typescript-eslint · abrahamguo · Sep 19, 2024 · Sep 19, 2024 · Oct 4, 2024 · Oct 4, 2024
diff --git a/packages/eslint-plugin/docs/rules/no-misused-object-likes.mdx b/packages/eslint-plugin/docs/rules/no-misused-object-likes.mdx
@@ -0,0 +1,34 @@
+---
+description: 'Disallow using `Object.{assign|entries|hasOwn|keys|values}(...)` and the `in` operator on Map/Set objects.'
+---
+
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+> 🛑 This file is source code, not the primary documentation location! 🛑
+>
+> See **https://typescript-eslint.io/rules/no-misused-object-likes** for documentation.
+
+Methods like `Object.assign()`, `Object.entries()`, `Object.hasOwn()`, `Object.keys()`, and `Object.values()` can be
+used work with collections of data stored in objects. However, when working with `Map` or `Set` objects, even though
+they are collections, using these methods are a mistake because they do not properly write to (in the case of
+`Object.assign()`) or read from the object.
+
+This rule prevents such methods from being used on `Map` and `Set` objects.
+
+<Tabs>
+  <TabItem value="❌ Incorrect">
+		```ts
+			console.log(Object.values(new Set('abc')));
+			Object.assign(new Map(), { k: 'v' });
+		```
+	</TabItem>
+  <TabItem value="✅ Correct">
+		```ts
+			console.log([...new Set('abc').values()]);
+			new Map().set('k', 'v');
+		```
+	</TabItem>
+</Tabs>
+
+{/* Intentionally Omitted: When Not To Use It */}
diff --git a/packages/eslint-plugin/src/configs/all.ts b/packages/eslint-plugin/src/configs/all.ts
@@ -73,6 +73,7 @@ export = {
     '@typescript-eslint/no-magic-numbers': 'error',
     '@typescript-eslint/no-meaningless-void-operator': 'error',
     '@typescript-eslint/no-misused-new': 'error',
+    '@typescript-eslint/no-misused-object-likes': 'error',
     '@typescript-eslint/no-misused-promises': 'error',
     '@typescript-eslint/no-mixed-enums': 'error',
     '@typescript-eslint/no-namespace': 'error',

diff --git a/packages/eslint-plugin/src/configs/disable-type-checked.ts b/packages/eslint-plugin/src/configs/disable-type-checked.ts
@@ -24,6 +24,7 @@ export = {
     '@typescript-eslint/no-for-in-array': 'off',
     '@typescript-eslint/no-implied-eval': 'off',
     '@typescript-eslint/no-meaningless-void-operator': 'off',
+    '@typescript-eslint/no-misused-object-likes': 'off',
     '@typescript-eslint/no-misused-promises': 'off',
     '@typescript-eslint/no-mixed-enums': 'off',
     '@typescript-eslint/no-redundant-type-constituents': 'off',

diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
@@ -52,6 +52,7 @@ import noLossOfPrecision from './no-loss-of-precision';
 import noMagicNumbers from './no-magic-numbers';
 import noMeaninglessVoidOperator from './no-meaningless-void-operator';
 import noMisusedNew from './no-misused-new';
+import noMisusedObjectLikes from './no-misused-object-likes';
 import noMisusedPromises from './no-misused-promises';
 import noMixedEnums from './no-mixed-enums';
 import noNamespace from './no-namespace';
@@ -181,6 +182,7 @@ const rules = {
   'no-magic-numbers': noMagicNumbers,
   'no-meaningless-void-operator': noMeaninglessVoidOperator,
   'no-misused-new': noMisusedNew,
+  'no-misused-object-likes': noMisusedObjectLikes,
   'no-misused-promises': noMisusedPromises,
   'no-mixed-enums': noMixedEnums,
   'no-namespace': noNamespace,

diff --git a/packages/eslint-plugin/src/rules/no-misused-object-likes.ts b/packages/eslint-plugin/src/rules/no-misused-object-likes.ts
@@ -0,0 +1,80 @@
+import type { TSESTree } from '@typescript-eslint/utils';
+import type * as ts from 'typescript';
+
+import { isSymbolFromDefaultLibrary } from '@typescript-eslint/type-utils';
+import { AST_NODE_TYPES } from '@typescript-eslint/utils';
+
+import {
+  createRule,
+  getParserServices,
+  getStaticMemberAccessValue,
+} from '../util';
+
+const METHODS = ['assign', 'entries', 'hasOwn', 'keys', 'values'];
+
+export default createRule({
+  name: 'no-misused-object-likes',
+  meta: {
+    type: 'problem',
+    docs: {
+      description: `Disallow using \`Object.{${METHODS.join(`|`)}}(...)\` and the \`in\` operator on Map/Set objects`,
+      requiresTypeChecking: true,
+    },
+    messages: {
+      misusedObjectLike:
+        "Don't use {{used}} on {{objectClass}} objects — it will not properly check the contents.",
+    },
+    schema: [],
+  },
+  defaultOptions: [],
+
+  create(context) {
+    const getSymbolIfFromDefaultLibrary = (
+      node: TSESTree.Node,
+    ): ts.Symbol | undefined => {
+      const services = getParserServices(context);
+      const symbol = services.getTypeAtLocation(node).getSymbol();
+      return isSymbolFromDefaultLibrary(services.program, symbol)
+        ? symbol
+        : undefined;
+    };
+    const checkClassAndReport = (node: TSESTree.Node, used: string): void => {
+      const objectClass = getSymbolIfFromDefaultLibrary(node)?.name;
+      if (objectClass && /^(Readonly|Weak)?(Map|Set)$/.test(objectClass)) {
+        context.report({
+          node,
+          messageId: 'misusedObjectLike',
+          data: { objectClass, used },
+        });
+      }
+    };
+    return {
+      BinaryExpression(node): void {
+        if (node.operator === 'in') {
+          checkClassAndReport(node.right, 'the `in` operator');
+        }
+      },
+      CallExpression(node): void {
+        const { arguments: args, callee } = node;
+        if (
+          args.length !== 1 ||
+          callee.type !== AST_NODE_TYPES.MemberExpression
+        ) {
+          return;
+        }
+        const { object } = callee;
+        if (
+          object.type !== AST_NODE_TYPES.Identifier ||
+          object.name !== 'Object' ||
+          getSymbolIfFromDefaultLibrary(object)
+        ) {
+          return;
+        }
+        const method = getStaticMemberAccessValue(callee, context);
+        if (typeof method === 'string' && METHODS.includes(method)) {
+          checkClassAndReport(args[0], `\`Object.${method}()\``);
+        }
+      },
+    };
+  },
+});
diff --git a/packages/eslint-plugin/tests/docs-eslint-output-snapshots/no-misused-object-likes.shot b/packages/eslint-plugin/tests/docs-eslint-output-snapshots/no-misused-object-likes.shot
diff --git a/packages/eslint-plugin/tests/rules/no-misused-object-likes.test.ts b/packages/eslint-plugin/tests/rules/no-misused-object-likes.test.ts
@@ -0,0 +1,120 @@
+import { RuleTester } from '@typescript-eslint/rule-tester';
+
+import rule from '../../src/rules/no-misused-object-likes';
+import { getFixturesRootDir } from '../RuleTester';
+
+const rootPath = getFixturesRootDir();
+
+const ruleTester = new RuleTester({
+  languageOptions: {
+    parserOptions: {
+      project: './tsconfig.json',
+      tsconfigRootDir: rootPath,
+    },
+  },
+});
+
+ruleTester.run('no-misused-object-likes', rule, {
+  valid: [
+    `
+      class ExMap extends Map {}
+      const map = new ExMap();
+      Object.keys(map);
+    `,
+    `
+      class ExMap extends Map {}
+      const map = new ExMap();
+      Object.values(map);
+    `,
+    `
+      class ExMap extends Map {}
+      const map = new ExMap();
+      Object.entries(map);
+    `,
+    `
+      const test = {};
+      Object.entries(test);
+    `,
+    `
+      const test = {};
+      Object.keys(test);
+    `,
+    `
+      const test = {};
+      Object.values(test);
+    `,
+    `
+      const test = [];
+      Object.keys(test);
+    `,
+    `
+      const test = [];
+      Object.values(test);
+    `,
+    `
+      const test = [];
+      Object.entries(test);
+    `,
+    `
+      const test = 123;
+      Object.keys(test);
+    `,
+    'Object.values(new (class Map {})());',
+    `
+      const Object = { keys: () => {} };
+      Object.keys(new Map());
+    `,
+  ],
+  invalid: [
+    {
+      code: `
+        const map = new Map();
+        const result = Object.keys(map);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    {
+      code: `
+        const map = new Map();
+        const result = Object.entries(map);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    {
+      code: `
+        const map = new Map();
+        const result = Object.values(map);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    {
+      code: `
+        const set = new Set();
+        const result = Object.keys(set);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    {
+      code: `
+        const set = new Set();
+        const result = Object.entries(set);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    {
+      code: `
+        const set = new Set();
+        const result = Object.values(set);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    {
+      code: `
+        const test = new WeakMap();
+        Object.keys(test);
+      `,
+      errors: [{ messageId: 'misusedObjectLike' }],
+    },
+    { code: '4 in new Set();', errors: [{ messageId: 'misusedObjectLike' }] },
+  ],
+});
diff --git a/packages/eslint-plugin/tests/schema-snapshots/no-misused-object-likes.shot b/packages/eslint-plugin/tests/schema-snapshots/no-misused-object-likes.shot
diff --git a/packages/typescript-eslint/src/configs/all.ts b/packages/typescript-eslint/src/configs/all.ts
@@ -86,6 +86,7 @@ export default (
       '@typescript-eslint/no-magic-numbers': 'error',
       '@typescript-eslint/no-meaningless-void-operator': 'error',
       '@typescript-eslint/no-misused-new': 'error',
+      '@typescript-eslint/no-misused-object-likes': 'error',
       '@typescript-eslint/no-misused-promises': 'error',
       '@typescript-eslint/no-mixed-enums': 'error',
       '@typescript-eslint/no-namespace': 'error',

diff --git a/packages/typescript-eslint/src/configs/disable-type-checked.ts b/packages/typescript-eslint/src/configs/disable-type-checked.ts
@@ -31,6 +31,7 @@ export default (
     '@typescript-eslint/no-for-in-array': 'off',
     '@typescript-eslint/no-implied-eval': 'off',
     '@typescript-eslint/no-meaningless-void-operator': 'off',
+    '@typescript-eslint/no-misused-object-likes': 'off',
     '@typescript-eslint/no-misused-promises': 'off',
     '@typescript-eslint/no-mixed-enums': 'off',
     '@typescript-eslint/no-redundant-type-constituents': 'off',