feat(prefer-jest-mocked): add new rule (#1599)

Co-authored-by: s.v.zaytsev <[email protected]>
Co-authored-by: Gareth Jones <[email protected]>

Author: 3 people

README.md

@@ -355,6 +355,7 @@ Manually fixable by
 | [prefer-hooks-in-order](docs/rules/prefer-hooks-in-order.md)                 | Prefer having hooks in a consistent order                                 |     |     |     |     |
 | [prefer-hooks-on-top](docs/rules/prefer-hooks-on-top.md)                     | Suggest having hooks before any test cases                                |     |     |     |     |
 | [prefer-importing-jest-globals](docs/rules/prefer-importing-jest-globals.md) | Prefer importing Jest globals                                             |     |     | 🔧  |     |
+| [prefer-jest-mocked](docs/rules/prefer-jest-mocked.md)                       | Prefer `jest.mocked()` over `fn as jest.Mock`                             |     |     | 🔧  |     |
 | [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-snapshot-hint](docs/rules/prefer-snapshot-hint.md)                   | Prefer including a hint with external snapshots                           |     |     |     |     |

docs/rules/prefer-jest-mocked.md

@@ -0,0 +1,38 @@
+# Prefer `jest.mocked()` over `fn as jest.Mock` (`prefer-jest-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.
+
+Restricted types:
+
+- `jest.Mock`
+- `jest.MockedFunction`
+- `jest.MockedClass`
+- `jest.MockedObject`
+
+## 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

@@ -46,6 +46,7 @@ exports[`rules should export configs that refer to actual rules 1`] = `
       "jest/prefer-hooks-in-order": "error",
       "jest/prefer-hooks-on-top": "error",
       "jest/prefer-importing-jest-globals": "error",
+      "jest/prefer-jest-mocked": "error",
       "jest/prefer-lowercase-title": "error",
       "jest/prefer-mock-promise-shorthand": "error",
       "jest/prefer-snapshot-hint": "error",
@@ -128,6 +129,7 @@ exports[`rules should export configs that refer to actual rules 1`] = `
       "jest/prefer-hooks-in-order": "error",
       "jest/prefer-hooks-on-top": "error",
       "jest/prefer-importing-jest-globals": "error",
+      "jest/prefer-jest-mocked": "error",
       "jest/prefer-lowercase-title": "error",
       "jest/prefer-mock-promise-shorthand": "error",
       "jest/prefer-snapshot-hint": "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)