JSTests/stress/change-attribute-structure-transition.js

function shouldBe(actual, expected) {
    if (actual !== expected)
        throw new Error('bad value: ' + actual);
}

var object = {
    test001: 42
};

Object.defineProperty(object, "test001", {
    writable: false
});

function sd(obj) {
    let data = $vm.getStructureTransitionList(obj)
    let result = []

    if (!data)
        return result

    function kind(kind)
    {
        switch (kind) {
        case 1:
            return "added"
        case 2:
            return "deleted"
        case 3:
            return "attribute"
        default:
            return "unknown";
        }
    }

    for (let i = 0; i < data.length/5; ++i) {
        result.push({ offset: data[i*5+1], max: data[i*5+2], property: data[i*5+3], type: kind(data[i*5+4]) })
    }

    return result
}

shouldBe(JSON.stringify(sd(object)), `[{"offset":-1,"max":-1,"property":null,"type":"unknown"},{"offset":0,"max":0,"property":"test001","type":"added"},{"offset":0,"max":0,"property":"test001","type":"attribute"}]`);

delete object.test001;
shouldBe(JSON.stringify(sd(object)), `[{"offset":-1,"max":-1,"property":null,"type":"unknown"},{"offset":0,"max":0,"property":"test001","type":"added"},{"offset":0,"max":0,"property":"test001","type":"attribute"},{"offset":0,"max":0,"property":"test001","type":"deleted"}]`);

function lastStructureID()
{
    var object = {
        test001: 42
    };
    Object.defineProperty(object, "test001", {
        writable: false
    });
    var list = $vm.getStructureTransitionList(object);
    return list[list.length - 5];
}

var structureID = lastStructureID();
shouldBe(structureID, lastStructureID()); // Transition is traced.

var object = {
    test001: 42
};
Object.defineProperty(object, "test001", {
    writable: false
});
// Make it Dictionary.
for (var i = 0; i < 1000; ++i)
    object["test" + i] = i;
shouldBe(object.test001, 42);
shouldBe(JSON.stringify(Object.getOwnPropertyDescriptor(object, "test001")), `{"value":42,"writable":false,"enumerable":true,"configurable":true}`);
Object.defineProperty(object, "test001", {
    enumerable: false
});
shouldBe(JSON.stringify(Object.getOwnPropertyDescriptor(object, "test001")), `{"value":42,"writable":false,"enumerable":false,"configurable":true}`);
shouldBe(JSON.stringify(sd(object)), `[{"offset":-1,"max":1098,"property":null,"type":"unknown"},{"offset":0,"max":1098,"property":"test001","type":"attribute"}]`);