Hi! I'm really excited that you are interested in contributing to Vue.js. Before submitting your contribution, please make sure to take a moment and read through the following guidelines:
- [Code of Conduct](https://github.com/vuejs/vue/blob/dev/.github/CODE_OF_CONDUCT.md)
- Always use [https://new-issue.vuejs.org/](https://new-issue.vuejs.org/) to create new issues.
## Pull Request Guidelines
- Checkout a topic branch from a base branch, e.g. `master`, and merge back against that branch.
- If adding a new feature:
- Add accompanying test case.
- Provide a convincing reason to add this feature. Ideally, you should open a suggestion issue first and have it approved before working on it.
- If fixing bug:
- 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. `update entities encoding/decoding (fix #3899)`.
- Provide a detailed description of the bug in the PR. Live demo preferred.
- Add appropriate test coverage if applicable.
- It's OK to have multiple small commits as you work on the PR - GitHub can automatically squash them before merging.
- Make sure tests pass!
- Commit messages must follow the [commit message convention](./COMMIT_CONVENTION.md) so that changelogs can be automatically generated. Commit messages are automatically validated before commit.
- 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.
## Development Setup
You will need [Node.js](http://nodejs.org) **version 10+**, and [Yarn](https://yarnpkg.com/en/docs/install).
After cloning the repo, run:
``` bash
$ yarn # install the dependencies of the project
```
A high level overview of tools used:
- [TypeScript](https://www.typescriptlang.org/) as the development language
- [Rollup](https://rollupjs.org) for bundling
- [Jest](https://jestjs.io/) for unit testing
- [Prettier](https://prettier.io/) for code formatting
- [Lerna](https://github.com/lerna/lerna) for monorepo management
## Scripts
### `yarn build`
The `build` script builds all public packages (packages without `private: true` in their `package.json`).
Packages to build can be specified with fuzzy matching:
``` bash
# build runtime-core only
yarn build runtime-core
# build all packages matching "runtime"
yarn build runtime
```
By default, each package will be built in multiple distribution formats as specified in the `buildOptions.formats` field in its `package.json`. These can be overwritten via the `-f` flag. The following formats are supported:
- **`global`**: for direct use via `<script>` in the browser. The global variable exposed is specified via the `buildOptions.name` field in a package's `package.json`.
- **`esm`**: for use with bundlers.
- **`esm-browser`**: for in-browser usage via native ES modules import (`<scripttype="module">`)
- **`cjs`**: for use in Node.js via `require()`.
For example, to build `runtime-core` with the global build only:
``` bash
yarn build runtime-core -f global
```
Multiple formats can be specified as a comma-separated list:
``` bash
yarn build runtime-core -f esm,cjs
```
### `yarn dev`
The `dev` script bundles a target package (default: `vue`) in a specified format (default: `global`) in dev mode and watches for changes. This is useful when you want to load up a build in an HTML page for quick debugging:
- The `dev` script also supports fuzzy match for the target package, but will only match the first package matched.
- The `dev` script supports specifying build format via the `-f` flag just like the `build` script.
### `yarn test`
The `yarn test` script simply calls the `jest` binary, so all [Jest CLI Options](https://jestjs.io/docs/en/cli) can be used. Some examples:
``` bash
# run all tests
$ yarn test
# run tests in watch mode
$ yarn test --watch
# run all tests under the runtime-core package
$ yarn test runtime-core
# run tests in a specific file
$ yarn test fileName
# run a specific test in a specific file
$ yarn test fileName -t 'test name'
```
## Project Structure
This project uses a [monorepo](https://github.com/lerna/lerna#about) structure and contains the following packages:
-`reactivity`: The reactivity system. It can be used standalone as a framework-agnostic package.
-`runtime-core`: The platform-agnostic runtime core. Includes code for the virtual dom renderer, component implementation and JavaScript APIs. Higher-order runtimes (i.e. custom renderers) targeting specific platforms can be created using this package.
-`runtime-dom`: The runtime targeting the browser. Includes handling of native DOM API, attributes, properties, event handlers etc.
-`runtime-test`: The lightweight runtime for testing. Can be used in any JavaScript environment since it "renders" a tree of plain JavaScript objects. The tree can be used to assert correct render output. Also provides utilities for serializing the tree, triggering events, and recording actual node operations performed during an update.
-`server-renderer`: Package for server-side rendering.
-`compiler-core`: The platform-agnostic compiler core. Includes the extensible base of the compiler and all platform-agnostic plugins.
-`compiler-dom`: Compiler with additional plugins specifically targeting the browser.
-`shared`: **Private.** Platform-agnostic internal utilities shared across multiple packages. This package is private and not published.
-`vue`: The public facing "full build" which includes both the runtime AND the compiler.
Note that when importing these packages, the `@vue/` prefix is needed:
``` js
import { h } from '@vue/runtime-core'
```
## Contributing Tests
Unit tests are collocated with the code being tested in each package, inside directories named `__tests__`. Consult the [Jest docs](https://jestjs.io/docs/en/using-matchers) and existing test cases for how to write new test specs. Here are some additional guidelines:
- Use the minimal API needed for a test case. For example, if a test can be written without involving the reactivity system or a component, it should be written so. This limits the test's exposure to changes in unrelated parts and makes it more stable.
- If testing platform agnostic behavior or asserting low-level virtual DOM operations, use `@vue/runtime-test`.
- Only use platform-specific runtimes if the test is asserting platform-specific behavior.
## Financial Contribution
As a pure community-driven project without major corporate backing, we also welcome financial contributions via Patreon and OpenCollective.
- [Become a backer or sponsor on Patreon](https://www.patreon.com/evanyou)
- [Become a backer or sponsor on OpenCollective](https://opencollective.com/vuejs)
### What's the difference between Patreon and OpenCollective funding?
Funds donated via Patreon go directly to support Evan You's full-time work on Vue.js. Funds donated via OpenCollective are managed with transparent expenses and will be used for compensating work and expenses for core team members or sponsoring community events. Your name/logo will receive proper recognition and exposure by donating on either platform.
## Credits
Thank you to all the people who have already contributed to Vue.js!
