[Bug]: Jest runs out of memory when trying to print wide objects

[ryanwilsonperkin]

Version

27.5.1

Steps to reproduce

1. Clone my repo at /~https://github.com/ryanwilsonperkin/jest-issue-12364
2. yarn install
3. yarn test deep-array.test.js you should expect this to fail with an appropriate error message
4. yarn test wide-array.test.js you should expect this to crash

Expected behavior

I expect that when Jest has found that two objects don't match, and one of them is an array/objects with many (potentially deeply nested) elements, it should be able to print a message to the screen, even if it requires the array/object to be truncated.

This is currently the case for very deep elements, as shown by the deep-array.test.js test case, which simulates an infinitely deep array, and Jest correctly fails quickly with an error message that is limited in scope but does not try to print to infinity.

Actual behavior

Jest will run out of memory when trying to print wide arrays. Objects are passed to the pretty-format which has a maxDepth parameter to prevent printing very deep, but it does not have a maxWidth parameter (or similar) to prevent printing very wide.

This can be easily simulated with a test such as:

it('will crash', () => {
    const o = Array(1_000_000_000);
    expect(o).toBeNull();
});

Even though the runtime can very easily create an empty array of length 1 Billion, when we try to compare it against something, Jest will try to print the entire width of it.

This can also be an issue for objects that aren't extremely wide, but the combination of their widths at each depth result in the same. For example, a nested array that is 10 levels deep, but is 10 elements wide at each level contains 10^10 elements.

Additional context

No response

Environment

System:
    OS: macOS 12.2
    CPU: (8) arm64 Apple M1 Pro
  Binaries:
    Node: 17.2.0 - /opt/homebrew/bin/node
    Yarn: 1.22.17 - /opt/homebrew/bin/yarn
    npm: 8.1.4 - /opt/homebrew/bin/npm
  npmPackages:
    jest: 27.5.1 => 27.5.1

[SimenB]

Happy to take a PR that fixes this (either maxWidth like you suggest, or just make maxDepth impact the width as well) 👍

[ryanwilsonperkin]

Thanks @SimenB , I've opened #12402 to address this, let me know what you think

[SimenB]

/~https://github.com/facebook/jest/releases/tag/v28.0.0-alpha.2

[github-actions]

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