eslint-plugin-import

This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, and prevent issues with misspelling of file paths and import names. All the goodness that the ES2015+ static module syntax intends to provide, marked up in your editor.

IF YOU ARE USING THIS WITH SUBLIME: see the bottom section for important info.

Rules

• Ensure imports point to a file/module that can be resolved. (no-unresolved)
• Ensure named imports correspond to a named export in the remote file. (named)
• Ensure a default export is present, given a default import. (default)
• Ensure imported namespaces contain dereferenced properties as they are dereferenced. (namespace)
• Report any invalid exports, i.e. re-export of the same name (export)

Helpful warnings:

• Report use of exported name as identifier of default export (no-named-as-default)

Style guide:

• Report CommonJS require calls and module.exports or exports.*. (no-commonjs)
• Report AMD require and define calls. (no-amd)
• Ensure all imports appear before other statements (imports-first)
• Report repeated import of the same module in multiple places (no-duplicates)

Installation

npm install eslint-plugin-import -g

or if you manage ESLint as a dev dependency:

# inside your project's working tree
npm install eslint-plugin-import --save-dev

As of v0.9, all rules are off by default. However, you may configure them manually in your .eslintrc, or extend one of the canned base configs from the eslint-config-import package:

---
extends:
  - "eslint:recommended"
  - import/warnings  # after `npm i -D eslint-config-import`-ing

# or configure manually:
plugins:
  - import

rules:
  import/no-unresolved: [2, {commonjs: true, amd: true}]
  import/named: 2
  import/namespace: 2
  import/default: 2
  import/export: 2
  # etc...

Resolver plugins

With the advent of module bundlers and the current state of modules and module syntax specs, it's not always obvious where import x from 'module' should look to find the file behind module.

Up through v0.10ish, this plugin has directly used substack's resolve plugin, which implements Node's import behavior. This works pretty well in most cases.

However, Webpack allows a number of things in import module source strings that Node does not, such as loaders (import 'file!./whatever') and a number of aliasing schemes, such as externals: mapping a module id to a global name at runtime (allowing some modules to be included more traditionally via script tags).

In the interest of supporting both of these, v0.11 introduces resolver plugins. At the moment, these are modules exporting a single function:

exports.resolveImport = function (source, file, config) {
  // return source's absolute path given
  // - file: absolute path of importing module
  // - config: optional config provided for this resolver

  // return `null` if source is a "core" module (i.e. "fs", "crypto") that
  // can't be found on the filesystem
}

The default node plugin that uses resolve is a handful of lines:

var resolve = require('resolve')
  , path = require('path')
  , assign = require('object-assign')

exports.resolveImport = function resolveImport(source, file, config) {
  if (resolve.isCore(source)) return null

  return resolve.sync(source, opts(path.dirname(file), config))
}

function opts(basedir, config) {
  return assign( {}
               , config
               , { basedir: basedir }
               )
}

It essentially just uses the current file to get a reference base directory (basedir) and then passes through any explicit config from the .eslintrc; things like non-standard file extensions, module directories, etc.

Currently Node and Webpack resolution have been implemented, but the resolvers are just npm packages, so third party packages are supported (and encouraged!).

Just install a resolver as eslint-import-resolver-foo and reference it as such:

settings:
  import/resolver: foo

or with a config object:

settings:
  import/resolver:
    foo: { someConfigKey: value }

Settings

You may set the following settings in your .eslintrc:

import/ignore

A list of regex strings that, if matched by a path, will not report the matching module if no exports are found. In practice, this means rules other than no-unresolved will not report on any imports with (absolute) paths matching this pattern, unless exports were found when parsing. This allows you to ignore node_modules but still properly lint packages that define a jsnext:main in package.json (Redux, D3's v4 packages, etc.).

Note: setting this explicitly will replace the default of node_modules, so you may need to include it in your own list if you still want to ignore it. Example:

settings:
  import/ignore:
    - node_modules       # mostly CommonJS (ignored by default)
    - \.coffee$          # fraught with parse errors
    - \.(scss|less|css)$ # can't parse unprocessed CSS modules, either

import/resolver

See resolver plugins.

import/parser

This setting allows you to provide a custom parser module, in the event your project uses syntax not understood by Babel.

This plugin defaults to using Babylon, Babel's internal parser, but is also compatible with Espree's AST. As long as the import nodes follow ESTree, any parser should work.

If you're using babel-eslint as ESLint's parser, and especially if you are using any ES7+ features (object spread, decorators, etc.) you should specify it here, as well:

settings:
  import/parser: babel-eslint

If you're using the shared config eslint-config-import, you can also check out import/es7-jsx, which enables JSX and all current Babylon ES7 features.

I am hoping to obviate this setting (and import/parse-options) entirely via a pull request whereby I can just use whatever parser is configured for ESLint proper. Coming to you whenever ESLint 2.0 is released. 😎

import/parse-options

This setting will be merged 1-level deep (think Object.assign) with the default parse options and passed as the second parameter to the parser: parse(file, options). See the import/es7-jsx config file for an example of explicit parse options for Babylon.

Or, if you are using another parser, you may want to set these options as well. (and maybe contribute another config file! i.e. eslint-config-import/espree)

Here is an example .eslintrc for reference:

extends:
  - "eslint:recommended"
  - import/warnings  # optionally start from eslint-config-import

# if not using the `extends` package, make sure to add the plugin here:
plugins:
  - import

rules:
  import/default: 2
  import/no-unresolved: 1

settings:

  import/ignore:
    # any imported module path matching one of these patterns will not be parsed
    - 'node_modules' # this is the default, but must be included if overwritten
    - '\\.es5$'

  import/resolver: webpack # will use 'node' if not specified

  import/parser: esprima-fb  # default is 'babylon'. change if needed.

SublimeLinter-eslint

SublimeLinter-eslint introduced a change to support .eslintignore files which altered the way file paths are passed to ESLint when linting during editing. This change sends a relative path instead of the absolute path to the file (as ESLint normally provides), which can make it impossible for this plugin to resolve dependencies on the filesystem.

This workaround should no longer be necessary with the release of ESLint 2.0, when .eslintignore will be updated to work more like a .gitignore, which should support proper ignoring of absolute paths via --stdin-filename.

In the meantime, see roadhump/SublimeLinter-eslint#58 for more details and discussion, but essentially, you may find you need to add the following SublimeLinter config to your Sublime project file:

{
    "folders":
    [
        {
            "path": "code"
        }
    ],
    "SublimeLinter":
    {
        "linters":
        {
            "eslint":
            {
                "chdir": "${project}/code"
            }
        }
    }
}

Note that ${project}/code matches the code provided at folders[0].path.

The purpose of the chdir setting, in this case, is to set the working directory from which ESLint is executed to be the same as the directory on which SublimeLinter-eslint bases the relative path it provides.

See the SublimeLinter docs on chdir for more information, in case this does not work with your project.

If you are not using .eslintignore, or don't have a Sublime project file, you can also do the following via a .sublimelinterrc file in some ancestor directory of your code:

{
  "linters": {
    "eslint": {
      "args": ["--stdin-filename", "@"]
    }
  }
}

I also found that I needed to set rc_search_limit to null, which removes the file hierarchy search limit when looking up the directory tree for .sublimelinterrc:

In Package Settings / SublimeLinter / User Settings:

{
  "user": {
    "rc_search_limit": null
  }
}

I believe this defaults to 3, so you may not need to alter it depending on your project folder max depth.