feat(prefer-mocked): add new rule (#1470)

README.md

@@ -352,6 +352,7 @@ set to warn in.\
 | [prefer-importing-jest-globals](docs/rules/prefer-importing-jest-globals.md) | Prefer importing Jest globals                                             |     |     | 🔧  |     |
 | [prefer-lowercase-title](docs/rules/prefer-lowercase-title.md)               | Enforce lowercase test names                                              |     |     | 🔧  |     |
 | [prefer-mock-promise-shorthand](docs/rules/prefer-mock-promise-shorthand.md) | Prefer mock resolved/rejected shorthands for promises                     |     |     | 🔧  |     |
+| [prefer-mocked](docs/rules/prefer-mocked.md)                                 | Prefer jest.mocked() over (fn as jest.Mock)                               |     |     | 🔧  |     |
 | [prefer-snapshot-hint](docs/rules/prefer-snapshot-hint.md)                   | Prefer including a hint with external snapshots                           |     |     |     |     |
 | [prefer-spy-on](docs/rules/prefer-spy-on.md)                                 | Suggest using `jest.spyOn()`                                              |     |     | 🔧  |     |
 | [prefer-strict-equal](docs/rules/prefer-strict-equal.md)                     | Suggest using `toStrictEqual()`                                           |     |     |     | 💡  |

docs/rules/prefer-mocked.md

@@ -0,0 +1,31 @@
+# Prefer jest.mocked() over (fn as jest.Mock) (`prefer-mocked`)
+
+🔧 This rule is automatically fixable by the
+[`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).
+
+<!-- end auto-generated rule header -->
+
+When working with mocks of functions using Jest, it's recommended to use the
+jest.mocked helper function to properly type the mocked functions. This rule
+enforces the use of jest.mocked for better type safety and readability.
+
+## Rule details
+
+The following patterns are warnings:
+
+```typescript
+(foo as jest.Mock).mockReturnValue(1);
+const mock = (foo as jest.Mock).mockReturnValue(1);
+(foo as unknown as jest.Mock).mockReturnValue(1);
+(Obj.foo as jest.Mock).mockReturnValue(1);
+([].foo as jest.Mock).mockReturnValue(1);
+```
+
+The following patterns are not warnings:
+
+```js
+jest.mocked(foo).mockReturnValue(1);
+const mock = jest.mocked(foo).mockReturnValue(1);
+jest.mocked(Obj.foo).mockReturnValue(1);
+jest.mocked([].foo).mockReturnValue(1);
+```

src/__tests__/__snapshots__/rules.test.ts.snap

@@ -48,6 +48,7 @@ exports[`rules should export configs that refer to actual rules 1`] = `
       "jest/prefer-importing-jest-globals": "error",
       "jest/prefer-lowercase-title": "error",
       "jest/prefer-mock-promise-shorthand": "error",
+      "jest/prefer-mocked": "error",
       "jest/prefer-snapshot-hint": "error",
       "jest/prefer-spy-on": "error",
       "jest/prefer-strict-equal": "error",
@@ -130,6 +131,7 @@ exports[`rules should export configs that refer to actual rules 1`] = `
       "jest/prefer-importing-jest-globals": "error",
       "jest/prefer-lowercase-title": "error",
       "jest/prefer-mock-promise-shorthand": "error",
+      "jest/prefer-mocked": "error",
       "jest/prefer-snapshot-hint": "error",
       "jest/prefer-spy-on": "error",
       "jest/prefer-strict-equal": "error",

src/__tests__/rules.test.ts

@@ -2,7 +2,7 @@ import { existsSync } from 'fs';
 import { resolve } from 'path';
 import plugin from '../';
 
-const numberOfRules = 53;
+const numberOfRules = 54;
 const ruleNames = Object.keys(plugin.rules);
 const deprecatedRules = Object.entries(plugin.rules)
   .filter(([, rule]) => rule.meta.deprecated)

src/rules/__tests__/prefer-mocked.test.ts

@@ -0,0 +1,321 @@
+import path from 'path';
+import dedent from 'dedent';
+import rule from '../prefer-mocked';
+import { FlatCompatRuleTester as RuleTester } from './test-utils';
+
+function getFixturesRootDir(): string {
+  return path.join(__dirname, 'fixtures');
+}
+
+const rootPath = getFixturesRootDir();
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('@typescript-eslint/parser'),
+  parserOptions: {
+    sourceType: 'module',
+    tsconfigRootDir: rootPath,
+    project: './tsconfig.json',
+  },
+});
+
+ruleTester.run('prefer-mocked', rule, {
+  valid: [
+    dedent`
+      import { foo } from './foo';
+      foo();
+    `,
+
+    dedent`
+      import { foo } from './foo';
+      jest.mocked(foo).mockReturnValue(1);
+    `,
+
+    dedent`
+      import { bar } from './bar';
+      bar.mockReturnValue(1);
+    `,
+
+    dedent`
+      import { foo } from './foo';
+      sinon.stub(foo).returns(1);
+    `,
+
+    dedent`
+      import { foo } from './foo';
+      foo.mockImplementation(() => 1);
+    `,
+
+    dedent`
+      const obj = { foo() {} };
+      obj.foo();
+    `,
+
+    dedent`
+      const mockFn = jest.fn();
+      mockFn.mockReturnValue(1);
+    `,
+
+    dedent`
+      const arr = [() => {}];
+      arr[0]();
+    `,
+
+    dedent`
+      const obj = { foo() {} };
+      obj.foo.mockReturnValue(1);
+    `,
+
+    dedent`
+      const obj = { foo() {} };
+      jest.spyOn(obj, 'foo').mockReturnValue(1);
+    `,
+
+    dedent`
+      type MockType = jest.Mock;
+      const mockFn = jest.fn();
+      (mockFn as MockType).mockReturnValue(1);
+    `,
+  ],
+  invalid: [
+    {
+      code: dedent`
+        import { foo } from './foo';
+        
+        (foo as jest.Mock).mockReturnValue(1);
+      `,
+      output: dedent`
+        import { foo } from './foo';
+        
+        (jest.mocked(foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { foo } from './foo';
+        
+        (foo as jest.Mock).mockImplementation(1);
+      `,
+      output: dedent`
+        import { foo } from './foo';
+        
+        (jest.mocked(foo)).mockImplementation(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { foo } from './foo';
+        
+        (foo as unknown as jest.Mock).mockReturnValue(1);
+      `,
+      output: dedent`
+        import { foo } from './foo';
+        
+        (jest.mocked(foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { Obj } from './foo';
+        
+        (Obj.foo as jest.Mock).mockReturnValue(1);
+      `,
+      output: dedent`
+        import { Obj } from './foo';
+        
+        (jest.mocked(Obj.foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        ([].foo as jest.Mock).mockReturnValue(1);
+      `,
+      output: dedent`
+        (jest.mocked([].foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 1,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { foo } from './foo';
+        
+        (foo as jest.MockedFunction).mockReturnValue(1);
+      `,
+      output: dedent`
+        import { foo } from './foo';
+        
+        (jest.mocked(foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { foo } from './foo';
+        
+        (foo as jest.MockedFunction).mockImplementation(1);
+      `,
+      output: dedent`
+        import { foo } from './foo';
+        
+        (jest.mocked(foo)).mockImplementation(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { foo } from './foo';
+        
+        (foo as unknown as jest.MockedFunction).mockReturnValue(1);
+      `,
+      output: dedent`
+        import { foo } from './foo';
+        
+        (jest.mocked(foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        import { Obj } from './foo';
+        
+        (Obj.foo as jest.MockedFunction).mockReturnValue(1);
+      `,
+      output: dedent`
+        import { Obj } from './foo';
+        
+        (jest.mocked(Obj.foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 3,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        (new Array(0).fill(null).foo as jest.MockedFunction).mockReturnValue(1);
+      `,
+      output: dedent`
+        (jest.mocked(new Array(0).fill(null).foo)).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 1,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        (jest.fn(() => foo) as jest.MockedFunction).mockReturnValue(1);
+      `,
+      output: dedent`
+        (jest.mocked(jest.fn(() => foo))).mockReturnValue(1);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 2,
+          line: 1,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        const mockedUseFocused = useFocused as jest.MockedFunction<typeof useFocused>;
+      `,
+      output: dedent`
+        const mockedUseFocused = jest.mocked(useFocused);
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 26,
+          line: 1,
+        },
+      ],
+    },
+    {
+      code: dedent`
+        const filter = (MessageService.getMessage as jest.Mock).mock.calls[0][0];
+      `,
+      output: dedent`
+        const filter = (jest.mocked(MessageService.getMessage)).mock.calls[0][0];
+      `,
+      options: [],
+      errors: [
+        {
+          messageId: 'useJestMocked',
+          column: 17,
+          line: 1,
+        },
+      ],
+    },
+  ],
+});