Hi! We're really excited that you're interested in contributing to Vite! Before submitting your contribution, please read through the following guide. We also suggest you read the [Project Philosophy](https://vitejs.dev/guide/philosophy) in our documentation.
You can use [StackBlitz Codeflow](https://stackblitz.com/codeflow) to fix bugs or implement features. You'll see a Codeflow button on issues to start a PR to fix them. A button will also appear on PRs to review them without needing to check out the branch locally. When using Codeflow, the Vite repository will be cloned for you in an online editor, with the Vite package built in watch mode ready to test your changes. If you'd like to learn more, check out the [Codeflow docs](https://developer.stackblitz.com/codeflow/what-is-codeflow).
[](https://pr.new/vitejs/vite)
To develop locally, fork the Vite repository and clone it in your local machine. The Vite repo is a monorepo using pnpm workspaces. The package manager used to install and link dependencies must be [pnpm](https://pnpm.io/).
You can alternatively use [Vite.js Docker Dev](https://github.com/nystudio107/vitejs-docker-dev) for a containerized Docker setup for Vite.js development.
> Vite uses pnpm v7. If you are working on multiple projects with different versions of pnpm, it's recommended to enable [Corepack](https://github.com/nodejs/corepack) by running `corepack enable`.
To use breakpoints and explore code execution, you can use the ["Run and Debug"](https://code.visualstudio.com/docs/editor/debugging) feature from VS Code.
2. Click the "Run and Debug" icon in the activity bar of the editor, which opens the [_Run and Debug view_](https://code.visualstudio.com/docs/editor/debugging#_run-and-debug-view).
5. The execution will stop at the `debugger` statement, and you can use the [Debug toolbar](https://code.visualstudio.com/docs/editor/debugging#_debug-actions) to continue, step over, and restart the process...
Some errors are masked and hidden away because of the layers of abstraction and sandboxed nature added by Vitest, Playwright, and Chromium. In order to see what's actually going wrong and the contents of the devtools console in those instances, follow this setup:
1. Add a `debugger` statement to the `playground/vitestSetup.ts` -> `afterAll` hook. This will pause execution before the tests quit and the Playwright browser instance exits.
4. In the sources panel in the right column, click the play button to resume execution, and allow the tests to run, which will open a Chromium instance.
You may wish to test your locally modified copy of Vite against another package that is built with Vite. For pnpm, after building Vite, you can use [`pnpm.overrides`](https://pnpm.io/package_json#pnpmoverrides) to do this. Note that `pnpm.overrides` must be specified in the root `package.json`, and you must list the package as a dependency in the root `package.json`:
Each package under `playground/` contains a `__tests__` directory. The tests are run using [Vitest](https://vitest.dev/) + [Playwright](https://playwright.dev/) with custom integrations to make writing tests simple. The detailed setup is inside `vitest.config.e2e.js` and `playground/vitest*` files.
Some playgrounds define variants to run the same app using different config setups. By convention, when running a test spec file in a nested folder in `__tests__`, the setup will try to use a config file named `vite.config-{folderName}.js` at the playground's root. You can see an example of variants in the [assets playground](https://github.com/vitejs/vite/tree/main/playground/assets).
Before running the tests, make sure that [Vite has been built](#repo-setup). On Windows, you may want to [activate Developer Mode](https://docs.microsoft.com/en-us/windows/apps/get-started/enable-your-device-for-development) to resolve [issues with symlink creation for non-admins](https://github.com/vitejs/vite/issues/7390). Also, you may want to [set git `core.symlinks` to `true` to resolve issues with symlinks in git](https://github.com/vitejs/vite/issues/5242).
-`pnpm run test-serve [match]` or `pnpm run test-build [match]` runs tests in specific packages that match the given filter. e.g. `pnpm run test-serve asset` runs tests for both `playground/asset` and `vite/src/node/__tests__/asset` under serve mode.
Other than tests under `playground/` for integration tests, packages might contain unit tests under their `__tests__` directory. Unit tests are powered by [Vitest](https://vitest.dev/). The detailed config is inside `vitest.config.ts` files.
Inside playground tests, you can import the `page` object from `~utils`, which is a Playwright [`Page`](https://playwright.dev/docs/api/class-page) instance that has already navigated to the served page of the current playground. So, writing a test is as simple as:
Some common test helpers (e.g. `testDir`, `isBuild`, or `editFile`) are also available in the utils. Source code is located at `playground/test-utils.ts`.
Note: The test build environment uses a [different default set of Vite config](https://github.com/vitejs/vite/blob/main/playground/vitestSetup.ts#L102-L122) to skip transpilation during tests to make it faster. This may produce a different result compared to the default production build.
To add new tests, you should find a related playground to the fix or feature (or create a new one). As an example, static assets loading is tested in the [assets playground](https://github.com/vitejs/vite/tree/main/playground/assets). In this Vite app, there is a test for `?raw` imports with [a section defined in the `index.html` for it](https://github.com/vitejs/vite/blob/main/playground/assets/index.html#L121):
In the [spec tests](https://github.com/vitejs/vite/blob/main/playground/assets/__tests__/assets.spec.ts#L180), the modifications to the DOM listed above are used to test this feature:
In many test cases, we need to mock dependencies using `link:` and `file:` protocols. `pnpm` treats `link:` as symlinks and `file:` as hardlinks. To test dependencies as if they were copied into `node_modules`, use the `file:` protocol. Otherwise, use the `link:` protocol.
You can set the `DEBUG` environment variable to turn on debugging logs (e.g. `DEBUG="vite:resolve"`). To see all debug logs, you can set `DEBUG="vite:*"`, but be warned that it will be quite noisy. You can run `grep -r "createDebugger('vite:" packages/vite/src/` to see a list of available debug scopes.
- If you are resolving a special issue, add `(fix #xxxx[,#xxxx])` (#xxxx is the issue id) in your PR title for a better release log (e.g. `fix: update entities encoding/decoding (fix #3899)`).
- No need to worry about code style as long as you have installed the dev dependencies. Modified files are automatically formatted with Prettier on commit (by invoking [Git Hooks](https://git-scm.com/docs/githooks) via [simple-git-hooks](https://github.com/toplenboren/simple-git-hooks)).
> The following section is mostly for maintainers who have commit access, but it's helpful to go through if you intend to make non-trivial contributions to the codebase.
We use Rollup to pre-bundle most dependencies before publishing! Therefore, most dependencies, even those used in runtime source code, should be added under `devDependencies` by default. This also creates the following constraints that we need to be aware of in the codebase.
In some cases, we intentionally lazy-require some dependencies to improve start-up performance. However, note that we cannot use simple `require('somedep')` calls since these are ignored in ESM files, so the dependency won't be included in the bundle, and the actual dependency won't even be there when published since they are in `devDependencies`.
Avoid deps with large transitive dependencies that result in bloated size compared to the functionality it provides. For example, `http-proxy` itself plus `@types/http-proxy` is a little over 1MB in size, but `http-proxy-middleware` pulls in a ton of dependencies that make it 7MB(!) when a minimal custom middleware on top of `http-proxy` only requires a couple of lines of code.
Vite aims to be fully usable as a dependency in a TypeScript project (e.g. it should provide proper typings for VitePress), and also in `vite.config.ts`. This means technically a dependency whose types are exposed needs to be part of `dependencies` instead of `devDependencies`. However, this also means we won't be able to bundle it.
To get around this, we inline some of these dependencies' types in `packages/vite/src/types`. This way, we can still expose the typing but bundle the dependency's source code.
For types shared between client and node, they should be added into `packages/vite/types`. These types are not bundled and are published as is (though they are still considered internal). Dependency types within this directory (e.g. `packages/vite/types/chokidar.d.ts`) are deprecated and should be added to `packages/vite/src/types` instead.
We already have many config options, and we should avoid fixing an issue by adding yet another one. Before adding an option, consider whether the problem:
