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fix Set iterator not reflecting mutations after creation #1691

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fix Set iterator not reflecting mutations after creation #1691

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a7c06f1
fix Set iterator not reflecting mutations after creation (#1671)
RealColdFry Mar 17, 2026
2bd60e8
Add tests for Set iterator mutation and exhaustion behavior
RealColdFry Mar 23, 2026
e52e216
Fix Map iterator mutation and add tests for mutation and exhaustion b…
RealColdFry Mar 23, 2026
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42 changes: 30 additions & 12 deletions src/lualib/Map.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -113,46 +113,64 @@ export class Map<K extends AnyNotNil, V> {
}

public entries(): IterableIterator<[K, V]> {
const getFirstKey = () => this.firstKey;
const { items, nextKey } = this;
let key = this.firstKey;
let key: K | undefined;
let started = false;
return {
[Symbol.iterator](): IterableIterator<[K, V]> {
return this;
},
next(): IteratorResult<[K, V]> {
const result = { done: !key, value: [key, items.get(key!)] as [K, V] };
key = nextKey.get(key!);
return result;
if (!started) {
started = true;
key = getFirstKey();
} else {
key = nextKey.get(key!);
}
return { done: !key, value: [key!, items.get(key!)] as [K, V] };
},
};
}

public keys(): IterableIterator<K> {
const getFirstKey = () => this.firstKey;
const nextKey = this.nextKey;
let key = this.firstKey;
let key: K | undefined;
let started = false;
return {
[Symbol.iterator](): IterableIterator<K> {
return this;
},
next(): IteratorResult<K> {
const result = { done: !key, value: key };
key = nextKey.get(key!);
return result as IteratorResult<K>;
if (!started) {
started = true;
key = getFirstKey();
} else {
key = nextKey.get(key!);
}
return { done: !key, value: key! };
},
};
}

public values(): IterableIterator<V> {
const getFirstKey = () => this.firstKey;
const { items, nextKey } = this;
let key = this.firstKey;
let key: K | undefined;
let started = false;
return {
[Symbol.iterator](): IterableIterator<V> {
return this;
},
next(): IteratorResult<V> {
const result = { done: !key, value: items.get(key!) };
key = nextKey.get(key!);
return result;
if (!started) {
started = true;
key = getFirstKey();
} else {
key = nextKey.get(key!);
}
return { done: !key, value: items.get(key!) };
},
};
}
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42 changes: 30 additions & 12 deletions src/lualib/Set.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -102,46 +102,64 @@ export class Set<T extends AnyNotNil> {
}

public entries(): IterableIterator<[T, T]> {
const getFirstKey = () => this.firstKey;
const nextKey = this.nextKey;
let key: T = this.firstKey!;
let key: T | undefined;
let started = false;
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@Perryvw Perryvw Mar 22, 2026

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why add another bool instead of simply checking if key is undefined?

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@RealColdFry RealColdFry Mar 23, 2026

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key can also become undefined if the iterator is exhausted. if the iterator is then next'ed again, it will reset and get the first key

return {
[Symbol.iterator](): IterableIterator<[T, T]> {
return this;
},
next(): IteratorResult<[T, T]> {
const result = { done: !key, value: [key, key] as [T, T] };
key = nextKey.get(key);
return result;
if (!started) {
started = true;
key = getFirstKey();
} else {
key = nextKey.get(key!);
}
return { done: !key, value: [key!, key!] as [T, T] };
},
};
}

public keys(): IterableIterator<T> {
const getFirstKey = () => this.firstKey;
const nextKey = this.nextKey;
let key: T = this.firstKey!;
let key: T | undefined;
let started = false;
return {
[Symbol.iterator](): IterableIterator<T> {
return this;
},
next(): IteratorResult<T> {
const result = { done: !key, value: key };
key = nextKey.get(key);
return result;
if (!started) {
started = true;
key = getFirstKey();
} else {
key = nextKey.get(key!);
}
return { done: !key, value: key! };
},
};
}

public values(): IterableIterator<T> {
const getFirstKey = () => this.firstKey;
const nextKey = this.nextKey;
let key: T = this.firstKey!;
let key: T | undefined;
let started = false;
return {
[Symbol.iterator](): IterableIterator<T> {
return this;
},
next(): IteratorResult<T> {
const result = { done: !key, value: key };
key = nextKey.get(key);
return result;
if (!started) {
started = true;
key = getFirstKey();
} else {
key = nextKey.get(key!);
}
return { done: !key, value: key! };
},
};
}
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38 changes: 38 additions & 0 deletions test/unit/builtins/map.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -210,6 +210,44 @@ describe.each(iterationMethods)("map.%s() preserves insertion order", iterationM
});
});

describe.each(iterationMethods)("map.%s() handles mutation", iterationMethod => {
test("iterator persists after delete", () => {
util.testFunction`
const map = new Map<number, string>([[1, "a"], [2, "b"]]);
const iter = map.${iterationMethod}();
map.delete(1);
return iter.next().value;
`.expectToMatchJsResult();
});

test("iterator with delete and add between iterations", () => {
util.testFunction`
const map = new Map<number, string>([[1, "a"], [2, "b"], [3, "c"]]);
const iter = map.${iterationMethod}();
iter.next(); // 1
map.delete(2);
map.set(4, "d");
const results: IteratorResult<any>[] = [];
let r = iter.next();
while (!r.done) { results.push({ done: r.done, value: r.value }); r = iter.next(); }
return results;
`.expectToMatchJsResult();
});

test("iterator does not restart after exhaustion", () => {
util.testFunction`
const map = new Map<number, string>([[1, "a"], [2, "b"]]);
const iter = map.${iterationMethod}();
const results: boolean[] = [];
results.push(iter.next().done!);
results.push(iter.next().done!);
results.push(iter.next().done!); // should be done
results.push(iter.next().done!); // should still be done, not restart
return results;
`.expectToMatchJsResult();
});
});

describe("Map.groupBy", () => {
test("empty", () => {
util.testFunction`
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42 changes: 42 additions & 0 deletions test/unit/builtins/set.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -195,6 +195,48 @@ describe.each(iterationMethods)("set.%s() preserves insertion order", iterationM
});
});

describe.each(iterationMethods)("set.%s() handles mutation", iterationMethod => {
test("iterator persists after delete", () => {
util.testFunction`
const set1 = new Set<string | number>();
set1.add(42);
set1.add("forty two");

const iterator1 = set1.${iterationMethod}();
set1.delete(42);

return iterator1.next().value;
`.expectToMatchJsResult();
});

test("iterator with delete and add between iterations", () => {
util.testFunction`
const set = new Set([1, 2, 3]);
const iter = set.${iterationMethod}();
iter.next(); // 1
set.delete(2);
set.add(4);
const results: IteratorResult<any>[] = [];
let r = iter.next();
while (!r.done) { results.push({ done: r.done, value: r.value }); r = iter.next(); }
return results;
`.expectToMatchJsResult();
});

test("iterator does not restart after exhaustion", () => {
util.testFunction`
const set = new Set([1, 2]);
const iter = set.${iterationMethod}();
const results: boolean[] = [];
results.push(iter.next().done!);
results.push(iter.next().done!);
results.push(iter.next().done!); // should be done
results.push(iter.next().done!); // should still be done, not restart
return results;
`.expectToMatchJsResult();
});
});

test("instanceof Set without creating set", () => {
util.testFunction`
const myset = 3 as any;
Expand Down