ng: schema with key or id “http://json-schema.org/draft-06/schema” already exists

Question

When I tried adding the Material library to my angular project by running npm install --save @angular/material @angular/cdk , I ran into the problems described in this question: Error TS2315: Type 'ElementRef' is not generic material angular

So following the advice there, I ran npm install -g @angular/cli@latest ; now, all ng commands yield the following:

$ ng Unknown error: Error: schema with key or id "http://json-schema.org/draft-06/schema" already exists

ng works from other folders, so I guess something is now broken within the project. How can this be fixed?

Searching for this error message didn't yield anything useful and the project's json files (like tsconfig.json) all look fine.

package.json:

{
  "name": "some-frontend",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build --prod",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "6.0.1",
    "@angular/cdk": "^6.0.1",
    "@angular/common": "6.0.1",
    "@angular/compiler": "6.0.1",
    "@angular/core": "6.0.1",
    "@angular/forms": "6.0.1",
    "@angular/http": "6.0.1",
    "@angular/material": "^6.0.1",
    "@angular/platform-browser": "6.0.1",
    "@angular/platform-browser-dynamic": "6.0.1",
    "@angular/router": "6.0.1",
    "core-js": "^2.4.1",
    "npm": "^6.0.1",
    "rxjs": "^6.1.0",
    "zone.js": "^0.8.26"
  },
  "devDependencies": {
    "@angular/cli": "6.0.1",
    "@angular/compiler-cli": "6.0.1",
    "@angular/language-service": "6.0.1",
    "@types/jasmine": "~2.8.3",
    "@types/jasminewd2": "~2.0.2",
    "@types/node": "~6.0.60",
    "codelyzer": "^4.0.1",
    "jasmine-core": "~2.8.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~2.0.0",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.2",
    "ts-node": "~4.1.0",
    "tslint": "~5.9.1",
    "typescript": "2.7.2"
  }
}

Previous package.json file:

{
  "name": "some-frontend",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build --prod",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^5.2.0",
    "@angular/common": "^5.2.0",
    "@angular/compiler": "^5.2.0",
    "@angular/core": "^5.2.0",
    "@angular/forms": "^5.2.0",
    "@angular/http": "^5.2.0",
    "@angular/platform-browser": "^5.2.0",
    "@angular/platform-browser-dynamic": "^5.2.0",
    "@angular/router": "^5.2.0",
    "core-js": "^2.4.1",
    "rxjs": "^5.5.6",
    "zone.js": "^0.8.19"
  },
  "devDependencies": {
    "@angular/cli": "~1.7.4",
    "@angular/compiler-cli": "^5.2.0",
    "@angular/language-service": "^5.2.0",
    "@types/jasmine": "~2.8.3",
    "@types/jasminewd2": "~2.0.2",
    "@types/node": "~6.0.60",
    "codelyzer": "^4.0.1",
    "jasmine-core": "~2.8.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~2.0.0",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.2",
    "ts-node": "~4.1.0",
    "tslint": "~5.9.1",
    "typescript": "~2.5.3"
  }
}

Answer 1

It seems that this was caused by packages which haven't been installed completely/wrong. Running

npm install --save

caused npm to complain about broken files; after removing those, the installation completed successfully.

Then however ng complained about the file angular.json being missing; this can be fixed by migrating properly, as described in a related question :

ng update @angular/cli --migrate-only --from=1.7.4

Answer 2

rm -rf /node_modules

and after that installing the packages again by

npm install

worked for me.