[New] no-unused-modules: Add ignoreUnusedTypeExports option

Fixes #2694

Author: silverwind

CHANGELOG.md

@@ -9,6 +9,7 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 ### Added
 - [`dynamic-import-chunkname`]: add `allowEmpty` option to allow empty leading comments ([#2942], thanks [@JiangWeixian])
 - [`dynamic-import-chunkname`]: Allow empty chunk name when webpackMode: 'eager' is set; add suggestions to remove name in eager mode ([#3004], thanks [@amsardesai])
+- [`no-unused-modules`]: Add `ignoreUnusedTypeExports` option ([#3011], thanks [@silverwind])
 
 ### Fixed
 - [`no-extraneous-dependencies`]: allow wrong path ([#3012], thanks [@chabb])
@@ -1120,6 +1121,7 @@ for info on changes for earlier releases.
 [`memo-parser`]: ./memo-parser/README.md
 
 [#3012]: https://github.com/import-js/eslint-plugin-import/pull/3012
+[#3011]: https://github.com/import-js/eslint-plugin-import/pull/3011
 [#3004]: https://github.com/import-js/eslint-plugin-import/pull/3004
 [#2991]: https://github.com/import-js/eslint-plugin-import/pull/2991
 [#2989]: https://github.com/import-js/eslint-plugin-import/pull/2989
@@ -1915,6 +1917,7 @@ for info on changes for earlier releases.
 [@sergei-startsev]: https://github.com/sergei-startsev
 [@sharmilajesupaul]: https://github.com/sharmilajesupaul
 [@sheepsteak]: https://github.com/sheepsteak
+[@silverwind]: https://github.com/silverwind
 [@silviogutierrez]: https://github.com/silviogutierrez
 [@SimenB]: https://github.com/SimenB
 [@simmo]: https://github.com/simmo

docs/rules/no-unused-modules.md

@@ -29,8 +29,9 @@ This rule takes the following option:
 
  - **`missingExports`**: if `true`, files without any exports are reported (defaults to `false`)
  - **`unusedExports`**: if `true`, exports without any static usage within other modules are reported (defaults to `false`)
- - `src`: an array with files/paths to be analyzed. It only applies to unused exports. Defaults to `process.cwd()`, if not provided
- - `ignoreExports`: an array with files/paths for which unused exports will not be reported (e.g module entry points in a published package)
+ - **`ignoreUnusedTypeExports`**: if `true`, TypeScript type exports without any static usage within other modules are reported (defaults to `false` and has no effect unless `unusedExports` is `true`)
+ - **`src`**: an array with files/paths to be analyzed. It only applies to unused exports. Defaults to `process.cwd()`, if not provided
+ - **`ignoreExports`**: an array with files/paths for which unused exports will not be reported (e.g module entry points in a published package)
 
 ### Example for missing exports
 
@@ -116,6 +117,16 @@ export function doAnything() {
 export default 5 // will not be reported
 ```
 
+### Unused exports with `ignoreUnusedTypeExports` set to `true`
+
+The following will not be reported:
+
+```ts
+export type Foo = {}; // will not be reported
+export interface Foo = {}; // will not be reported
+export enum Foo {}; // will not be reported
+```
+
 #### Important Note
 
 Exports from files listed as a main file (`main`, `browser`, or `bin` fields in `package.json`) will be ignored by default. This only applies if the `package.json` is not set to `private: true`

src/rules/no-unused-modules.js

@@ -83,28 +83,30 @@ const DEFAULT = 'default';
 
 function forEachDeclarationIdentifier(declaration, cb) {
   if (declaration) {
+    const isTypeDeclaration = declaration.type === TS_INTERFACE_DECLARATION
+      || declaration.type === TS_TYPE_ALIAS_DECLARATION
+      || declaration.type === TS_ENUM_DECLARATION;
+
     if (
       declaration.type === FUNCTION_DECLARATION
       || declaration.type === CLASS_DECLARATION
-      || declaration.type === TS_INTERFACE_DECLARATION
-      || declaration.type === TS_TYPE_ALIAS_DECLARATION
-      || declaration.type === TS_ENUM_DECLARATION
+      || isTypeDeclaration
     ) {
-      cb(declaration.id.name);
+      cb(declaration.id.name, isTypeDeclaration);
     } else if (declaration.type === VARIABLE_DECLARATION) {
       declaration.declarations.forEach(({ id }) => {
         if (id.type === OBJECT_PATTERN) {
           recursivePatternCapture(id, (pattern) => {
             if (pattern.type === IDENTIFIER) {
-              cb(pattern.name);
+              cb(pattern.name, false);
             }
           });
         } else if (id.type === ARRAY_PATTERN) {
           id.elements.forEach(({ name }) => {
-            cb(name);
+            cb(name, false);
           });
         } else {
-          cb(id.name);
+          cb(id.name, false);
         }
       });
     }
@@ -443,6 +445,10 @@ module.exports = {
           description: 'report exports without any usage',
           type: 'boolean',
         },
+        ignoreUnusedTypeExports: {
+          description: 'ignore type exports without any usage',
+          type: 'boolean',
+        },
       },
       anyOf: [
         {
@@ -470,6 +476,7 @@ module.exports = {
       ignoreExports = [],
       missingExports,
       unusedExports,
+      ignoreUnusedTypeExports,
     } = context.options[0] || {};
 
     if (unusedExports) {
@@ -502,11 +509,15 @@ module.exports = {
       exportCount.set(IMPORT_NAMESPACE_SPECIFIER, namespaceImports);
     };
 
-    const checkUsage = (node, exportedValue) => {
+    const checkUsage = (node, exportedValue, isTypeExport) => {
       if (!unusedExports) {
         return;
       }
 
+      if (isTypeExport && ignoreUnusedTypeExports) {
+        return;
+      }
+
       if (ignoredFiles.has(file)) {
         return;
       }
@@ -935,14 +946,14 @@ module.exports = {
         checkExportPresence(node);
       },
       ExportDefaultDeclaration(node) {
-        checkUsage(node, IMPORT_DEFAULT_SPECIFIER);
+        checkUsage(node, IMPORT_DEFAULT_SPECIFIER, false);
       },
       ExportNamedDeclaration(node) {
         node.specifiers.forEach((specifier) => {
-          checkUsage(specifier, specifier.exported.name || specifier.exported.value);
+          checkUsage(specifier, specifier.exported.name || specifier.exported.value, false);
         });
-        forEachDeclarationIdentifier(node.declaration, (name) => {
-          checkUsage(node, name);
+        forEachDeclarationIdentifier(node.declaration, (name, isTypeExport) => {
+          checkUsage(node, name, isTypeExport);
         });
       },
     };

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

@@ -38,6 +38,13 @@ const unusedExportsTypescriptOptions = [{
   ignoreExports: undefined,
 }];
 
+const unusedExportsTypescriptIgnoreUnusedTypesOptions = [{
+  unusedExports: true,
+  ignoreUnusedTypeExports: true,
+  src: [testFilePath('./no-unused-modules/typescript')],
+  ignoreExports: undefined,
+}];
+
 const unusedExportsJsxOptions = [{
   unusedExports: true,
   src: [testFilePath('./no-unused-modules/jsx')],
@@ -1209,6 +1216,66 @@ context('TypeScript', function () {
   });
 });
 
+describe('ignoreUnusedTypeExports', () => {
+  getTSParsers().forEach((parser) => {
+    typescriptRuleTester.run('no-unused-modules', rule, {
+      valid: [
+        // unused vars should not report
+        test({
+          options: unusedExportsTypescriptIgnoreUnusedTypesOptions,
+          code: `export interface c {};`,
+          parser,
+          filename: testFilePath(
+            './no-unused-modules/typescript/file-ts-c-unused.ts',
+          ),
+        }),
+        test({
+          options: unusedExportsTypescriptIgnoreUnusedTypesOptions,
+          code: `export type d = {};`,
+          parser,
+          filename: testFilePath(
+            './no-unused-modules/typescript/file-ts-d-unused.ts',
+          ),
+        }),
+        test({
+          options: unusedExportsTypescriptIgnoreUnusedTypesOptions,
+          code: `export enum e { f };`,
+          parser,
+          filename: testFilePath(
+            './no-unused-modules/typescript/file-ts-e-unused.ts',
+          ),
+        }),
+        // used vars should not report
+        test({
+          options: unusedExportsTypescriptIgnoreUnusedTypesOptions,
+          code: `export interface c {};`,
+          parser,
+          filename: testFilePath(
+            './no-unused-modules/typescript/file-ts-c-used-as-type.ts',
+          ),
+        }),
+        test({
+          options: unusedExportsTypescriptIgnoreUnusedTypesOptions,
+          code: `export type d = {};`,
+          parser,
+          filename: testFilePath(
+            './no-unused-modules/typescript/file-ts-d-used-as-type.ts',
+          ),
+        }),
+        test({
+          options: unusedExportsTypescriptIgnoreUnusedTypesOptions,
+          code: `export enum e { f };`,
+          parser,
+          filename: testFilePath(
+            './no-unused-modules/typescript/file-ts-e-used-as-type.ts',
+          ),
+        }),
+      ],
+      invalid: [],
+    });
+  });
+});
+
 describe('correctly work with JSX only files', () => {
   jsxRuleTester.run('no-unused-modules', rule, {
     valid: [