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README.md |
babel-eslint
babel-eslint allows you to lint ALL valid Babel code with the fantastic ESLint.
Why Use babel-eslint
You only need to use babel-eslint if you are using types (Flow) or experimental features not supported in ESLint itself yet. Otherwise try the default parser (you don't have to use it just because you are using Babel).
If there is an issue, first check if it can be reproduced with the regular parser or with the latest versions of
eslint
andbabel-eslint
!
For questions and support please visit the #discussion
babel slack channel (sign up here) or eslint gitter!
Note that the
ecmaFeatures
config property may still be required for ESLint to work properly with features not in ECMAScript 5 by default. Examples areglobalReturn
andmodules
).
Known Issues
Flow:
Check out eslint-plugin-flowtype: An
eslint
plugin that makes flow type annotations global variables and marks declarations as used. Solves the problem of false positives withno-undef
andno-unused-vars
.
no-undef
for global flow types:ReactElement
,ReactClass
#130- Workaround: define types as globals in
.eslintrc
or define types and import themimport type ReactElement from './types'
- Workaround: define types as globals in
no-unused-vars/no-undef
with Flow declarations (declare module A {}
) #132
Modules/strict mode
no-unused-vars: [2, {vars: local}]
#136
Please check out eslint-plugin-react for React/JSX issues
no-unused-vars
with jsx
Please check out eslint-plugin-babel for other issues
How does it work?
ESLint allows custom parsers. This is great but some of the syntax nodes that Babel supports aren't supported by ESLint. When using this plugin, ESLint is monkeypatched and your code is transformed into code that ESLint can understand. All location info such as line numbers, columns is also retained so you can track down errors with ease.
Basically babel-eslint
exports an index.js
that a linter can use.
It just needs to export a parse
method that takes in a string of code and outputs an AST.
Usage
Supported ESLint versions
ESLint | babel-eslint |
---|---|
4.x | >= 6.x |
3.x | >= 6.x |
2.x | >= 6.x |
1.x | >= 5.x |
Install
Ensure that you have substituted the correct version lock for eslint
and babel-eslint
into this command:
$ npm install eslint@4.x babel-eslint@8 --save-dev
# or
$ yarn add eslint@4.x babel-eslint@8 -D
Setup
.eslintrc
{
"parser": "babel-eslint",
"rules": {
"strict": 0
}
}
Check out the ESLint docs for all possible rules.
Configuration
sourceType
can be set to'module'
(default) or'script'
if your code isn't using ECMAScript modules.allowImportExportEverywhere
(defaultfalse
) can be set totrue
to allow import and export declarations to appear anywhere a statement is allowed if your build environment supports that. Otherwise import and export declarations can only appear at a program's top level.codeFrame
(defaulttrue
) can be set tofalse
to disable the code frame in the reporter. This is useful since some eslint formatters don't play well with it.
.eslintrc
{
"parser": "babel-eslint",
"parserOptions": {
"sourceType": "module",
"allowImportExportEverywhere": false,
"codeFrame": true
}
}
Run
$ eslint your-files-here