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New: group-exports rule
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‎CHANGELOG.md

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@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
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This change log adheres to standards from [Keep a CHANGELOG](http://keepachangelog.com).
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## [Unreleased]
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### Added
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- Add [`group-exports`] rule: style-guide rule to report use of multiple named exports ([#721], thanks [@Alaneor])
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### Changed
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- [`no-extraneous-dependencies`]: use `read-pkg-up` to simplify finding + loading `package.json` ([#680], thanks [@wtgtybhertgeghgtwtg])
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[`no-webpack-loader-syntax`]: ./docs/rules/no-webpack-loader-syntax.md
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[`no-unassigned-import`]: ./docs/rules/no-unassigned-import.md
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[`unambiguous`]: ./docs/rules/unambiguous.md
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[`group-exports`]: ./docs/rules/group-exports.md
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[#721]: https://github.com/benmosher/eslint-plugin-import/pull/721
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[#680]: https://github.com/benmosher/eslint-plugin-import/pull/680
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[#654]: https://github.com/benmosher/eslint-plugin-import/pull/654
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[#639]: https://github.com/benmosher/eslint-plugin-import/pull/639
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[@ntdb]: https://github.com/ntdb
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[@jakubsta]: https://github.com/jakubsta
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[@wtgtybhertgeghgtwtg]: https://github.com/wtgtybhertgeghgtwtg
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[@Alaneor]: https://github.com/Alaneor

‎README.md

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@@ -76,6 +76,7 @@ This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, a
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* Limit the maximum number of dependencies a module can have ([`max-dependencies`])
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* Forbid unassigned imports ([`no-unassigned-import`])
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* Forbid named default exports ([`no-named-default`])
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* Prefer single named export declaration ([`group-exports`])
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[`first`]: ./docs/rules/first.md
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[`no-duplicates`]: ./docs/rules/no-duplicates.md
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[`max-dependencies`]: ./docs/rules/max-dependencies.md
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[`no-unassigned-import`]: ./docs/rules/no-unassigned-import.md
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[`no-named-default`]: ./docs/rules/no-named-default.md
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[`group-exports`]: ./docs/rules/group-exports.md
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## Installation
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‎docs/rules/group-exports.md

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# group-exports
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Reports when multiple named exports or CommonJS assignments are present in a single file and when the default export is not adjacent to the named export.
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**Rationale:** An `export` declaration or `module.exports` assignment can appear anywhere in the code. By requiring a single export declaration along with the default export being placed next to the named export, your exports will remain at one place, making it easier to see what exports a module provides.
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## Rule Details
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This rule warns whenever a single file contains multiple named exports or assignments to `module.exports` (or `exports`) and when the default export is not adjacent to the named export.
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### Valid
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```js
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// Default export is adjacent to named export -> ok
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export default function test() {}
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// A single named export -> ok
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export const valid = true
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```
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```js
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const first = true
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const second = true
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// A single named export -> ok
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export {
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first,
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second,
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}
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```
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```js
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// A single exports assignment -> ok
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module.exports = {
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first: true,
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second: true
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}
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```
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### Invalid
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```js
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// Multiple named exports -> not ok!
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export const first = true
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export const second = true
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```
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```js
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// Default export is not adjacent to the named export -> not ok!
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export default {}
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const first = true
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export { first }
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```
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```js
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// Multiple exports assignments -> not ok!
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exports.first = true
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exports.second = true
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```
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## When Not To Use It
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If you do not mind having your exports spread across the file, you can safely turn this rule off.

‎src/index.js

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@@ -9,6 +9,7 @@ export const rules = {
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'extensions': require('./rules/extensions'),
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'no-restricted-paths': require('./rules/no-restricted-paths'),
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'no-internal-modules': require('./rules/no-internal-modules'),
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'group-exports': require('./rules/group-exports'),
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'no-named-default': require('./rules/no-named-default'),
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'no-named-as-default': require('./rules/no-named-as-default'),

‎src/rules/group-exports.js

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const meta = {}
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const errors = {
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ExportNamedDeclaration:
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'Multiple named export declarations; consolidate all named exports into a single statement',
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ExportDefaultDeclaration:
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'Default export declaration should be adjacent to named export',
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MemberExpression:
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'Multiple CommonJS exports; consolidate all exports into a single assignment to ' +
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'`module.exports`',
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}
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/**
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* Check if two nodes are adjacent (only whitespace between them)
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*
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* The two nodes do not have to be sorted in the order they appear in the code.
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*
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* @param {Object} opts Options for the check
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* @param {Object} opts.context The context of the nodes
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* @param {Object} opts.first The first node
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* @param {Object} opts.second The second node
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* @return {Boolean}
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* @private
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*/
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function isAdjacent(opts = {}) {
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const sourceCode = opts.context.getSourceCode()
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if (sourceCode.getTokensBetween(opts.first, opts.second).length ||
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sourceCode.getTokensBetween(opts.second, opts.first).length) {
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return false
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}
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return true
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}
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/**
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* Determine how many property accesses precede this node
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*
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* For example, `module.exports` = 1, `module.exports.something` = 2 and so on.
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*
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* @param {Object} node The node being visited
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* @return {Number}
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* @private
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*/
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function accessorDepth(node) {
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let depth = 0
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while (node.type === 'MemberExpression') {
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depth++
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node = node.parent
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}
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return depth
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}
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function create(context) {
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const exports = {
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named: new Set(),
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default: null,
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last: null,
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}
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return {
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ExportDefaultDeclaration(node) {
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exports.default = node
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},
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ExportNamedDeclaration(node) {
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exports.named.add(node)
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exports.last = node
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},
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MemberExpression(node) {
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if (['MemberExpression', 'AssignmentExpression'].indexOf(node.parent.type) === -1) {
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return
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}
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// Member expressions on the right side of the assignment do not interest us
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if (node.parent.type === 'AssignmentExpression' && node.parent.left !== node) {
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return
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}
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if (node.object.name === 'module' && node.property.name === 'exports') {
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// module.exports.exported.*: assignments this deep should not be considered as exports
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if (accessorDepth(node) > 2) {
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return
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}
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return void exports.named.add(node)
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}
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if (node.object.name === 'exports') {
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// exports.exported.*: assignments this deep should not be considered as exports
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if (accessorDepth(node) > 1) {
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return
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}
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return void exports.named.add(node)
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}
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},
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'Program:exit': function onExit() {
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if (exports.named.size > 1) {
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for (const node of exports.named) {
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context.report({
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node,
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message: errors[node.type],
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})
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}
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}
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// There is exactly one named export and a default export -> check if they are adjacent
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if (exports.default && exports.last && exports.named.size === 1) {
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const adjacent = isAdjacent({
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context,
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first: exports.default,
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second: exports.last,
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})
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if (!adjacent) {
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context.report({
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node: exports.default,
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message: errors[exports.default.type],
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})
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}
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}
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},
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}
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}
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export default {
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meta,
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create,
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}

‎tests/src/rules/group-exports.js

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import { test } from '../utils'
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import { RuleTester } from 'eslint'
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import rule from 'rules/group-exports'
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const errors = {
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named:
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'Multiple named export declarations; consolidate all named exports into a single statement',
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default:
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'Default export declaration should be adjacent to named export',
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commonjs:
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'Multiple CommonJS exports; consolidate all exports into a single assignment to ' +
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'`module.exports`',
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}
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const ruleTester = new RuleTester()
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ruleTester.run('group-exports', rule, {
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valid: [
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test({ code: 'export const test = true' }),
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test({ code: 'export default {}\nexport const test = true' }),
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test({ code: [
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'const first = true',
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'const second = true',
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'export { first,\nsecond }',
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].join('\n') }),
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test({ code: 'export default {}\n/* test */\nexport const test = true'}),
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test({ code: 'export default {}\n// test\nexport const test = true'}),
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test({ code: 'export const test = true\n/* test */\nexport default {}'}),
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test({ code: 'export const test = true\n// test\nexport default {}'}),
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test({ code: 'module.exports = {} '}),
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test({ code: 'module.exports = { test: true,\nanother: false }' }),
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test({ code: 'exports.test = true' }),
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test({ code: 'module.exports = {}\nconst test = module.exports' }),
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test({ code: 'exports.test = true\nconst test = exports.test' }),
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test({ code: 'module.exports = {}\nmodule.exports.too.deep = true' }),
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test({ code: 'module.exports = {}\nexports.too.deep = true' }),
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],
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invalid: [
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test({
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code: [
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'export const test = true',
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'export const another = true',
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].join('\n'),
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errors: [
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errors.named,
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errors.named,
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],
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}),
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test({
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code: [
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'module.exports = {}',
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'module.exports.test = true',
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'module.exports.another = true',
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].join('\n'),
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errors: [
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errors.commonjs,
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errors.commonjs,
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errors.commonjs,
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],
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}),
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test({
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code: [
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'module.exports = {}',
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'module.exports = {}',
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].join('\n'),
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errors: [
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errors.commonjs,
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errors.commonjs,
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],
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}),
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test({
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code: 'export default {}\nconst test = true\nexport { test }',
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errors: [errors.default],
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}),
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test({
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code: 'const test = true\nexport { test }\nconst another = true\nexport default {}',
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errors: [errors.default],
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}),
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],
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})

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