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 `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 you are resolving a special issue, add `(fix #xxxx[,#xxx])` (#xxxx is the issue id) in your PR title for a better release log, e.g. `update entities encoding/decoding (fix #3899)`.
You will need [Node.js](http://nodejs.org) **version 6+** and [Java Runtime Environment](http://www.oracle.com/technetwork/java/javase/downloads/index.html) (needed for running Selenium server during e2e tests).
# 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.
- **`build`**: contains build-related configuration files. In most cases you don't need to touch them. However, it would be helpful to familiarize yourself with the following files:
-`build/alias.js`: module import aliases used across all source code and tests.
-`build/config.js`: contains the build configurations for all files found in `dist/`. Check this file if you want to find out the entry source file for a dist file.
- **`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.
- **`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.
