append method in FormData won't accept File

[mumumilk]

Describe the bug

I'm trying to test a piece of code that includes appending a file to a FormData instance, similar to this:

import { assert, expect, test } from "vitest";

export const uploadFile = (data = { files: [] as File[] }): FormData => {
  const formData = new FormData();

  for (const file of data.files) {
    formData.append("file", file, file.name);
  }

  return formData;
};

test("should create a correct formdata", () => {
  const files = [new File([""], "filename", { type: "text/csv" })];
  const formdata = uploadFile({ files });

  expect(formdata.get("file")).toMatchObject(files[0]);
});

Although it works just fine running in Stackblitz, it fails to run locally using node and outputs the following error:

TypeError: Failed to execute 'append' on 'FormData': parameter 2 is not of type 'Blob'

I also tried to use String/Blob types since they are supported in the original FormData spec (according to MDN at least), but without success.

As per discord thread, it seems that node 18 has its own Blob/FormData and so Vitest wont override to use JSDOM polyfills for that.

vite.config.ts

export default defineConfig({
   test: {
     globals: true,
     environment: "jsdom",
   },
 });

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-pv9eck?file=test/basic.test.ts

System Info

System:
    OS: macOS 11.6
    CPU: (8) arm64 Apple M1
    Memory: 122.02 MB / 8.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 18.8.0 - ~/.nvm/versions/node/v18.8.0/bin/node
    Yarn: 1.22.15 - /usr/local/bin/yarn
    npm: 8.18.0 - ~/.nvm/versions/node/v18.8.0/bin/npm
  Browsers:
    Chrome: 107.0.5304.87
    Firefox: 106.0.2
    Safari: 15.2
  npmPackages:
    vitest: ^0.24.5 => 0.24.5

Used Package Manager

npm

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