Iterating over a Set can cause mutations to be ignored

[matchu]

🐛 Bug Report

It seems that iterating over Immer's draft of a Set can cause mutations to be ignored. This seems to only happen when you iterate over the set before performing any mutations.

Link to repro

Here's a runnable code sample: https://runkit.com/matchu/5ea3a4b828ff10001bb538ea

const {produce, enableMapSet} = require("immer");
const {expect} = require("chai");

enableMapSet();

let set = new Set([1, 2]);
expect(Array.from(set).sort()).to.eql([1, 2]);

// If we just add to the set, it works!
set = produce(set, draftSet => {
    draftSet.add(3);
});
expect(Array.from(set).sort()).to.eql([1, 2, 3]);

// And we can safely iterate over the set between changes,
// and changes before and after will be applied correctly.
set = produce(set, draftSet => {
    draftSet.add(4);
    console.log("By the way, the set is ", Array.from(draftSet));
    draftSet.add(5);
});
expect(Array.from(set).sort()).to.eql([1, 2, 3, 4, 5]);

// But if we iterate over the set *before* making any changes,
// then all of our changes are ignored.
//
// This test case fails in Immer 6.0.3.
set = produce(set, draftSet => {
    console.log("By the way, the set is ", Array.from(draftSet));
    draftSet.add(6);
});
expect(Array.from(set).sort()).to.eql([1, 2, 3, 4, 5, 6]);

console.log("Done!");

To Reproduce

1. Enable Immer's MapSet plugin.
2. Use a produce function over the Set, which iterates over the content of the draft set and then mutates it.

Observed behavior

Mutations made to the draft Set during produce are not reflected in its return value.

Expected behavior

Mutations made to the draft Set during produce would be reflected in its return value, just as if I had not performed iteration before attempting mutation.

Environment

• Immer version: 6.0.3
• Occurs with setUseProxies(true)
• Occurs with setUseProxies(false) (ES5 only)

[matchu]

For now I'm going to work around this by adding a fake mutation near the start of my producer:

draftSet.add("fake-value-immer#586").delete("fake-value-immer#586");

[mweststrate]

Confirmed, thanks for the extensive report!

[aleclarson]

🎉 This issue has been resolved in version 6.0.7 🎉

The release is available on:

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

Your semantic-release bot 📦🚀

[matchu]

Thank you!!

[aleclarson]

🎉 This issue has been resolved in version 7.0.0 🎉

The release is available on:

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

Your semantic-release bot 📦🚀