# Local Generators

Local plugin generators provide a way to automate many tasks you regularly perform as part of your development workflow. Whether it is scaffolding out components, features, or ensuring libraries are generated and structured in a certain way, generators help you standardize these tasks in a consistent, and predictable manner.

Nx provides tooling around creating, and running custom generators from within your workspace. This guide shows you how to create, run, and customize generators within your Nx workspace.

{% youtube
src="https://www.youtube.com/embed/ubgroK5T6cA"
title="Create a Nx Generator in 100 seconds"
width="100%" /%}

## Creating a generator

If you don't already have a local plugin, use Nx to generate one:

```shell
# replace `latest` with the version that matches your Nx version
npm install @nrwl/nx-plugin@latest
nx g @nrwl/nx-plugin:plugin my-plugin
```

Use the Nx CLI to generate the initial files needed for your generator.

```shell
nx generate @nrwl/nx-plugin:generator my-generator --project=my-plugin
```

After the command is finished, the generator is created in the plugin `generators` folder.

```text
happynrwl/
├── apps/
├── libs/
│   ├── my-plugin
│   │   ├── src
│   │   │   ├── generators
│   │   │   |   └── my-generator/
│   │   │   |   |    ├── generator.spec.ts
│   │   │   |   |    ├── generator.ts
│   │   │   |   |    ├── schema.d.ts
│   │   │   |   |    └── schema.json
├── nx.json
├── package.json
└── tsconfig.base.json
```

The `generator.ts` provides an entry point to the generator. The file contains a function that is called to perform manipulations on a tree that represents the file system.
The `schema.json` provides a description of the generator, available options, validation information, and default values.

The initial generator function creates a library.

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

export default async function (tree: Tree, schema: any) {
  await libraryGenerator(tree, { name: schema.name });
  await formatFiles(tree);
  return () => {
    installPackagesTask(tree);
  };
}
```

To invoke other generators, import the entry point function and run it against the tree. `async/await` can be used to make code with Promises read like procedural code. The generator function may return a callback function that is executed after changes to the file system have been applied.

In the `schema.json` file for your generator, the `name` is provided as a default option. The `cli` property is set to `nx` to signal that this is a generator that uses `@nrwl/devkit` and not `@angular-devkit`.

```json {% fileName="schema.json" %}
{
  "cli": "nx",
  "id": "test",
  "type": "object",
  "properties": {
    "name": {
      "type": "string",
      "description": "Library name",
      "$default": {
        "$source": "argv",
        "index": 0
      }
    }
  },
  "required": ["name"]
}
```

The `$default` object is used to read arguments from the command-line that are passed to the generator. The first argument passed to this schematic is used as the `name` property.

## Running a generator

To run a generator, invoke the `nx generate` command with the name of the generator.

```shell
nx generate @myorg/my-plugin:my-generator mylib
```

## Debugging generators

### With Visual Studio Code

1. Open the Command Palette and choose `Debug: Create JavaScript Debug Terminal`.
   This will open a terminal with debugging enabled.
2. Set breakpoints in your code
3. Run `nx g my-generator` in the debug terminal.

![vscode-schematics-debug](/shared/images/nx-console/vscode-schematics-debug.png)

## Generator Utilities

The [`@nrwl/devkit` package](/packages/devkit/documents/index) provides many utility functions that can be used in generators to help with modifying files, reading and updating configuration files, and working with an Abstract Syntax Tree (AST).
