[Fix] prefer-default-export: Skips warning on a single type declara…

…tion or type alias.

Fixes #1332.

src/rules/prefer-default-export.js

@@ -47,9 +47,12 @@ module.exports = {
         // if there are specifiers, node.declaration should be null
         if (!node.declaration) return
 
-        // don't count flow types exports
+        // don't warn on single type aliases or declarations
         if (node.exportKind === 'type') return
 
+        if (node.declaration.type === 'TSTypeAliasDeclaration'
+          || node.declaration.type === 'TypeAlias') return
+
         if (node.declaration.declarations) {
           node.declaration.declarations.forEach(function(declaration) {
             captureDeclaration(declaration.id)

tests/src/rules/prefer-default-export.js

@@ -1,10 +1,22 @@
 import { test } from '../utils'
 
 import { RuleTester } from 'eslint'
+import eslintPkg from 'eslint/package.json'
+import semver from 'semver';
 
 const ruleTester = new RuleTester()
     , rule = require('rules/prefer-default-export')
 
+// Typescript
+const parsers = [require.resolve('babel-eslint')];
+if (semver.satisfies(eslintPkg.version, '>5.0.0')) {
+  parsers.push(require.resolve('@typescript-eslint/parser'))
+}
+
+if (semver.satisfies(eslintPkg.version, '<6.0.0')) {
+  parsers.push(require.resolve('typescript-eslint-parser'))
+}
+
 ruleTester.run('prefer-default-export', rule, {
   valid: [
     test({
@@ -72,7 +84,7 @@ ruleTester.run('prefer-default-export', rule, {
     test({
       code: `export type UserId = number;`,
       parser: require.resolve('babel-eslint'),
-      }),
+    }),
 
     // issue #653
     test({
@@ -84,6 +96,29 @@ ruleTester.run('prefer-default-export', rule, {
       parser: require.resolve('babel-eslint'),
     }),
 
+    // Exporting types
+    ...parsers.map(parser => test({
+      code: `
+        export type foo = string;
+        export type bar = number;`,
+      parser,
+    })),
+    ...parsers.map(parser => test({
+      code: 'export type foo = string',
+      parser,
+    })),
+    ...parsers.map(parser => test({
+      code: `
+        type foo = 'foo';
+        export { foo };`,
+      parser,
+    })),
+    ...parsers.map(parser => test({
+      code: `
+        type foo = 'foo';
+        export { foo as bar };`,
+      parser,
+    })),
     // ...SYNTAX_CASES,
   ],
   invalid: [