[Bug]: Native fetch Arrays Incorrectly Matched

[popeeyy]

Version

v30.0.0-alpha.3 and v29.7.0

Steps to reproduce

1. Create a test file with this code

it('matches fetch parsed Array', async () => {
    expect(await (await fetch('https://avatar.roblox.com/v1/users/1/outfits')).json()).toMatchObject({
        data: expect.any(Array),
        filteredCount: expect.any(Number),
        total: expect.any(Number)
    })
})

it('matches manually parsed Array', async () => {
    expect(JSON.parse(await (await fetch('https://avatar.roblox.com/v1/users/1/outfits')).text())).toMatchObject({
        data: expect.any(Array),
        filteredCount: expect.any(Number),
        total: expect.any(Number)
    })
})

2. Run Jest

Expected behavior

Jest should identify the data property in the response body parsed by fetch as an Array.

Actual behavior

Jest does not identify the data property in the response body as an Array if it is parsed by fetch, only if it is parsed using JSON.parse.

Additional context

I am using the latest Node.js LTS version (v20.12.2)

Environment

System:
    OS: macOS 13.2.1
    CPU: (8) arm64 Apple M1 Pro
  Binaries:
    Node: 20.12.2 - /usr/local/bin/node
    npm: 10.5.0 - /usr/local/bin/npm
    pnpm: 7.30.3 - /usr/local/bin/pnpm
  npmPackages:
    jest: ^29.7.0 => 29.7.0

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[popeeyy]

Still an issue.

[SimenB]

This is #2549

You can probably use Array.from in your test code, that might help. Not sure there's much else we can do 🤔

We could fix the array case explicitly probably. Array.isArray works across realms

[SimenB]

Happy to take a PR fixing this for arrays

[popeeyy]

Happy to take a PR fixing this for arrays

Where in the code is the array matching? I attempted to look for it and fix the issue but the codebase is way too complex.

[SimenB]

jest/packages/expect/src/asymmetricMatchers.ts

Line 110 in 7bffeb5

asymmetricMatch(other: unknown) {

Add a new if (this.sample == Array) return Array.isArray(other). And maybe in getExpectedType()?