[flow] no-unused-modules: add flow type support

CHANGELOG.md

@@ -11,6 +11,7 @@ This change log adheres to standards from [Keep a CHANGELOG](http://keepachangel
 - [`no-namespace`]: Make rule fixable ([#1401], thanks [@TrevorBurnham])
 - support `parseForESLint` from custom parser ([#1435], thanks [@JounQin])
 - [`no-extraneous-dependencies`]: Implement support for [bundledDependencies](https://npm.github.io/using-pkgs-docs/package-json/types/bundleddependencies.html) ([#1436], thanks [@schmidsi]))
+- [`no-unused-modules`]: add flow type support ([#1542], thanks [@rfermann])
 
 ### Fixed
 - [`default`]: make error message less confusing ([#1470], thanks [@golopot])
@@ -620,6 +621,7 @@ for info on changes for earlier releases.
 [`memo-parser`]: ./memo-parser/README.md
 
 [#1551]: https://github.com/benmosher/eslint-plugin-import/pull/1551
+[#1542]: https://github.com/benmosher/eslint-plugin-import/pull/1542
 [#1521]: https://github.com/benmosher/eslint-plugin-import/pull/1521
 [#1519]: https://github.com/benmosher/eslint-plugin-import/pull/1519
 [#1507]: https://github.com/benmosher/eslint-plugin-import/pull/1507

src/rules/no-unused-modules.js

@@ -42,6 +42,7 @@ const VARIABLE_DECLARATION = 'VariableDeclaration'
 const FUNCTION_DECLARATION = 'FunctionDeclaration'
 const CLASS_DECLARATION = 'ClassDeclaration'
 const DEFAULT = 'default'
+const TYPE_ALIAS = 'TypeAlias'
 
 let preparationDone = false
 const importList = new Map()
@@ -463,7 +464,8 @@ module.exports = {
           if (declaration) {
             if (
               declaration.type === FUNCTION_DECLARATION ||
-              declaration.type === CLASS_DECLARATION
+              declaration.type === CLASS_DECLARATION ||
+              declaration.type === TYPE_ALIAS
             ) {
               newExportIdentifiers.add(declaration.id.name)
             }
@@ -788,7 +790,8 @@ module.exports = {
         if (node.declaration) {
           if (
             node.declaration.type === FUNCTION_DECLARATION ||
-            node.declaration.type === CLASS_DECLARATION
+            node.declaration.type === CLASS_DECLARATION ||
+            node.declaration.type === TYPE_ALIAS
           ) {
             checkUsage(node, node.declaration.id.name)
           }

tests/files/no-unused-modules/flow-0.js

@@ -0,0 +1 @@
+import { type FooType } from './flow-2';

tests/files/no-unused-modules/flow-1.js

@@ -0,0 +1,2 @@
+// @flow strict
+export type Bar = number;

tests/files/no-unused-modules/flow-2.js

@@ -0,0 +1,2 @@
+// @flow strict
+export type FooType = string;

tests/src/rules/no-unused-modules.js

@@ -638,3 +638,35 @@ describe('do not report unused export for files mentioned in package.json', () =
     ],
   })
 })
+
+describe('correctly report flow types', () => {
+  ruleTester.run('no-unused-modules', rule, {
+    valid: [
+      test({
+        options: unusedExportsOptions,
+        code: 'import { type FooType } from "./flow-2";',
+        parser: require.resolve('babel-eslint'),
+        filename: testFilePath('./no-unused-modules/flow-0.js'),
+      }),
+      test({
+        options: unusedExportsOptions,
+        code: `// @flow strict
+               export type FooType = string;`,
+        parser: require.resolve('babel-eslint'),
+        filename: testFilePath('./no-unused-modules/flow-2.js'),
+      }),
+    ],
+    invalid: [
+      test({
+        options: unusedExportsOptions,
+        code: `// @flow strict
+               export type Bar = string;`,
+        parser: require.resolve('babel-eslint'),
+        filename: testFilePath('./no-unused-modules/flow-1.js'),
+        errors: [
+          error(`exported declaration 'Bar' not used within other modules`),
+        ],
+      }),
+    ],
+  })
+})