118 lines
3.7 KiB
JavaScript
118 lines
3.7 KiB
JavaScript
describe("[[Get]] trap normal behavior", () => {
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test("forwarding when not defined in handler", () => {
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expect(new Proxy({}, { get: undefined }).foo).toBeUndefined();
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expect(new Proxy({}, { get: null }).foo).toBeUndefined();
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expect(new Proxy({}, {}).foo).toBeUndefined();
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});
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test("correct arguments supplied to trap", () => {
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let o = {};
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let p = new Proxy(o, {
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get(target, property, receiver) {
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expect(target).toBe(o);
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expect(property).toBe("foo");
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expect(receiver).toBe(p);
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},
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});
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p.foo;
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});
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test("correct arguments passed to trap even for number", () => {
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let o = {};
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let p = new Proxy(o, {
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get(target, property, receiver) {
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expect(target).toBe(o);
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expect(property).toBe("1");
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expect(receiver).toBe(p);
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},
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});
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p[1];
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});
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test("conditional return", () => {
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let o = { foo: 1 };
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let p = new Proxy(o, {
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get(target, property, receiver) {
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if (property === "bar") {
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return 2;
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} else if (property === "baz") {
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return receiver.qux;
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} else if (property === "qux") {
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return 3;
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}
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return target[property];
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},
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});
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expect(p.foo).toBe(1);
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expect(p.bar).toBe(2);
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expect(p.baz).toBe(3);
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expect(p.qux).toBe(3);
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expect(p.test).toBeUndefined();
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expect(p[Symbol.hasInstance]).toBeUndefined();
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});
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test("custom receiver value", () => {
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let p = new Proxy(
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{},
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{
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get(target, property, receiver) {
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return receiver;
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},
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}
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);
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expect(Reflect.get(p, "foo", 42)).toBe(42);
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});
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});
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describe("[[Get]] invariants", () => {
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test("returned value must match the target property value if the property is non-configurable and non-writable", () => {
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let o = {};
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Object.defineProperty(o, "foo", { value: 5, configurable: false, writable: true });
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Object.defineProperty(o, "bar", { value: 10, configurable: false, writable: false });
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let p = new Proxy(o, {
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get() {
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return 8;
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},
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});
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expect(p.foo).toBe(8);
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expect(() => {
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p.bar;
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}).toThrowWithMessage(
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TypeError,
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"Proxy handler's get trap violates invariant: the returned value must match the value on the target if the property exists on the target as a non-writable, non-configurable own data property"
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);
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});
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test("returned value must be undefined if the property is a non-configurable accessor with no getter", () => {
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let o = {};
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Object.defineProperty(o, "foo", { configurable: false, set(_) {} });
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let p = new Proxy(o, {
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get() {
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return 8;
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},
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});
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expect(() => {
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p.foo;
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}).toThrowWithMessage(
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TypeError,
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"Proxy handler's get trap violates invariant: the returned value must be undefined if the property exists on the target as a non-configurable accessor property with an undefined get attribute"
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);
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});
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});
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test("Proxy handler that has the Proxy itself as its prototype", () => {
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const handler = {};
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const proxy = new Proxy({}, handler);
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handler.__proto__ = proxy;
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expect(() => {
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proxy.foo;
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}).toThrowWithMessage(InternalError, "Call stack size limit exceeded");
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});
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