TypedArrays Are not typed arrays at runtime

[richardspence]

🐛 Bug Report

Latest Jest destructively interferes with TypedArrays at runtime.

To Reproduce

Run this test on Jest 26.*. Reproduced on 26.6.3

test('foo', ()=>{
expect(new Uint8Array(4).buffer instanceof ArrayBuffer).toBe(true);
})

Impact

Not using the real types for typed arrays has trickle down affects like constructing DataViews (who reject input arguments that are not ArrayBuffers).

Expected behavior

The test should pass

Note: This test passes in jest 24.9.0 and 25.5.4

Link to repl or repo (highly encouraged)

Repro Link

envinfo

  System:
    OS: macOS Mojave 10.14.6
    CPU: (8) x64 Intel(R) Core(TM) i7-8559U CPU @ 2.70GHz
    Memory: 2.35 GB / 16.00 GB
    Shell: 5.3 - /bin/zsh
  Binaries:
    Node: 11.15.0 - ~/.nvm/versions/node/v11.15.0/bin/node
    Yarn: 1.12.1 - /usr/local/bin/yarn
    npm: 6.7.0 - ~/.nvm/versions/node/v11.15.0/bin/npm
  Managers:
    Homebrew: 2.4.8 - /usr/local/bin/brew
    pip3: 18.1 - /Library/Frameworks/Python.framework/Versions/3.7/bin/pip3
    RubyGems: 2.5.2.3 - /usr/bin/gem
  Utilities:
    Make: 3.81 - /usr/bin/make
    GCC: 4.2.1 - /usr/bin/gcc
    Git: 2.19.1 - /usr/local/bin/git
    Clang: 1100.0.33.17 - /usr/bin/clang
    Subversion: 1.10.4 - /usr/bin/svn
  Servers:
    Apache: 2.4.34 - /usr/sbin/apachectl
  Virtualization:
    Docker: 19.03.13 - /usr/local/bin/docker
  SDKs:
    iOS SDK:
      Platforms: iOS 13.2, DriverKit 19.0, macOS 10.15, tvOS 13.2, watchOS 6.1
  IDEs:
    Emacs: 22.1.1 - /usr/bin/emacs
    Nano: 2.0.6 - /usr/bin/nano
    VSCode: 1.51.1 - /usr/local/bin/code
    Vim: 8.0 - /usr/bin/vim
    Xcode: 11.3.1/11C504 - /usr/bin/xcodebuild
  Languages:
    Bash: 3.2.57 - /bin/bash
    Java: 11.0.1 - /usr/bin/javac
    Perl: 5.18.4 - /usr/bin/perl
    PHP: 7.1.23 - /usr/bin/php
    Python: 2.7.10 - /usr/bin/python
    Python3: 3.7.2 - /Library/Frameworks/Python.framework/Versions/3.7/bin/python3
    R: 4.0.0 - /usr/local/bin/R
    Ruby: 2.3.7 - /usr/bin/ruby
  Databases:
    SQLite: 3.24.0 - /usr/bin/sqlite3
  Browsers:
    Chrome: 86.0.4240.198
    Edge: 87.0.664.41
    Firefox: 74.0
    Safari: 13.0.1

[shartte]

Likely duplicate of #10786

We're running into the same problem since updating to CRA4 (and hence Jest 26). In our case, it's new Uint8Array(...).buffer instanceof ArrayBuffer being false.

@richardspence: Can you try removing this line locally and see if the test will run for you?
https://github.com/facebook/jest/blame/890852b18a6c863015d54e9fb2894ec57f546e1e/packages/jest-environment-jsdom/src/index.ts#L53

That did it for me. That line seems suspicious. If it copies ArrayBuffer, it should likely also copy the global Uint8Array, but doesn't. Additionally, in spite of what that comment says, after removing the line, window.ArrayBuffer is still available.

[Kuirak]

I got the same problem when using @peculiar/webcrypto as polyfill in jest.

Removing the line locally didn't fix it for me.

The only thing working for now is using jest-environment-jsdom@25 but it doesn't feel like a good solution.

[ExE-Boss]

As I said in #10786 (comment):

That’s because Jest uses a new VM context, and overrides the VM context’s ArrayBuffer with the top‑level global object’s ArrayBuffer, but doesn’t do this for typed arrays, which construct their ArrayBuffers using the overwritten ArrayBuffer constructor:

new Uint8Array().buffer.constructor !== ArrayBuffer;

Regressed by: #9606

[github-actions]

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