@swc/jest does not support jest mocking of exported functions within same module

[vikingair]

Describe the feature

Running this:

const swc = require('@swc/core');

const code = `
export const Func1 = () => 'test';
export const Func2 = () => Func1();
`;

swc.transform(code, {
    isModule: true,
    jsc: {
        target: 'es2019',
        parser: {
            syntax: 'typescript',
        },
        transform: {},
    },
    module: {
        type: 'commonjs',
    },
}).then((output) => {
    console.log(output.code);
});

Produces the following output:

"use strict";
Object.defineProperty(exports, "__esModule", {
    value: true
});
exports.Func2 = exports.Func1 = void 0;
const Func1 = ()=>'test'
;
exports.Func1 = Func1;
const Func2 = ()=>Func1()
;
exports.Func2 = Func2;

But then the following test code would not work:

import { Func2 } from './example';

jest.mock('./example', () => ({
  ...jest.requireActual('./example'),
  Func1: () => 'mocked',
});

it('should work', () => {
  expect(Func2()).toBe('mocked'); // but actually receiving here 'test'
});

When comparing the produced output to other Transformers, e.g. the following:

const sucrase = require('sucrase');

const code = `
export const Func1 = () => 'test';
export const Func2 = () => Func1();
`;

console.log(sucrase.transform(code, { transforms: ['jsx', 'typescript', 'imports'] }).code);

We get this output:

"use strict";Object.defineProperty(exports, "__esModule", {value: true});
 const Func1 = () => 'test'; exports.Func1 = Func1;
 const Func2 = () => exports.Func1.call(void 0, ); exports.Func2 = Func2;

Therefore I would suggest to change the implementation to use the exports object also when using exported functions inside other functions. E.g. the output fixing the above test should become:

"use strict";
Object.defineProperty(exports, "__esModule", {
    value: true
});
exports.Func2 = exports.Func1 = void 0;
const Func1 = ()=>'test'
;
exports.Func1 = Func1;
const Func2 = ()=>exports.Func1()
;
exports.Func2 = Func2;

Babel plugin or link to the feature description

No response

Additional context

No response

[kdy1]

Closing as duplicate. Please search first

[vikingair]

I guess you are referring to #4104? It is not always easy to find a matching issue within roughly 300 issues.

And actually I don't agree that this is the same issue.

[kdy1]

I meant #3843

[vikingair]

Thanks for sharing. Wasn't looking into the resolved issues.

To summarize here again:

This is expected behavior of swc and some other code transformers are wrong.

In order to fix it, stuff that needs to be mocked should be moved into separate modules.

[kdy1]

I don't think all other are wrong. I didn't say such sentence

[vikingair]

Ok. Sorry. I updated my comment to "some". But maybe I didn't fully get this one:

#3843 (comment)

And thanks for being so responsive. Made me consider to migrate our code base to swc instead of surcrase.

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.