[new-rule] Force to use jest.mocked(fn) instead of fn as jest.Mock

[retyui]

Requirements:

• ts only
• Jest version 28+ only
• auto-fixable
• should cover as jest.MockedFunction type casting
• should cover as jest.Mock type casting
• should fix all the next examples

Examples:

// bad
const mockedUseFocused = useFocused as jest.MockedFunction<typeof useFocused>;
(AccessibilityInfo.isAccessibilityServiceEnabled as jest.Mock).mockResolvedValue(false);
const filter = (MessageService.getMessage as jest.Mock).mock.calls[0][0];
((getIsUserProfileFeatureSwitchEnabled as unknown) as jest.Mock).mockReturnValue(false);
((obj.obg2.obg3.obgN as jest.Mock).mockReturnValue(1);
((obj.myfn().myfn2 as jest.Mock).mockReturnValue('str');


// better
const mockedUseFocused = jest.mocked(useFocused)
jest.mocked(AccessibilityInfo.isAccessibilityServiceEnabled).mockResolvedValue(false);
const filter = jest.mocked(MessageService.getMessage).mock.calls[0][0];
jest.mocked(getIsUserProfileFeatureSwitchEnabled).mockReturnValue(false);
jest.mocked(obj.obg2.obg3.obgN).mockReturnValue(1);
jest.mocked(obj.myfn().myfn2).mockReturnValue('str');

Draft implementation

function unpackMemberExpression(node) {
  if (node.type === 'Identifier') {
    return node.name;
  }
  return `${unpackMemberExpression(node.object)}.${node.property.name}`;
}

function getFnName(node) {
  if (node.type === 'MemberExpression') {
    // case `Obj.myFn as jest.Mock`
    return unpackMemberExpression(node);
  }
  if (node.type === 'TSAsExpression') {
    // case: `myFn as unknown as jest.Mock`
    return getFnName(node.expression);
  }

  // case `myFn as jest.Mock`
  return node.name;
}

const mockTypes = ['MockedFunction', 'Mock'];

// Bad:
//   (myFn as jest.Mock)
//   myFn as jest.MockedFunction<typeof myFn>
// Good:
//   jest.mocked(myFn).mockReturnValue(...)
const noAsJestExpression = {
  meta: {
    type: 'suggestion',
    fixable: 'code',
    messages: {
      noAsJestExpression:
        'Please use jest api `jest.mocked({{fnName}})` instead of `{{fnName}} as jest.Mock`',
    },
  },
  create(context) {
    return {
      TSAsExpression(node) {
        const isJestMock =
          node?.typeAnnotation?.typeName?.left?.name === 'jest' &&
          mockTypes.includes(node?.typeAnnotation?.typeName?.right?.name);

        if (!isJestMock) {
          return;
        }

        const fnName = getFnName(node.expression);

        if (!fnName) {
          console.log(
            "[no-as-jest-expression]: Can't extracted fn name from expression:\n" +
              context.getSourceCode().getText(node)
          );
          return;
        }

        context.report({
          node,
          messageId: 'noAsJestExpression',
          data: {
            fnName,
          },
          fix(fixer) {
            return fixer.replaceText(node, `jest.mocked(${fnName})`);
          },
        });
      },
    };
  },
};

module.exports = noAsJestExpression;

[SimenB]

I like it - happy to take a PR 👍

[MillerSvt]

I'm working on it.

[github-actions]

🎉 This issue has been resolved in version 28.6.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀