# NOTE: BEFORE OPENING AN ISSUE PLEASE SEE THE [README](https://github.com/babel/babel#readme). ----

Setup | Running tests | Workflow | Dependencies | Code Standards | Internals

---- # Contributing Contributions are always welcome, no matter how large or small. Before contributing, please read the [code of conduct](https://github.com/babel/babel/blob/master/CODE_OF_CONDUCT.md). ## Developing > Note: Babel moves fast. Only the latest release is guaranteed to build correctly. > Older releases are not officially supported. If you attempt to build them, do that at your own risk. #### Setup ```sh $ git clone https://github.com/babel/babel $ cd babel $ make bootstrap ``` Then you can either run: ```sh $ make build-core ``` to build Babel **once** or: ```sh $ make watch-core ``` to have Babel build itself then incrementally build files on change. #### Running tests You can run tests via: ```sh $ make test ``` This is mostly overkill and you can limit the tests to a select few by directly running them with `mocha`: ```sh $ mocha test/core/transformation.js ``` Use mocha's `--grep` option to run a subset of tests by name: ```sh $ mocha test/core/transformation.js --grep es7 ``` If you don't have `mocha` installed globally, you can still use it from Babel's dependencies in `node_modules`, but make sure `node_modules/.bin` is added to your [`$PATH`](http://unix.stackexchange.com/questions/26047/how-to-correctly-add-a-path-to-path) environment variable. #### 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 #### Dependencies + [ast-types](http://ghub.io/ast-types) This is required to monkeypatch regenerators AST definitions. Could be improved in the future. + [chalk](http://ghub.io/chalk) This is used for terminal color highlighting for syntax errors. + [convert-source-map](http://ghub.io/convert-source-map) Turns a source map object into a comment etc. + [core-js](http://ghub.io/core-js) Used for the polyfill. + [debug](http://ghub.io/debug) Used to output debugging information when NODE_DEBUG is set to babel. + [detect-indent](http://ghub.io/detect-indent) This is used in the code generator so it can infer indentation. + [estraverse](http://ghub.io/estraverse) The only method on this is attachComments. I'd like to implement our own comment attachment algorithm eventually though. + [esutils](http://ghub.io/esutils) Various ES related utilities. Check whether something is a keyword etc. + [fs-readdir-recursive](http://ghub.io/fs-readdir-recursive) Recursively search a directory for. + [globals](http://ghub.io/globals) A list of JavaScript global variables. This is used by the scope tracking to check for colliding variables. + [is-integer](http://ghub.io/is-integer) Checks if something is an integer. + [js-tokens](http://ghub.io/js-tokens) This is used to get tokens for syntax error highlighting. + [line-numbers](http://ghub.io/line-numbers) Used to produce the code frames in syntax errors. + [lodash](http://ghub.io/lodash) Used for various utilities. + [minimatch](http://ghub.io/minimatch) This is used to match glob-style ignore/only filters. + [output-file-sync](http://ghub.io/output-file-sync) Synchronously writes a file and create its ancestor directories if needed. + [path-is-absolute](http://ghub.io/path-is-absolute) Checks if a path is absolute. C:\foo and \foo are considered absolute. + [regenerator](http://ghub.io/regenerator) This is used to transform generators/async functions. + [regexpu](http://ghub.io/regexpu) Used to transform unicode regex patterns. + [repeating](http://ghub.io/repeating) Repeats a string. + [shebang-regex](http://ghub.io/shebang-regex) Literally just a regex that matches shebangs. + [slash](http://ghub.io/slash) Normalises path separators. + [source-map](http://ghub.io/source-map) Generates sourcemaps. + [source-map-support](http://ghub.io/source-map-support) Adds source map support to babel-node/babel/register. + [strip-json-comments](http://ghub.io/strip-json-comments) Remove comments from a JSON string. This is used for .babelrc files. + [to-fast-properties](http://ghub.io/to-fast-properties) A V8 trick to put an object into fast properties mode. + [trim-right](http://ghub.io/trim-right) Trims the rightside whitespace. + [path-exists](https://www.npmjs.com/package/path-exists) Checks if a path exists. (replaces the deprecated `fs.exists` methods) + [home-or-tmp](https://github.com/sindresorhus/home-or-tmp) Gets the user home directory with fallback to the system temporary directory. This is used to resolve the babel-node/babel/register cache. + [resolve](https://www.npmjs.com/package/resolve) Implements the [`require.resolve()` algorithm](http://nodejs.org/docs/v0.12.0/api/all.html#all_require_resolve) such that we can `require.resolve()` on behalf of a file asynchronously and synchronously. #### Code Standards * **General** * 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 #### Internals Please see [`/doc`](/doc) for internals documentation relevant to developing babel.