"ng serve" command shows unhandled exception error

Question

Given below is the error message that I recieve

An unhandled exception occurred: Cannot find module '@angular-devkit/build-angular/package.json'
Require stack:
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\architect\node\node-modules-architect-host.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\architect\node\index.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\models\architect-command.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\commands\serve-impl.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\schematics\tools\export-ref.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\node_modules\@angular-devkit\schematics\tools\index.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\utilities\json-schema.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\models\command-runner.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\lib\cli\index.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\lib\init.js
- C:\Users\user\AppData\Roaming\npm\node_modules\@angular\cli\bin\ng
See "C:\Users\user\AppData\Local\Temp\ng-MDn3so\angular-errors.log" for further details.​

What is the reason for this error ?
My angular CLI version is 12 and the angular core version is 10. I tried updating angular core but it is not being updated

Answer 1

A simple fix for this could be these steps.

1. remove node_modules rm -rf node_modules or just delete them
2. run npm i or npm i --only=dev(only when all modules are already installed just need to save the dev dependencies)
3. run ng serve or npm start

If the above steps show same error then you should update your dependencies.

1. run npm update
2. run npm i @angular-devkit/build-angular or npm install --save-dev @angular-devkit/build-angular