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

Author: rfermann

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()
@@ -391,6 +392,7 @@ module.exports = {
       }
 
       exports = exportList.get(file)
+      console.log('file: ', file)
 
       // special case: export * from
       const exportAll = exports.get(EXPORT_ALL_DECLARATION)
@@ -409,8 +411,10 @@ module.exports = {
       }
 
       const exportStatement = exports.get(exportedValue)
+      console.log('exportStatement: ', exportStatement)
 
       const value = exportedValue === IMPORT_DEFAULT_SPECIFIER ? DEFAULT : exportedValue
+      console.log('value: ', value)
 
       if (typeof exportStatement !== 'undefined'){
         if (exportStatement.whereUsed.size < 1) {
@@ -463,7 +467,8 @@ 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 +793,8 @@ 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`),
+        ],
+      }),
+    ],
+  })
+})