Add no-named-export + docs/tests (#1157)

* Add `no-named-export` + docs/tests

* Fix no-named-export docs missing quotes

* Fix ruleId in no-named-export case test

* Tighten no-named-export error message

README.md

@@ -86,6 +86,7 @@ This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, a
 * Forbid unassigned imports ([`no-unassigned-import`])
 * Forbid named default exports ([`no-named-default`])
 * Forbid default exports ([`no-default-export`])
+* Forbid named exports ([`no-named-export`])
 * Forbid anonymous values as default exports ([`no-anonymous-default-export`])
 * Prefer named exports to be grouped together in a single export declaration ([`group-exports`])
 * Enforce a leading comment with the webpackChunkName for dynamic imports ([`dynamic-import-chunkname`])
@@ -104,6 +105,7 @@ This plugin intends to support linting of ES2015+ (ES6+) import/export syntax, a
 [`no-anonymous-default-export`]: ./docs/rules/no-anonymous-default-export.md
 [`group-exports`]: ./docs/rules/group-exports.md
 [`no-default-export`]: ./docs/rules/no-default-export.md
+[`no-named-export`]: ./docs/rules/no-named-export.md
 [`dynamic-import-chunkname`]: ./docs/rules/dynamic-import-chunkname.md
 
 ## Installation

docs/rules/no-named-export.md

@@ -0,0 +1,77 @@
+# no-named-export
+
+Prohibit named exports. Mostly an inverse of [`no-default-export`].
+
+[`no-default-export`]: ./no-default-export.md
+
+## Rule Details
+
+The following patterns are considered warnings:
+
+```javascript
+// bad1.js
+
+// There is only a single module export and it's a named export.
+export const foo = 'foo';
+```
+
+```javascript
+// bad2.js
+
+// There is more than one named export in the module.
+export const foo = 'foo';
+export const bar = 'bar';
+```
+
+```javascript
+// bad3.js
+
+// There is more than one named export in the module.
+const foo = 'foo';
+const bar = 'bar';
+export { foo, bar }
+```
+
+```javascript
+// bad4.js
+
+// There is more than one named export in the module.
+export * from './other-module'
+```
+
+```javascript
+// bad5.js
+
+// There is a default and a named export.
+export const foo = 'foo';
+const bar = 'bar';
+export default 'bar';
+```
+
+The following patterns are not warnings:
+
+```javascript
+// good1.js
+
+// There is only a single module export and it's a default export.
+export default 'bar';
+```
+
+```javascript
+// good2.js
+
+// There is only a single module export and it's a default export.
+const foo = 'foo';
+export { foo as default }
+```
+
+```javascript
+// good3.js
+
+// There is only a single module export and it's a default export.
+export default from './other-module';
+```
+
+## When Not To Use It
+
+If you don't care if named imports are used, or if you prefer named imports over default imports.

src/index.js

@@ -32,6 +32,7 @@ export const rules = {
   'newline-after-import': require('./rules/newline-after-import'),
   'prefer-default-export': require('./rules/prefer-default-export'),
   'no-default-export': require('./rules/no-default-export'),
+  'no-named-export': require('./rules/no-named-export'),
   'no-dynamic-require': require('./rules/no-dynamic-require'),
   'unambiguous': require('./rules/unambiguous'),
   'no-unassigned-import': require('./rules/no-unassigned-import'),

src/rules/no-named-export.js

@@ -0,0 +1,33 @@
+import docsUrl from '../docsUrl'
+
+module.exports = {
+  meta: {
+    docs: { url: docsUrl('no-named-export') },
+  },
+
+  create(context) {
+    // ignore non-modules
+    if (context.parserOptions.sourceType !== 'module') {
+      return {}
+    }
+
+    const message = 'Named exports are not allowed.'
+
+    return {
+      ExportAllDeclaration(node) {
+        context.report({node, message})
+      },
+
+      ExportNamedDeclaration(node) {
+        if (node.specifiers.length === 0) {
+          return context.report({node, message})
+        }
+
+        const someNamed = node.specifiers.some(specifier => specifier.exported.name !== 'default')
+        if (someNamed) {
+          context.report({node, message})
+        }
+      },
+    }
+  },
+}

tests/src/rules/no-named-export.js

@@ -0,0 +1,179 @@
+import { RuleTester } from 'eslint'
+import { test } from '../utils'
+
+const ruleTester = new RuleTester()
+    , rule = require('rules/no-named-export')
+
+ruleTester.run('no-named-export', rule, {
+  valid: [
+    test({
+      code: 'export default function bar() {};',
+    }),
+    test({
+      code: 'export { foo as default }',
+    }),
+    test({
+      code: 'export default from "foo.js"',
+      parser: 'babel-eslint',
+    }),
+
+    // no exports at all
+    test({
+      code: `import * as foo from './foo';`,
+    }),
+    test({
+      code: `import foo from './foo';`,
+    }),
+    test({
+      code: `import {default as foo} from './foo';`,
+    }),
+  ],
+  invalid: [
+    test({
+      code: `
+        export const foo = 'foo';
+        export const bar = 'bar';
+      `,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }, {
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `
+        export const foo = 'foo';
+        export default bar;`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `
+        export const foo = 'foo';
+        export function bar() {};
+      `,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }, {
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export const foo = 'foo';`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `
+        const foo = 'foo';
+        export { foo };
+      `,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export { foo, bar }`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export const { foo, bar } = item;`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export const { foo, bar: baz } = item;`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export const { foo: { bar, baz } } = item;`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `
+        export const foo = item;
+        export { item };
+      `,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }, {
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export * from './foo';`,
+      errors: [{
+        ruleId: 'ExportAllDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export const { foo } = { foo: "bar" };`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export const { foo: { bar } } = { foo: { bar: "baz" } };`,
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: 'export { a, b } from "foo.js"',
+      parser: 'babel-eslint',
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export type UserId = number;`,
+      parser: 'babel-eslint',
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: 'export foo from "foo.js"',
+      parser: 'babel-eslint',
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+    test({
+      code: `export Memory, { MemoryValue } from './Memory'`,
+      parser: 'babel-eslint',
+      errors: [{
+        ruleId: 'ExportNamedDeclaration',
+        message: 'Named exports are not allowed.',
+      }],
+    }),
+  ],
+})