Contributing

Contributions are always welcome, no matter how large or small. Before contributing, please read the code of conduct.

NOTE: Please do not send pull requests that fix linting issues. It's highly likely that they've already been fixed by the time it's submitted and it just pollutes the git tree.

Developing

Setup

$ git clone https://github.com/babel/babel
$ cd babel
$ make bootstrap

Then you need to run:

$ make watch-core

This will compile babel and then sit in the background and on file modification recompile the necessary files.

Running tests

You can run tests via:

$ make test

This will usually take around two minutes as it's compiling the entire test262 test suite and validating it's AST. This is mostly overkill and you can limit the tests to a select few by directly running them with mocha:

$ mocha test/transformation.js

Linting

Please follow the correct code style, this ensures that the code is consistent and increases maintainability.

$ make lint

Workflow

Fork the repository
Clone your fork and change directory to it (git clone git@github.com:yourUserName/babel.git && cd babel)
Install the project dependencies (make bootstrap)
Link your forked clone (npm link)
Develop your changes ensuring you're fetching updates from upstream often
Ensure the test are passing (make test)
Create new pull request explaining your proposed change or reference an issue in your commit message

Code Standards

General
- No ES6 syntax features or methods, exclusively ES5.
- Max of five arguments for functions
- Max depth of four nested blocks
- 2-spaced soft tabs
Naming
- CamelCase all class names
- camelBack all variable names
Spacing
- Spaces after all keywords
- Spaces before all left curly braces
Comments
- Use JSDoc-style comments for methods
- Single-line comments for ambiguous code
Quotes
- Always use double quotes
- Only use single quotes when the string contains a double quote
Declaration
- No unused variables
- No pollution of global variables and prototypes

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