nx/docs/shared/generators/generator-options.md

Customizing generator options

Adding a TypeScript schema

To create a TypeScript schema to use in your generator function, define a TypeScript file next to your schema.json named schema.ts. Inside the schema.ts, define an interface to match the properties in your schema.json file, and whether they are required.

export interface GeneratorOptions {
  name: string;
  type?: string;
}

Import the TypeScript schema into your generator file and replace the any in your generator function with the interface.

import { Tree, formatFiles, installPackagesTask } from '@nrwl/devkit';
import { libraryGenerator } from '@nrwl/workspace';

export default async function (tree: Tree, schema: GeneratorOptions) {
  await libraryGenerator(tree, { name: `${schema.name}-${schema.type || ''}` });
  await formatFiles(tree);
  return () => {
    installPackagesTask(tree);
  };
}

Adding static options

Static options for a generator don't prompt the user for input. To add a static option, define a key in the schema.json file with the option name, and define an object with its type, description, and optional default value.

{
  "$schema": "http://json-schema.org/schema",
  "id": "my-generator",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Library name",
      "$default": {
        "$source": "argv",
        "index": 0
      }
    },
    "type": {
      "type": "string",
      "description": "Provide the library type, such as 'data-access' or 'state'"
    }
  },
  "required": ["name"]
}

If you run the generator without providing a value for the type, it is not included in the generated name of the library.

Adding dynamic prompts

Dynamic options can prompt the user to select from a list of options. To define a prompt, add an x-prompt property to the option object, set the type to list, and define an items array for the choices.

{
  "$schema": "http://json-schema.org/schema",
  "id": "my-generator",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Library name",
      "$default": {
        "$source": "argv",
        "index": 0
      }
    },
    "type": {
      "type": "string",
      "description": "Provide the library type",
      "x-prompt": {
        "message": "Which type of library would you like to generate?",
        "type": "list",
        "items": [
          {
            "value": "data-access",
            "label": "Data Access"
          },
          {
            "value": "feature",
            "label": "Feature"
          },
          {
            "value": "state",
            "label": "State Management"
          }
        ]
      }
    }
  },
  "required": ["name"]
}

Running the generator without providing a value for the type will prompt the user to make a selection.