109 lines
2.8 KiB
Markdown
109 lines
2.8 KiB
Markdown
# Contributing
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Contributions are always welcome, no matter how large or small. Before
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contributing, please read the
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[code of conduct](https://github.com/babel/babel/blob/master/CODE_OF_CONDUCT.md).
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## Setup local env
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> Install yarn beforehand: https://yarnpkg.com/en/docs/install
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To start developing on Babylon you only need to install its dependencies:
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```bash
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git clone https://github.com/babel/babylon
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cd babylon
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yarn
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```
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## Tests
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### Running tests locally
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To run a build, tests and perform lint/flow checks:
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```bash
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yarn test
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```
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If you only want to run the tests:
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```bash
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yarn run test-only
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```
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Note, this does not actually run a build, so you may have to call `yarn run build` after
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performing any changes.
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### Running one test
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To run only a single test, add `"only": true` to the `options.json` inside any test fixture folder (you may have to create the file if it doesn't exist).
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For example, let's say we want to only run the test for the [`test/fixtures/comments/basic/shebang-import`](https://github.com/babel/babylon/tree/7.0/test/fixtures/comments/basic/shebang-import) fixture.
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Add `"only": true` to its `options.json`:
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```json
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{
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"sourceType": "module",
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"only": true
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}
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```
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Then, run the tests using the same command as before:
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```bash
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yarn run test-only
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```
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### Checking code coverage locally
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To generate code coverage, be sure to set `BABEL_ENV=test` so that code is instrumented during
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the rollup build.
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```bash
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BABEL_ENV=test yarn run build && yarn run test-coverage
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```
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### Writing tests
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Writing tests for Babylon is very
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[similar to Babel](https://github.com/babel/babel/blob/master/CONTRIBUTING.md#writing-tests).
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Inside the `tests/fixtures` folder are categories/groupings of test fixtures (es2015, flow,
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etc.). To add a test, create a folder under one of these groupings (or create a new one) with a
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descriptive name, and add the following:
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* Create an `actual.js` file that contains the code you want Babylon to parse.
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* Add an `expected.json` file with the expected parser output. For added convenience, if
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there is no `expected.json` present, the test runner will generate one for you.
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## Cross repository changes
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If you are making changes to Babylon which make it necessary to also change things in Babel
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you will want to link both repositories together. This can be done by doing the following
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(assuming you have both Babel and Babylon already checked out):
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```bash
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cd babylon/
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yarn link
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yarn run build
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cd ../babel/
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make bootstrap
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yarn link babylon
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cd packages/babel-core/
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yarn link babylon
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cd ../babel-template/
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yarn link babylon
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cd ../babel-traverse/
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yarn link babylon
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cd ../babel-generator/
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yarn link babylon
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cd ../babel-types/
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yarn link babylon
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cd ../..
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make build
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make test
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```
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From now on Babel will use your local checkout of Babylon for its tests.
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