delete an element in the array, patches is an empty array

[blinkcat]

🐛 Bug Report

immer v9.0.7
just delete an element in the array, it is not difficult to reproduce the bug, please take a look at the following demo or code.

Link to repro

demo

To Reproduce

import { produceWithPatches, enablePatches } from 'immer';

enablePatches();

const [newState, patches, inversePatches] = produceWithPatches(
  [1, 2, 3],
  (draft) => {
    delete draft[2];
  }
);

console.log(newState, patches, inversePatches);
// output:
// [1, 2, undefined] [] []

Observed behavior

As described above, patches and inversePatches are all empty

Expected behavior

They should not be empty.

Environment

We only accept bug reports against the latest Immer version.

• Immer version:
• I filed this report against the latest version of Immer
• Occurs with setUseProxies(true)
• Occurs with setUseProxies(false) (ES5 only)

[github-actions]

🎉 This issue has been resolved in version 9.0.11 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[bever1337]

Do I understand this prevents immer from creating sparse arrays with delete? I've spent the evening slowly removing pieces of my stack and API calls trying to find issues with sparse indices. I have no trouble creating sparse arrays using "proxied mutation"

// produces [<empty>,42]
(draftState: Draft<{ values: [] }>) => {
  values[1] = 42;
}

Then:

// produces [undefined, undefined]
// expected [<empty>, <empty>]
(draftState: Draft<{ values: [] }>) => {
  delete values[1];
}

[bever1337]

Be careful using the stackblitz console to test the reproduction results. It runs a parser on the input data which casts holes to undefined. Opening the browser's devtools reveals the proper output (no undefined values).