[New] group-exports: make aggregate module exports valid

Author: Attila Bartha

CHANGELOG.md

@@ -5,6 +5,9 @@ This change log adheres to standards from [Keep a CHANGELOG](http://keepachangel
 
 ## [Unreleased]
 
+### Added
+- [`group-exports`]: make aggregate module exports valid ([#1472], thanks [@atikenny])
+
 ### Added
 - support `parseForESLint` from custom parser ([#1435], thanks [@JounQin])
 
@@ -604,6 +607,7 @@ for info on changes for earlier releases.
 
 [`memo-parser`]: ./memo-parser/README.md
 
+[#1472]: https://github.com/benmosher/eslint-plugin-import/pull/1472
 [#1470]: https://github.com/benmosher/eslint-plugin-import/pull/1470
 [#1435]: https://github.com/benmosher/eslint-plugin-import/pull/1435
 [#1425]: https://github.com/benmosher/eslint-plugin-import/pull/1425
@@ -981,3 +985,4 @@ for info on changes for earlier releases.
 [@sharmilajesupaul]: https://github.com/sharmilajesupaul
 [@lencioni]: https://github.com/lencioni
 [@JounQin]: https://github.com/JounQin
+[@atikenny]: https://github.com/atikenny

docs/rules/group-exports.md

@@ -26,6 +26,12 @@ export {
 }
 ```
 
+```js
+// Aggregating exports -> ok
+export { default as module1 } from 'module-1'
+export { default as module2 } from 'module-2'
+```
+
 ```js
 // A single exports assignment -> ok
 module.exports = {
@@ -63,6 +69,12 @@ export const first = true
 export const second = true
 ```
 
+```js
+// Aggregating exports from the same module -> not ok!
+export { module1 } from 'module-1'
+export { module2 } from 'module-1'
+```
+
 ```js
 // Multiple exports assignments -> not ok!
 exports.first = true

package.json

@@ -81,6 +81,7 @@
   },
   "dependencies": {
     "array-includes": "^3.0.3",
+    "array.prototype.flat": "^1.2.1",
     "contains-path": "^0.1.0",
     "debug": "^2.6.9",
     "doctrine": "1.5.0",

src/rules/group-exports.js

@@ -1,4 +1,6 @@
 import docsUrl from '../docsUrl'
+import values from 'object.values'
+import flat from 'array.prototype.flat'
 
 const meta = {
   type: 'suggestion',
@@ -46,11 +48,18 @@ function create(context) {
   const nodes = {
     modules: new Set(),
     commonjs: new Set(),
+    sources: {},
   }
 
   return {
     ExportNamedDeclaration(node) {
-      nodes.modules.add(node)
+      if (!node.source) {
+        nodes.modules.add(node)
+      } else if (Array.isArray(nodes.sources[node.source.value])) {
+        nodes.sources[node.source.value].push(node)
+      } else {
+        nodes.sources[node.source.value] = [node]
+      }
     },
 
     AssignmentExpression(node) {
@@ -86,6 +95,16 @@ function create(context) {
         })
       }
 
+      // Report multiple `aggregated exports` from the same module (ES2015 modules)
+      flat(values(nodes.sources)
+        .filter(nodesWithSource => Array.isArray(nodesWithSource) && nodesWithSource.length > 1))
+        .forEach((node) => {
+          context.report({
+            node,
+            message: errors[node.type],
+          })
+        })
+
       // Report multiple `module.exports` assignments (CommonJS)
       if (nodes.commonjs.size > 1) {
         nodes.commonjs.forEach(node => {

tests/src/rules/group-exports.js

@@ -45,6 +45,10 @@ ruleTester.run('group-exports', rule, {
       // test
       export default {}
     ` }),
+    test({ code: `
+      export { default as module1 } from './module-1'
+      export { default as module2 } from './module-2'
+    ` }),
     test({ code: 'module.exports = {} '}),
     test({ code: `
       module.exports = { test: true,
@@ -111,6 +115,16 @@ ruleTester.run('group-exports', rule, {
         errors.named,
       ],
     }),
+    test({
+      code: `
+        export { method1 } from './module-1'
+        export { method2 } from './module-1'
+      `,
+      errors: [
+        errors.named,
+        errors.named,
+      ],
+    }),
     test({
       code: `
         module.exports = {}