toMatchObject(): Error: [vitest] No "Symbol(Symbol.toStringTag)" export is defined

[yuliankarapetkov]

Describe the bug

I am mocking a module:

vi.mock("country-region-data", () => {
    return {
        allCountries: ["UK"],
        UK: "UK",
    }
})

Then, testing it:

// getCountries just imports the module - import("country-region-data")
const result = await getCountries()

expect(result).toMatchObject({
  allCountries: ["UK"],
  UK: "UK",
})

When I run the test, I get the following error:

Error: [vitest] No "Symbol(Symbol.iterator)" export is defined on the "country-region-data" mock. 
Did you forget to return it from "vi.mock"?

If I spread the object in expect (expect({ ...result })), the test succeeds.

I think it shouldn't expect an iterator in this case.

Reproduction

https://stackblitz.com/edit/node-pnfxmw?file=test%2Fcountries.test.ts,package.json

System Info

System:
    OS: macOS 13.1
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 1.06 GB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 19.2.0 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 8.13.1 - 
  Browsers:
    Brave Browser: 110.1.48.158
    Chrome: 109.0.5414.119
    Firefox: 105.0.1
    Safari: 16.2
  npmPackages:
    vite: ^4.1.1 => 4.1.1 
    vitest: ^0.28.4 => 0.28.4

Used Package Manager

npm

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