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describe("[Call][GetOwnProperty]] trap normal behavior", () => {
test("forwarding when not defined in handler", () => {
expect(
Object.getOwnPropertyDescriptor(new Proxy({}, { getOwnPropertyDescriptor: null }), "a")
).toBeUndefined();
expect(
Object.getOwnPropertyDescriptor(
new Proxy({}, { getOwnPropertyDescriptor: undefined }),
"a"
)
).toBeUndefined();
expect(Object.getOwnPropertyDescriptor(new Proxy({}, {}), "a")).toBeUndefined();
});
test("correct arguments supplied to trap", () => {
let o = {};
let p = new Proxy(o, {
getOwnPropertyDescriptor(target, property) {
expect(target).toBe(o);
expect(property).toBe("foo");
},
});
Object.getOwnPropertyDescriptor(p, "foo");
});
test("conditional returned descriptor", () => {
let o = { foo: "bar" };
Object.defineProperty(o, "baz", {
value: "qux",
enumerable: false,
configurable: true,
writable: false,
});
let p = new Proxy(o, {
getOwnPropertyDescriptor(target, property) {
if (property === "baz") return Object.getOwnPropertyDescriptor(target, "baz");
return {
value: target[property],
enumerable: false,
configurable: true,
writable: true,
};
},
});
expect(p).toHaveConfigurableProperty("baz");
expect(p).not.toHaveEnumerableProperty("baz");
expect(p).not.toHaveWritableProperty("baz");
expect(p).toHaveValueProperty("baz", "qux");
expect(p).not.toHaveGetterProperty("baz");
expect(p).not.toHaveSetterProperty("baz");
d = Object.getOwnPropertyDescriptor(p, "foo");
expect(p).toHaveConfigurableProperty("foo");
expect(p).not.toHaveEnumerableProperty("foo");
expect(p).toHaveWritableProperty("foo");
expect(p).toHaveValueProperty("foo", "bar");
expect(p).not.toHaveGetterProperty("foo");
expect(p).not.toHaveSetterProperty("foo");
});
});
describe("[[GetOwnProperty]] invariants", () => {
test("must return an object or undefined", () => {
expect(() => {
Object.getOwnPropertyDescriptor(
new Proxy(
{},
{
getOwnPropertyDescriptor() {
return 1;
},
}
)
);
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: must return an object or undefined"
);
});
test("cannot return undefined for a non-configurable property", () => {
let o = {};
Object.defineProperty(o, "foo", { value: 10, configurable: false });
let p = new Proxy(o, {
getOwnPropertyDescriptor() {
return undefined;
},
});
expect(Object.getOwnPropertyDescriptor(p, "bar")).toBeUndefined();
expect(() => {
Object.getOwnPropertyDescriptor(p, "foo");
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: cannot return undefined for a property on the target which is a non-configurable property"
);
});
test("cannot return undefined for an existing property if the target is non-extensible", () => {
let o = {};
Object.defineProperty(o, "baz", {
value: 20,
configurable: true,
writable: true,
enumerable: true,
});
Object.preventExtensions(o);
let p = new Proxy(o, {
getOwnPropertyDescriptor() {
return undefined;
},
});
expect(() => {
Object.getOwnPropertyDescriptor(p, "baz");
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: cannot report a property as being undefined if it exists as an own property of the target and the target is non-extensible"
);
});
test("invalid property descriptors", () => {
let o = {};
Object.defineProperty(o, "v1", { value: 10, configurable: false });
Object.defineProperty(o, "v2", { value: 10, configurable: false, enumerable: true });
Object.defineProperty(o, "v3", {
configurable: false,
get() {
return 1;
},
});
Object.defineProperty(o, "v4", {
value: 10,
configurable: false,
writable: false,
enumerable: true,
});
expect(() => {
Object.getOwnPropertyDescriptor(
new Proxy(o, {
getOwnPropertyDescriptor() {
return { configurable: true };
},
}),
"v1"
);
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: invalid property descriptor for existing property on the target"
);
expect(() => {
Object.getOwnPropertyDescriptor(
new Proxy(o, {
getOwnPropertyDescriptor() {
return { enumerable: false };
},
}),
"v2"
);
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: invalid property descriptor for existing property on the target"
);
expect(() => {
Object.getOwnPropertyDescriptor(
new Proxy(o, {
getOwnPropertyDescriptor() {
return { value: 10 };
},
}),
"v3"
);
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: invalid property descriptor for existing property on the target"
);
expect(() => {
Object.getOwnPropertyDescriptor(
new Proxy(o, {
getOwnPropertyDescriptor() {
return { value: 10, writable: true };
},
}),
"v4"
);
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: invalid property descriptor for existing property on the target"
);
});
test("cannot report a property as non-configurable if it does not exist or is non-configurable", () => {
let o = {};
Object.defineProperty(o, "v", { configurable: true });
expect(() => {
Object.getOwnPropertyDescriptor(
new Proxy(o, {
getOwnPropertyDescriptor() {
return { configurable: false };
},
}),
"v"
);
}).toThrowWithMessage(
TypeError,
"Proxy handler's getOwnPropertyDescriptor trap violates invariant: cannot report target's property as non-configurable if the property does not exist, or if it is configurable"
);
});
});
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