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describe("parsing freestanding async functions", () => {
test("simple", () => {
expect(`async function foo() {}`).toEval();
// Although it does not create an async function it is valid.
expect(`async
function foo() {}`).toEval();
});
test("await expression", () => {
expect(`async function foo() { await bar(); }`).toEval();
expect(`async function foo() { await; }`).not.toEval();
expect(`function foo() { await bar(); }`).not.toEval();
expect(`function foo() { await; }`).toEval();
expect(`\\u0061sync function foo() { await bar(); }`).not.toEval();
expect(`\\u0061sync function foo() { \\u0061wait bar(); }`).not.toEval();
expect(`async function foo() { \\u0061wait bar(); }`).not.toEval();
});
});
describe("parsing object literal async functions", () => {
test("simple", () => {
expect(`x = { async foo() { } }`).toEval();
expect(`x = { async
foo() { } }`).not.toEval();
});
test("property on object called async", () => {
expect(`x = { async() { } }`).toEval();
expect(`x = { async() { await 4; } }`).not.toEval();
expect(`x = { async: 3 }`).toEval();
expect(`x = { async: await 3, }`).not.toEval();
});
test("await expression", () => {
expect(`x = { foo() { await bar(); } }`).not.toEval();
expect(`x = { foo() { await; } }`).toEval();
expect(`x = { async foo() { await bar(); } }`).toEval();
expect(`x = { async foo() { await; } }`).not.toEval();
});
});
describe("parsing classes with async methods", () => {
test("simple", () => {
expect(`class Foo { async foo() {} }`).toEval();
expect(`class Foo { static async foo() {} }`).toEval();
expect(`class Foo { async foo() { await bar(); } }`).toEval();
expect(`class Foo { async foo() { await; } }`).not.toEval();
expect(`class Foo { async constructor() {} }`).not.toEval();
});
});
test("function expression names equal to 'await'", () => {
expect(`async function foo() { (function await() {}); }`).toEval();
expect(`async function foo() { function await() {} }`).not.toEval();
});
test("async function cannot use await in default parameters", () => {
expect("async function foo(x = await 3) {}").not.toEval();
expect("async function foo(x = await 3) {}").not.toEval();
// Even as a reference to some variable it is not allowed
expect(`
var await = 4;
async function foo(x = await) {}
`).not.toEval();
});
describe("async arrow functions", () => {
test("basic syntax", () => {
expect("async () => await 3;").toEval();
expect("async param => await param();").toEval();
expect("async (param) => await param();").toEval();
expect("async (a, b) => await a();").toEval();
expect("async () => { await 3; }").toEval();
expect("async param => { await param(); }").toEval();
expect("async (param) => { await param(); }").toEval();
expect("async (a, b) => { await a(); }").toEval();
expect(`async
() => await 3;`).not.toEval();
expect("async async => await async()").toEval();
expect("async => async").toEval();
expect("async => await async()").not.toEval();
expect("async (b = await) => await b;").not.toEval();
expect("async (b = await 3) => await b;").not.toEval();
// Cannot escape the async keyword and get an async arrow function.
expect("\\u0061sync () => await 3").not.toEval();
expect("for (async of => {};false;) {}").toEval();
expect("for (async of []) {}").not.toEval();
expect("for (\\u0061sync of []) {}").toEval();
expect("for (\\u0061sync of => {};false;) {}").not.toEval();
expect("for (\\u0061sync => {};false;) {}").toEval();
});
test("async within a for-loop", () => {
let called = false;
// Unfortunately we cannot really test the more horrible case above.
for (
const f = async of => {
return of;
};
;
) {
expect(f(43)).toBeInstanceOf(Promise);
called = true;
break;
}
expect(called).toBeTrue();
});
});
test("basic functionality", () => {
test("simple", () => {
let executionValue = null;
let resultValue = null;
async function foo() {
executionValue = "someValue";
return "otherValue";
}
const returnValue = foo();
expect(returnValue).toBeInstanceOf(Promise);
returnValue.then(result => {
resultValue = result;
});
runQueuedPromiseJobs();
expect(executionValue).toBe("someValue");
expect(resultValue).toBe("otherValue");
});
test("await", () => {
let resultValue = null;
async function foo() {
return "someValue";
}
async function bar() {
resultValue = await foo();
}
bar();
runQueuedPromiseJobs();
expect(resultValue).toBe("someValue");
});
});
describe("non async function declaration usage of async still works", () => {
test("async as a function", () => {
function async(value = 4) {
return value;
}
expect(async(0)).toBe(0);
// We use eval here since it otherwise cannot find the async function.
const evalResult = eval("async(1)");
expect(evalResult).toBe(1);
});
test("async as a variable", () => {
let async = 3;
const evalResult = eval("async >= 2");
expect(evalResult).toBeTrue();
});
test("async with line ending does not create a function", () => {
expect(() => {
// The ignore is needed otherwise prettier puts a ';' after async.
// prettier-ignore
async
function f() {}
}).toThrowWithMessage(ReferenceError, "'async' is not defined");
expect(`async
function f() { await 3; }`).not.toEval();
});
});
describe("await cannot be used in class static init blocks", () => {
test("directly", () => {
expect("class A{ static { await; } }").not.toEval();
expect("class A{ static { let await = 3; } }").not.toEval();
expect("class A{ static { call(await); } }").not.toEval();
expect("class A{ static { for(const await = 1; false ;) {} } }").not.toEval();
});
test("via declaration", () => {
expect("class A{ static { class await {} } }").not.toEval();
expect("class A{ static { function await() {} } }").not.toEval();
expect("class A{ static { function* await() {} } }").not.toEval();
expect("class A{ static { async function* await() {} } }").not.toEval();
});
});
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