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LibJS: Implement Iterator.prototype.map

This uses a new Iterator type called IteratorHelper. This does not
implement IteratorHelper.prototype.return as that relies on generator
objects (i.e. the internal slots of JS::GeneratorObject), which are not
hooked up here.
This commit is contained in:
Timothy Flynn 2023-06-25 09:39:33 -04:00 committed by Andreas Kling
parent 7ff6b472c0
commit 3eb2e4e08a
10 changed files with 401 additions and 4 deletions

View file

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describe("errors", () => {
test("called with non-callable object", () => {
expect(() => {
Iterator.prototype.map(Symbol.hasInstance);
}).toThrowWithMessage(TypeError, "mapper is not a function");
});
test("iterator's next method throws", () => {
function TestError() {}
class TestIterator extends Iterator {
next() {
throw new TestError();
}
}
expect(() => {
const iterator = new TestIterator().map(() => 0);
iterator.next();
}).toThrow(TestError);
});
test("value returned by iterator's next method throws", () => {
function TestError() {}
class TestIterator extends Iterator {
next() {
return {
done: false,
get value() {
throw new TestError();
},
};
}
}
expect(() => {
const iterator = new TestIterator().map(() => 0);
iterator.next();
}).toThrow(TestError);
});
test("mapper function throws", () => {
function TestError() {}
class TestIterator extends Iterator {
next() {
return {
done: false,
value: 1,
};
}
}
expect(() => {
const iterator = new TestIterator().map(() => {
throw new TestError();
});
iterator.next();
}).toThrow(TestError);
});
});
describe("normal behavior", () => {
test("length is 1", () => {
expect(Iterator.prototype.map).toHaveLength(1);
});
test("mapper function sees every value", () => {
function* generator() {
yield "a";
yield "b";
}
let count = 0;
const iterator = generator().map((value, index) => {
++count;
switch (index) {
case 0:
expect(value).toBe("a");
break;
case 1:
expect(value).toBe("b");
break;
default:
expect().fail(`Unexpected mapper invocation: value=${value} index=${index}`);
break;
}
return value;
});
for (const i of iterator) {
}
expect(count).toBe(2);
});
test("mapper function can modify values", () => {
function* generator() {
yield "a";
yield "b";
}
const iterator = generator().map(value => value.toUpperCase());
let value = iterator.next();
expect(value.value).toBe("A");
expect(value.done).toBeFalse();
value = iterator.next();
expect(value.value).toBe("B");
expect(value.done).toBeFalse();
value = iterator.next();
expect(value.value).toBeUndefined();
expect(value.done).toBeTrue();
});
test("mappers can be chained", () => {
function* generator() {
yield 1;
yield 2;
}
const iterator = generator()
.map(value => value * 2)
.map(value => value + 10);
let value = iterator.next();
expect(value.value).toBe(12);
expect(value.done).toBeFalse();
value = iterator.next();
expect(value.value).toBe(14);
expect(value.done).toBeFalse();
value = iterator.next();
expect(value.value).toBeUndefined();
expect(value.done).toBeTrue();
});
});