Ionic problem: [ng]Schema validation failed with the following errors:[ng]Data path".builders['app-shell']"should have required property 'class'

From the above comment session @tkerwood provide solution for this.

Updated package.json from "@angular-devkit/build-angular": "^0.800.1" to "~0.13.9"

run npm install

Everyone is focusing on downgrading @angular-devkit/build-angular version to X, or upgrading @angular/cli version to Y or latest.

However, please do not blindly try switching X or Y or latest. (Though usually, downgrading devkit should be better because upgrading CLI is a breaking change)

The correct version to choose always depends on your Angular (angular-cli) version. I've listed a few versions here.

Angular CLI v8.3.19 -> 0.803.19
Angular CLI v8.3.17 -> 0.803.17
Angular CLI v7.3.8 -> 0.13.8
Angular CLI v6-lts -> 0.8.9

For other specific versions, visit: https://github.com/angular/angular-cli/tags. It might take some digging but once you locate your CLI version, in some tags they do mention the corresponding versions for @angular-devkit/** packages.

Note: If you want to upgrade your CLI version, you should first consider upgrading to latest of your major version, do not simply jump to the next major version. *Answer used from zhuhang.jasper

Angular Cli 8 support Node Js 10.9+. I have Node.js 8, after update to 10.16 works fine.