Hi! I’m really excited that you are interested in contributing to Vue.js. Before submitting your contribution though, please make sure to take a moment and read through the following guidelines.
- The issue list of this repo is **exclusively** for bug reports and feature requests. Non-conforming issues will be closed immediately.
- For simple beginner questions, you can get quick answers from [The Gitter chat room](https://gitter.im/vuejs/vue).
- For more complicated questions, you can use [the official forum](http://forum.vuejs.org/) or StackOverflow. Make sure to provide enough information when asking your questions - this makes it easier for others to help you!
- Try to search for your issue, it may have already been answered or even fixed in the development branch.
- Check if the issue is reproducible with the latest stable version of Vue. If you are using a pre-release, please indicate the specific version you are using.
- It is **required** that you clearly describe the steps necessary to reproduce the issue you are running into. Issues with no clear repro steps will not be triaged. If an issue labeled "need repro" receives no further input from the issue author for more than 5 days, it will be closed.
- It is recommended that you make a JSFiddle/JSBin/Codepen to demonstrate your issue. You could start with [this template](http://jsfiddle.net/5sH6A/) that already includes the latest version of Vue.
- For bugs that involves build setups, you can create a reproduction repository with steps in the README.
- If your issue is resolved but still open, don’t hesitate to close it. In case you found a solution by yourself, it could be helpful to explain how you fixed it.
## Pull Request Guidelines
- The `master` branch is basically just a snapshot of the latest stable release. All development should be done in dedicated branches. **Do not submit PRs against the `master` branch.**
- Checkout a topic branch from the relevant branch, e.g. `dev`, and merge back against that branch.
- Work in the `src` folder and **DO NOT** checkin `dist` in the commits.
- It's OK to have multiple small commits as you work on the PR - we will let GitHub automatically squash it before merging.
- Make sure `npm test` passes. (see [development setup](#development-setup))
- If adding new feature:
- Add accompanying test case.
- Provide convincing reason to add this feature. Ideally you should open a suggestion issue first and have it greenlighted before working on it.
- If fixing a bug:
- Provide detailed description of the bug in the PR. Live demo preferred.
- Add appropriate test coverage if applicable.
## Development Setup
You will need [Node.js](http://nodejs.org) and [Java Runtime Environment](http://www.oracle.com/technetwork/java/javase/downloads/index.html) (needed for running Selenium server during e2e tests).
After cloning the repo, run:
``` bash
$ npm install
```
### Commonly used NPM scripts
``` bash
# watch and auto re-build dist/vue.js
$ npm run dev
# watch and auto re-run unit tests in Chrome
$ npm run dev:test
# build all dist files, including npm packages
$ npm run build
# run the full test suite, include linting / type checking
$ npm test
```
There are some other scripts available in the `scripts` section of the `package.json` file.
The default test script will do the following: lint with ESLint -> type check with Flow -> unit tests with coverage -> e2e tests. **Please make sure to have this pass successfully before submitting a PR.** Although the same tests will be run against your PR on the CI server, it is better to have it working locally beforehand.
## Project Structure
- **`build`**: contains build-related configuration files. In most cases you don't need to touch them.
- **`dist`**: contains built files for distribution. Note this directory is only updated when a release happens; they do not reflect the latest changes in development branches.
- **`flow`**: contains type declarations for [Flow](https://flowtype.org/). These declarations are loaded **globally** and you will see them used in type annotations in normal source code.
- **`packages`**: contains `vue-server-renderer` and `vue-template-compiler`, which are distributed as separate NPM packages. They are automatically generated from the source code and always have the same version with the main `vue` package.
- **`test`**: contains all tests. The unit tests are written with [Jasmine](http://jasmine.github.io/2.3/introduction.html) and run with [Karma](http://karma-runner.github.io/0.13/index.html). The e2e tests are written for and run with [Nightwatch.js](http://nightwatchjs.org/).
- **`src`**: contains the source code, obviously. The codebase is written in ES2015 with [Flow](https://flowtype.org/) type annotations.
- **`entries`**: contains entries for different builds and packages.
- **`web-runtime`**: the entry for `dist/vue.common.js`, a.k.a the runtime-only build. It does not include the template to render function compiler, so it does not support the `template` option. **This is set as the `main` field in `package.json` so it is the default export when you import Vue as an NPM package.**
- **`web-runtime-with-compiler`**: the entry for `dist/vue.js`, a.k.a the standalone build. It includes the template to render function compiler. To use this build from the NPM packages, do `import Vue from 'vue/dist/vue'`, or alias `vue` to `vue/dist/vue` in your build tool configuration.
- **`web-compiler.js`**: the entry for the `vue-template-compiler` NPM package.
- **`web-server-renderer.js`**: the entry for the `vue-server-renderer` NPM package.
- **`compiler`**: contains code for the template-to-render-function compiler.
The compiler consists of a parser (converts template strings to element ASTs), an optimizer (detects static trees for vdom render optimization), and a code generator (generate render function code from element ASTs). Note the codegen directly generates code strings from the element AST - it's done this way for smaller code size because the compiler is shipped to the browser in the standalone build.
The Vue 2.0 core is platform-agnostic - which means code inside `core` should be able to run in any JavaScript environment, be it the browser, Node.js, or an embedded JavaScript runtime in native applications.
- **`observer`**: contains code related to the reactivity system.
Each platform module contains three parts: `compiler`, `runtime` and `server`, corresponding to the three directories above. Each part contains platform-specific modules/utilities which are then imported and injected to the core counterparts in platform-specific entry files. For example, the code implementing the logic behind `v-bind:class` is in `platforms/web/runtime/modules/class.js` - which is imported in `entries/web-runtime.js` and used to create the browser-specific vdom patching function.
- **`sfc`**: contains single-file component (`*.vue` files) parsing logic. This is used in the `vue-template-compiler` package.
- **`shared`**: contains utilities shared across the entire codebase.
