pool: vmThreads breaks source maps in tests

[sambev]

Describe the bug

When using vmThreads instead of threads (or the default), source maps seem to break while running the tests.

Small repro: https://github.com/sambev/vmthread-sourcemap-repro

With pool: 'threads', reporting works as expected

 FAIL  src/__tests__/sum.test.ts > sum
TypeError: Cannot set properties of undefined (setting 'name')
 ❯ Module.sum src/sum.ts:7:12
      5|
      6| export function sum(items: Item[]): number {
      7|   items[3].name = "break!";
       |            ^
      8|   return items.reduce((acc, item) => acc + item.count, 0);
      9| }
 ❯ src/__tests__/sum.test.ts:10:10

With pool: 'vmThreads', reporting is wrong:

  FAIL  src/__tests__/sum.test.ts > sum
TypeError: Cannot set properties of undefined (setting 'name')
 ❯ Module.sum src/sum.ts:2:17
      1| interface Item {
      2|   name: string;
       |                 ^
      3|   count: number;
      4| }
 ❯ src/__tests__/sum.test.ts:10:54

Reproduction

I have made a simple reproduction app based on the vanilla-ts vite template here:

https://github.com/sambev/vmthread-sourcemap-repro

All you should have to do is install deps (yarn install) and run tests (yarn test)

System Info

System:
    OS: macOS 14.3
    CPU: (8) arm64 Apple M1 Pro
    Memory: 86.81 MB / 16.00 GB
    Shell: 3.6.1 - /opt/homebrew/bin/fish
  Binaries:
    Node: 18.12.1 - ~/.volta/tools/image/node/18.12.1/bin/node
    Yarn: 1.22.19 - ~/.volta/tools/image/yarn/1.22.19/bin/yarn
    npm: 8.19.2 - ~/.volta/tools/image/node/18.12.1/bin/npm
  Browsers:
    Chrome: 121.0.6167.139
    Safari: 17.3
  npmPackages:
    vite: ^5.0.8 => 5.0.12
    vitest: ^1.2.2 => 1.2.2

Used Package Manager

yarn

Validations

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• Read the Contributing Guidelines.
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• The provided reproduction is a minimal reproducible example of the bug.

[hi-ogawa]

This is expected to be fixed by #5063 (it's not released yet but probably soon). The issue is previously reported in #5058 as inline snapshot bugs, but the underlying issue should be same.

I just updated the previous issue's title to mention source map, so it's easier for people to find a duplicate. Sorry about the confusion.