Merge pull request #1142 from rfermann/master

New: `no-unused-modules` rule

Author: ljharb

docs/rules/no-unused-modules.md

@@ -0,0 +1,101 @@
+# import/no-unused-modules
+
+Reports:
+  - modules without any exports
+  - individual exports not being statically `import`ed or `require`ed from other modules in the same project
+
+Note: dynamic imports are currently not supported.
+
+## Rule Details
+
+
+### Options
+
+This rule takes the following option:
+
+- `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) 
+- `missingExports`: if `true`, files without any exports are reported  
+- `unusedExports`: if `true`, exports without any static usage within other modules are reported.
+
+
+### Example for missing exports
+#### The following will be reported
+```js
+const class MyClass { /*...*/ } 
+
+function makeClass() { return new MyClass(...arguments) }
+```
+
+#### The following will not be reported
+
+```js
+export default function () { /*...*/ } 
+```
+```js
+export const foo = function () { /*...*/ } 
+```
+```js
+export { foo, bar }
+```
+```js
+export { foo as bar }
+```
+
+### Example for unused exports
+given file-f:
+```js
+import { e } from 'file-a'
+import { f } from 'file-b'
+import * from  'file-c'
+export * from 'file-d'
+export { default, i0 } from 'file-e' // both will be reported
+
+export const j = 99 // will be reported 
+```
+and file-e:
+```js
+export const i0 = 9 // will not be reported
+export const i1 = 9 // will be reported
+export default () => {} // will not be reported
+```
+and file-d:
+```js
+export const h = 8 // will not be reported
+export default () => {} // will be reported, as export * only considers named exports and ignores default exports
+```
+and file-c:
+```js
+export const g = 7 // will not be reported
+export default () => {} // will not be reported
+```
+and file-b:
+```js
+import two, { b, c, doAnything } from 'file-a'
+
+export const f = 6 // will not be reported
+```
+and file-a:
+```js
+const b = 2
+const c = 3
+const d = 4
+
+export const a = 1 // will be reported
+
+export { b, c } // will not be reported
+
+export { d as e } // will not be reported
+
+export function doAnything() {
+  // some code
+}  // will not be reported
+
+export default 5 // will not be reported
+```
+
+
+
+## When not to use
+
+If you don't mind having unused files or dead code within your codebase, you can disable this rule

src/ExportMap.js

@@ -397,6 +397,18 @@ ExportMap.parse = function (path, content, context) {
 
   function captureDependency(declaration) {
     if (declaration.source == null) return null
+    const importedSpecifiers = new Set()
+    const supportedTypes = new Set(['ImportDefaultSpecifier', 'ImportNamespaceSpecifier'])
+    if (declaration.specifiers) {
+      declaration.specifiers.forEach(specifier => {
+        if (supportedTypes.has(specifier.type)) {
+          importedSpecifiers.add(specifier.type)
+        }
+        if (specifier.type === 'ImportSpecifier') {
+          importedSpecifiers.add(specifier.local.name)
+        }
+      })
+    }
 
     const p = remotePath(declaration.source.value)
     if (p == null) return null
@@ -410,6 +422,7 @@ ExportMap.parse = function (path, content, context) {
         value: declaration.source.value,
         loc: declaration.source.loc,
       },
+      importedSpecifiers,
     })
     return getter
   }

src/index.js

@@ -18,6 +18,7 @@ export const rules = {
   'no-named-as-default': require('./rules/no-named-as-default'),
   'no-named-as-default-member': require('./rules/no-named-as-default-member'),
   'no-anonymous-default-export': require('./rules/no-anonymous-default-export'),
+  'no-unused-modules': require('./rules/no-unused-modules'),
 
   'no-commonjs': require('./rules/no-commonjs'),
   'no-amd': require('./rules/no-amd'),