Error: Schema validation failed with the following errors: Data path “” should NOT have additional properties(project)

Question

After migrating application from angular 5 to 6, on running ng serve the following errors pop up.

Schema validation failed with the following errors:

Answer 1

When upgrading Angular from version 10 to 8 I got very similar error, namely Schema validation failed with the following errors: Data path "" should NOT have additional properties(serverTarget)..

The solution was remove all "serverTarget" references from below "serve". The below was wrong:

"serve": {
  "builder": "@angular-devkit/build-angular:dev-server",
  "options": {
    "browserTarget": "my_app:build"
    "serverTarget": "my_app:server"
  },
  "configurations": {
    "production": {
      "browserTarget": "my_app:build:production",
      "serverTarget": "my_app:server:production"
    }
  }
},

The below is correct and compiled successfully:

"serve": {
  "builder": "@angular-devkit/build-angular:dev-server",
  "options": {
    "browserTarget": "my_app:build"
  },
  "configurations": {
    "production": {
      "browserTarget": "my_app:build:production"
    }
  }
},

Bonus for those who are working with Angular Universal. If you want to run SSR on localhost, then indeed you need the serverTarget. However, for that you have to create a new section within the angular.json, something like:

"serve-ssr": {
  "builder": "@nguniversal/builders:ssr-dev-server",
  "options": {
    "browserTarget": "my_app:build",
    "serverTarget": "my_app:server"
  },
  "configurations": {
    "production": {
      "browserTarget": "my_app:build:production",
      "serverTarget": "my_app:server:production"
    }
  }
},

Then ng run my_app:serve-ssr.

Actually I got this error when upgrading Angular from version 10 into 8 and wanted to improve some things. Then I've messed up the serverTarget thing with that wrong thinking, hopefully this will help out someone with Angular Universal in a project.