.json, and then I have this error:

yarn run v1.5.1
$ ./node_modules/.bin/webpack-dev-server --progress --color --hot --watch --mode development
/home/dka/workspace/github.com/yeutech/react-admin/node_modules/webpack/node_modules/ajv-keywords/keywords/instanceof.js:52
    throw new Error('invalid "instanceof" keyword value ' + c);
    ^

Error: invalid "instanceof" keyword value Promise
    at getConstructor (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/webpack/node_modules/ajv-keywords/keywords/instanceof.js:52:11)
    at Ajv.compile (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/webpack/node_modules/ajv-keywords/keywords/instanceof.js:21:27)
    at Object.useCustomRule (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/compile/index.js:275:26)
    at Object.generate_custom [as code] (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/dotjs/custom.js:32:24)
    at Object.generate_validate [as validate] (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/dotjs/validate.js:347:35)
    at Object.generate_anyOf [as code] (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/dotjs/anyOf.js:34:27)
    at generate_validate (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/dotjs/validate.js:347:35)
    at localCompile (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/compile/index.js:87:22)
    at Ajv.compile (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/compile/index.js:56:13)
    at Ajv._compile (/home/dka/workspace/github.com/yeutech/react-admin/node_modules/ajv/lib/ajv.js:358:27)
error An unexpected error occurred: "Command failed.
Exit code: 1

I have tried to downgrade webpack from 4.5.0 to 4.2.0 as @silky recommend but that doesn't help.

Any idea on how to solve this?

[GQM-dong]

maybe you can change your package.json
update the webpack to 4.X
delete your node_modules
npm install again
and then it's work

[BrandonDickson]

@kopax, I was able to solve this by updating lerna to 2.10.0 from 2.0.0-rc5, and updating webpack in all my package.json files. I believe the problem stemmed from the fact that I was updating webpack one project at a time, and I was hoisting the modules with lerna, but the updates resolved it.

[SpaceK33z]

It looks like this issue is related to webpack and/or webpack-cli, not webpack-dev-server, so I'm closing this. If you believe this is an issue in WDS please provide a test repository, because I cannot reproduce this.

[HamidOsouli-zz]

remember to lower your webpack-dev-server globaly not localy use :
npm install webpack-dev-server@2.9.1 -g --save-dev and after that you are set

[kunwang0916]

npm install webpack-dev-server@2.x, works for me.

[realgs]

I read this topic for a second time within 2 weeks so I decided to write down my own suggestions in case I will come back anytime in the future;) The below is a complete list of dependencies I had to upgrade to upgrade from vulnerable react-dom@16.0.0 to @16.0.1:

❯ yarn add react@16.0.1 react-dom@16.0.1 webpack-dev-server@3.1.14 live-server@1.2.1 extract-text-webpack-plugin@next
❯ yarn add -D webpack-cli

remove node_modules
npm install
add --mode development to your CLI command (webpack-dev-server --mode development)
try again to start the project with yarn run dev-server (or whatever is your script to run the project locally)

[AbuAmeeer]

you can use npm run build instead of

[imzubair10]

following worked for me
npm install webpack-dev-server@2.11.0 --save-dev

[rramiachraf]

following worked for me
npm install webpack-dev-server@2.11.0 --save-dev

Thank you, this is actually worked..