CLIAPI

add-on

Community add-ons are currently experimental. The API may change. Don't use them in production yet!

This guide covers how to create, test, and publish community add-ons for sv.

Quick start

The easiest way to create an add-on is using the addon template:

npx sv create --template addon my-addon
cd my-addon

Add-on structure

Typically, an add-on looks like this:

hover keywords in the code to have some more context

import { import transformstransforms, import sveltesvelte } from '@sveltejs/sv-utils';
import { import defineAddondefineAddon, import defineAddonOptionsdefineAddonOptions } from 'sv';

// Define options that will be prompted to the user (or passed as arguments)
const const options: anyoptions = import defineAddonOptionsdefineAddonOptions()
	.add('who', {
		question: stringquestion: 'To whom should the addon say hello?',
		type: stringtype: 'string' // boolean | number | select | multiselect
	})
	.build();

// your add-on definition, the entry point
export default import defineAddondefineAddon({
	id: stringid: 'your-addon-name',
	// shortDescription: 'does X',   // optional: one-liner shown in prompts
	// homepage: 'https://...',      // optional: link to docs/repo

	options: anyoptions,

	// preparing step, check requirements and dependencies
	setup: ({ dependsOn }: {
    dependsOn: any;
}) => voidsetup: ({ dependsOn: anydependsOn }) => {
		dependsOn: anydependsOn('tailwindcss');
	},

	// actual execution of the addon
	run: ({ isKit, cancel, sv, options, directory }: {
    isKit: any;
    cancel: any;
    sv: any;
    options: any;
    directory: any;
}) => anyrun: ({ isKit: anyisKit, cancel: anycancel, sv: anysv, options: anyoptions, directory: anydirectory }) => {
		if (!isKit: anyisKit) return cancel: anycancel('SvelteKit is required');

		// Add "Hello [who]!" to the root page
		sv: anysv.file(
			directory: anydirectory.routes + '/+page.svelte',
			import transformstransforms.svelte((ast: anyast) => {
				import sveltesvelte.addFragment(ast: anyast, `<p>Hello ${options: anyoptions.who}!</p>`);
			})
		);
	}
});

sv owns the file system — sv.file() resolves the path, reads the file, applies the transform, and writes the result. @sveltejs/sv-utils owns the content — transforms.svelte() handles parsing, gives you the AST, and serializes back. See sv-utils for the full API.

Development with file: protocol

While developing your add-on, you can test it locally using the file: protocol:

# In your test project
npx sv add file:../path/to/my-addon

This allows you to iterate quickly without publishing to npm.

Testing with sv/testing

The sv/testing module provides utilities for testing your add-on:

import { import setupTestsetupTest } from 'sv/testing';
import { const test: TestAPIDefines a test case with a given name and test function. The test function can optionally be configured with test options.
@param
name - The name of the test or a function that will be used as a test name.
@param
optionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@param
optionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throws
Error If called inside another test function.
@example
// Define a simple test
test('should add two numbers', () => {
  expect(add(1, 2)).toBe(3);
});
@example
// Define a test with options
test('should subtract two numbers', { retry: 3 }, () => {
  expect(subtract(5, 2)).toBe(3);
});test, const expect: ExpectStaticexpect } from 'vitest';
import import addonaddon from './index.js';

test<object>(name: string | Function, fn?: TestFunction<object> | undefined, options?: number): void (+1 overload)Defines a test case with a given name and test function. The test function can optionally be configured with test options.
@param
name - The name of the test or a function that will be used as a test name.
@param
optionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@param
optionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throws
Error If called inside another test function.
@example
// Define a simple test
test('should add two numbers', () => {
  expect(add(1, 2)).toBe(3);
});
@example
// Define a test with options
test('should subtract two numbers', { retry: 3 }, () => {
  expect(subtract(5, 2)).toBe(3);
});test('adds hello message', async () => {
	const { const content: anycontent } = await import setupTestsetupTest({
		addon: anyaddon,
		options: {
    who: string;
}options: { who: stringwho: 'World' },
		files: {
    'src/routes/+page.svelte': string;
}files: {
			'src/routes/+page.svelte': '<h1>Welcome</h1>'
		}
	});

	expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(const content: anycontent('src/routes/+page.svelte')).JestAssertion<any>.toContain: <string>(item: string) => voidUsed when you want to check that an item is in a list.
For testing the items in the list, this uses ===, a strict equality check.
@example
expect(items).toContain('apple');
expect(numbers).toContain(5);
toContain('Hello World!');
});

Building and publishing

Bundling

Community add-ons are bundled with tsdown into a single file. Everything is bundled except sv (peer dependency, provided at runtime).

npm run build

Package structure

Your add-on must have sv as a peer dependency and no dependencies in package.json:

{
	"name": "@your-org/sv",
	"version": "1.0.0",
	"type": "module",
	"exports": {
		".": "./src/index.js"
	},
	"publishConfig": {
		"access": "public",
		"exports": {
			".": { "default": "./dist/index.js" }
		}
	},
	"peerDependencies": {
		"sv": "^0.13.0"
	},
	"keywords": ["sv-add"]
}

exports points to ./src/index.js for local development with the file: protocol.
publishConfig.exports overrides exports when publishing, pointing to the bundled ./dist/index.js.

Add the sv-add keyword so users can discover your add-on on npm.

Export options

Your package can export the add-on in two ways:

Default export (recommended for dedicated add-on packages):
```
{
	"exports": {
		".": "./src/index.js"
	}
}
```

/sv export (for packages that have other functionality):

{
	"exports": {
		".": "./src/main.js",
		"./sv": "./src/addon.js"
	}
}

Publishing

Community add-ons must be scoped packages (e.g. @your-org/sv). Users install with npx sv add @your-org.

npm login
npm publish

prepublishOnly automatically runs the build before publishing.

Next steps

You can optionally display guidance after your add-on runs:

export default defineAddon({
	// ...
	nextSteps: ({ options }: {
    options: any;
}) => string[]nextSteps: ({ options }) => [
		`Run ${color.command('npm run dev')} to start developing`,
		`Check out the docs at https://...`
	]
});

Version compatibility

Your add-on should specify the minimum sv version it requires in peerDependencies. If a user's sv version has a different major version than what your add-on was built for, they will see a compatibility warning.

Edit this page on GitHub llms.txt

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