no-unused-modules: support dynamic imports

All occurences of `import('...')` are treated as namespace imports
(`import * as X from '...'`)

Author: maxkomarychev

CHANGELOG.md

@@ -6,6 +6,10 @@ This change log adheres to standards from [Keep a CHANGELOG](http://keepachangel
 
 ## [Unreleased]
 
+### Added
+
+- [`no-unused-modules`]: support dynamic imports ([#1660], thanks [@maxkomarychev])
+
 ### Fixed
 - [`group-exports`]: Flow type export awareness ([#1702], thanks [@ernestostifano])
 - [`order`]: Recognize pathGroup config for first group ([#1719], [#1724], thanks [@forivall], [@xpl])

docs/rules/no-unused-modules.md

@@ -3,8 +3,8 @@
 Reports:
   - modules without any exports
   - individual exports not being statically `import`ed or `require`ed from other modules in the same project
+  - dynamic imports are supported if argument is a literal string
 
-Note: dynamic imports are currently not supported.
 
 ## Rule Details
 

src/ExportMap.js

@@ -7,6 +7,7 @@ import debug from 'debug'
 import { SourceCode } from 'eslint'
 
 import parse from 'eslint-module-utils/parse'
+import visit from 'eslint-module-utils/visit'
 import resolve from 'eslint-module-utils/resolve'
 import isIgnored, { hasValidExtension } from 'eslint-module-utils/ignore'
 
@@ -344,14 +345,43 @@ ExportMap.parse = function (path, content, context) {
   var m = new ExportMap(path)
 
   try {
-    var ast = parse(path, content, context)
+    var { ast, visitorKeys } = parse(path, content, context)
   } catch (err) {
-    log('parse error:', path, err)
     m.errors.push(err)
     return m // can't continue
   }
 
-  if (!unambiguous.isModule(ast)) return null
+  let hasDynamicImports = false
+
+  visit(ast, visitorKeys, {
+    CallExpression(node) {
+      if (node.callee.type === 'Import') {
+        hasDynamicImports = true
+        const firstArgument = node.arguments[0]
+        if (firstArgument.type !== 'Literal') {
+          return null
+        }
+        const p = remotePath(firstArgument.value)
+        if (p == null) {
+          return null
+        }
+        const importedSpecifiers = new Set()
+        importedSpecifiers.add('ImportNamespaceSpecifier')
+        const getter = thunkFor(p, context)
+        m.imports.set(p, {
+          getter,
+          source: {
+            // capturing actual node reference holds full AST in memory!
+            value: firstArgument.value,
+            loc: firstArgument.loc,
+          },
+          importedSpecifiers,
+        })
+      }
+    },
+  })
+
+  if (!unambiguous.isModule(ast) && !hasDynamicImports) return null
 
   const docstyle = (context.settings && context.settings['import/docstyle']) || ['jsdoc']
   const docStyleParsers = {}

tests/files/no-unused-modules/dynamic-import-js-2.js

@@ -0,0 +1,13 @@
+const importPath = './exports-for-dynamic-js';
+class A {
+    method() {
+        const c = import(importPath)
+    }
+}
+
+
+class B {
+    method() {
+        const c = import('i-do-not-exist')
+    }
+}

tests/files/no-unused-modules/dynamic-import-js.js

@@ -0,0 +1,5 @@
+class A {
+    method() {
+        const c = import('./exports-for-dynamic-js')
+    }
+}

tests/files/no-unused-modules/exports-for-dynamic-js-2.js

@@ -0,0 +1,5 @@
+export const a = 10;
+export const b = 20;
+export const c = 30;
+const d = 40;
+export default d;

tests/files/no-unused-modules/exports-for-dynamic-js.js

@@ -0,0 +1,5 @@
+export const a = 10
+export const b = 20
+export const c = 30
+const d = 40
+export default d

tests/files/no-unused-modules/typescript/dynamic-import-ts.ts

@@ -0,0 +1,6 @@
+class A {
+    method() {
+        const c = import('./exports-for-dynamic-ts')
+    }
+}
+

tests/files/no-unused-modules/typescript/exports-for-dynamic-ts.ts

@@ -0,0 +1,5 @@
+export const ts_a = 10
+export const ts_b = 20
+export const ts_c = 30
+const ts_d = 40
+export default ts_d

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

@@ -1,4 +1,4 @@
-import { test, testFilePath } from '../utils'
+import { test, testFilePath } from '../../src/utils'
 import jsxConfig from '../../../config/react'
 import typescriptConfig from '../../../config/typescript'
 
@@ -71,32 +71,39 @@ ruleTester.run('no-unused-modules', rule, {
 // tests for  exports
 ruleTester.run('no-unused-modules', rule, {
   valid: [
-
     test({ options: unusedExportsOptions,
            code: 'import { o2 } from "./file-o";export default () => 12',
-           filename: testFilePath('./no-unused-modules/file-a.js')}),
+           filename: testFilePath('./no-unused-modules/file-a.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'export const b = 2',
-           filename: testFilePath('./no-unused-modules/file-b.js')}),
+           filename: testFilePath('./no-unused-modules/file-b.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'const c1 = 3; function c2() { return 3 }; export { c1, c2 }',
-           filename: testFilePath('./no-unused-modules/file-c.js')}),
+           filename: testFilePath('./no-unused-modules/file-c.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'export function d() { return 4 }',
-           filename: testFilePath('./no-unused-modules/file-d.js')}),
+           filename: testFilePath('./no-unused-modules/file-d.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'export class q { q0() {} }',
-           filename: testFilePath('./no-unused-modules/file-q.js')}),
+           filename: testFilePath('./no-unused-modules/file-q.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'const e0 = 5; export { e0 as e }',
-           filename: testFilePath('./no-unused-modules/file-e.js')}),
+           filename: testFilePath('./no-unused-modules/file-e.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'const l0 = 5; const l = 10; export { l0 as l1, l }; export default () => {}',
-           filename: testFilePath('./no-unused-modules/file-l.js')}),
+           filename: testFilePath('./no-unused-modules/file-l.js'),
+           parser: require.resolve('babel-eslint')}),
     test({ options: unusedExportsOptions,
            code: 'const o0 = 0; const o1 = 1; export { o0, o1 as o2 }; export default () => {}',
-           filename: testFilePath('./no-unused-modules/file-o.js')}),
-    ],
+           filename: testFilePath('./no-unused-modules/file-o.js'),
+           parser: require.resolve('babel-eslint')}),
+  ],
   invalid: [
     test({ options: unusedExportsOptions,
            code: `import eslint from 'eslint'
@@ -164,6 +171,56 @@ ruleTester.run('no-unused-modules', rule, {
   ],
 })
 
+// test for unused exports with `import()`
+ruleTester.run('no-unused-modules', rule, {
+  valid: [
+    test({ options: unusedExportsOptions,
+           code: `
+           export const a = 10
+           export const b = 20
+           export const c = 30
+           const d = 40
+           export default d
+           `,
+           parser: require.resolve('babel-eslint'),
+           filename: testFilePath('./no-unused-modules/exports-for-dynamic-js.js')}),
+  ],
+  invalid: [
+    test({ options: unusedExportsOptions,
+      code: `
+      export const a = 10
+      export const b = 20
+      export const c = 30
+      const d = 40
+      export default d
+      `,
+      parser: require.resolve('babel-eslint'),
+      filename: testFilePath('./no-unused-modules/exports-for-dynamic-js-2.js'),
+      errors: [
+           error(`exported declaration 'a' not used within other modules`),
+           error(`exported declaration 'b' not used within other modules`),
+           error(`exported declaration 'c' not used within other modules`),
+           error(`exported declaration 'default' not used within other modules`),
+      ]}),
+  ],
+})
+typescriptRuleTester.run('no-unused-modules', rule, {
+  valid: [
+    test({ options: unusedExportsTypescriptOptions,
+           code: `
+           export const ts_a = 10
+           export const ts_b = 20
+           export const ts_c = 30
+           const ts_d = 40
+           export default ts_d
+           `,
+           parser: require.resolve('@typescript-eslint/parser'),
+           filename: testFilePath('./no-unused-modules/typescript/exports-for-dynamic-ts.ts')}),
+  ],
+  invalid: [
+  ],
+})
+
 // // test for export from
 ruleTester.run('no-unused-modules', rule, {
   valid: [

utils/parse.js

@@ -3,9 +3,33 @@ exports.__esModule = true
 
 const moduleRequire = require('./module-require').default
 const extname = require('path').extname
+const fs = require('fs')
 
 const log = require('debug')('eslint-plugin-import:parse')
 
+function getBabelVisitorKeys(parserPath) {
+  const hypotheticalLocation = parserPath.replace('index.js', 'visitor-keys.js')
+  if (fs.existsSync(hypotheticalLocation)) {
+    const keys = moduleRequire(parserPath.replace('index.js', 'visitor-keys.js'))
+    return keys
+  } else {
+    return null
+  }
+}
+
+function keysFromParser(parserPath, parserInstance, parsedResult) {
+  if (/.*espree.*/.test(parserPath)) {
+    return parserInstance.VisitorKeys
+  } else if (/.*babel-eslint.*/.test(parserPath)) {
+    return getBabelVisitorKeys(parserPath)
+  } else if (/.*@typescript-eslint\/parser/.test(parserPath)) {
+    if (parsedResult) {
+      return parsedResult.visitorKeys 
+    }
+  }
+  return null
+}
+
 exports.default = function parse(path, content, context) {
 
   if (context == null) throw new Error('need context to parse properly')
@@ -45,7 +69,12 @@ exports.default = function parse(path, content, context) {
   if (typeof parser.parseForESLint === 'function') {
     let ast
     try {
-      ast = parser.parseForESLint(content, parserOptions).ast
+      const parserRaw = parser.parseForESLint(content, parserOptions)
+      ast = parserRaw.ast
+      return {
+        ast,
+        visitorKeys: keysFromParser(parserPath, parser, parserRaw),
+      }
     } catch (e) {
       console.warn()
       console.warn('Error while parsing ' + parserOptions.filePath)
@@ -55,16 +84,25 @@ exports.default = function parse(path, content, context) {
       console.warn(
         '`parseForESLint` from parser `' +
           parserPath +
-          '` is invalid and will just be ignored'
+          '` is invalid and will just be ignored',
+        path
       )
     } else {
-      return ast
+      return {
+        ast,
+        visitorKeys: keysFromParser(parserPath, parser, undefined),
+      }
     }
   }
 
-  return parser.parse(content, parserOptions)
+  const keys = keysFromParser(parserPath, parser, undefined)
+  return {
+    ast: parser.parse(content, parserOptions),
+    visitorKeys: keys,
+  }
 }
 
+
 function getParserPath(path, context) {
   const parsers = context.settings['import/parsers']
   if (parsers != null) {

utils/unambiguous.js

@@ -1,8 +1,7 @@
 'use strict'
 exports.__esModule = true
 
-
-const pattern = /(^|;)\s*(export|import)((\s+\w)|(\s*[{*=]))/m
+const pattern = /(^|;)\s*(export|import)((\s+\w)|(\s*[{*=]))|import\(/m
 /**
  * detect possible imports/exports without a full parse.
  *
@@ -26,5 +25,5 @@ const unambiguousNodeType = /^(?:(?:Exp|Imp)ort.*Declaration|TSExportAssignment)
  * @return {Boolean}
  */
 exports.isModule = function isUnambiguousModule(ast) {
-  return ast.body.some(node => unambiguousNodeType.test(node.type))
+  return ast.body && ast.body.some(node => unambiguousNodeType.test(node.type))
 }

utils/visit.js

@@ -0,0 +1,28 @@
+exports.__esModule = true
+
+exports.default = function visit(node, keys, visitorSpec) {
+  if (!node || !keys) {
+    return
+  }
+    const type = node.type
+    if (typeof visitorSpec[type] === 'function') {
+      visitorSpec[type](node)
+    }
+    const childFields = keys[type]
+    if (!childFields) {
+      return
+    }
+    for (const fieldName of childFields) {
+      const field = node[fieldName]
+      if (Array.isArray(field)) {
+        for (const item of field) {
+          visit(item, keys, visitorSpec)
+        }
+      } else {
+        visit(field, keys, visitorSpec)
+      }
+    }
+    if (typeof visitorSpec[`${type}:Exit`] === 'function') {
+      visitorSpec[`${type}:Exit`](node)
+    }
+}