[esnext] prototype runtime implementation for async functions

test/mjsunit/harmony/async-await-basic.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-async-await
+
+function assertEqualsAsync(expected, run, msg) {
+    var actual;
+    var hadValue = false;
+    var hadError = false;
+    run().then(function(value) { hadValue = true; actual = value; },
+               function(error) { hadError = true; actual = error; });
+    flushMicrotasks();
+
+    if (hadError)
+        throw actual;
+    assertTrue(
+        hadValue, "Expected '" + run.toString() + "' to produce a value");
+
+    assertEquals(expected, actual, msg);
+}
+
+function assertThrowsAsync(run, errorType, message) {
+    let actual;
+    var hadError = false;
+    run().then(function(value) { actual = value; },
+               function(error) { hadError = true; actual = error; });
+    flushMicrotasks();
+
+    if (!hadError)
+        throw new Error(
+            "Expected " + run + "() to throw " + errorType.name +
+            ", but did not throw.");
+    if (!(actual instanceof errorType))
+        throw new Error(
+            "Expected " + run + "() to throw " + errorType.name +
+            ", but threw '" + actual + "'");
+    if (message !== void 0 && actual.message !== message)
+        throw new Error(
+            "Expected " + run + "() to throw '" + message + "', but threw '" +
+            actual.message + "'");
+}
+
+// TODO(caitp): give async functions a non-constructor map
+
+// Let F be ! FunctionAllocate(functionPrototype, Strict, "non-constructor")
+//async function asyncNonConstructorDecl() {}
+//assertThrows(
+//    () => new asyncNonConstructorDecl(), TypeError);
+//assertThrows(
+//    () => new (async function() {}), TypeError);
+//assertThrows(
+//    () => new ({ async nonConstructor() {} }).nonConstructor(), TypeError);
+//assertThrows(
+//    () => new (() => "not a constructor!"), TypeError);
+
+// Normal completion
+async function asyncDecl() { return "test"; }
+assertEqualsAsync("test", asyncDecl);
+assertEqualsAsync("test2", async function() { return "test2"; });
+
+// TODO(caitp): generate proper code for async arrows
+
+// assertEqualsAsync("test3", async () => "test3");
+// assertEqualsAsync("test4", () => ({ async f() { return "test4"; } }).f());
+
+class MyError extends Error {};
+
+// TODO(caitp): make catch handler lookup work correctly
+
+// Throw completion
+// async function asyncDeclThrower(e) { throw new MyError(e); }
+//assertThrowsAsync(
+//    () => asyncDeclThrower("boom!"), MyError, "boom!");
+//assertThrowsAsync(
+//    () => (async function(e) { throw new MyError(e); })("boom!!!"),
+//    MyError, "boom!!!");
+//assertThrowsAsync(
+//    () => (async e => { throw new MyError(e) })("boom!!"), MyError, "boom!!");
+//assertThrowsAsync(
+//    () => ({ async thrower(e) { throw new MyError(e); } }).thrower("boom!1!"),
+//    MyError, "boom!1!");
+
+function resolveLater(value) { return Promise.resolve(value); }
+function rejectLater(error) { return Promise.reject(error); }
+
+// Resume after Normal completion
+var log = [];
+async function resumeAfterNormal(value) {
+    log.push("start:" + value);
+    value = await resolveLater(value + 1);
+    log.push("resume:" + value);
+    value = await resolveLater(value + 1);
+    log.push("resume:" + value);
+    return value + 1;
+}
+
+assertEqualsAsync(4, () => resumeAfterNormal(1));
+assertEquals("start:1 resume:2 resume:3", log.join(" "));
+
+var O = {
+    async resumeAfterNormal(value) {
+        log.push("start:" + value);
+        value = await resolveLater(value + 1);
+        log.push("resume:" + value);
+        value = await resolveLater(value + 1);
+        log.push("resume:" + value);
+        return value + 1;
+    }
+};
+log = [];
+assertEqualsAsync(5, () => O.resumeAfterNormal(2));
+assertEquals("start:2 resume:3 resume:4", log.join(" "));
+
+// Resume after Throw completion
+async function resumeAfterThrow(value) {
+    log.push("start:" + value);
+    try {
+        value = await rejectLater("throw1");
+    } catch (e) {
+        log.push("resume:" + e);
+    }
+    try {
+        value = await rejectLater("throw2");
+    } catch (e) {
+        log.push("resume:" + e);
+    }
+    return value + 1;
+}
+
+log = [];
+assertEqualsAsync(2, () => resumeAfterThrow(1));
+assertEquals("start:1 resume:throw1 resume:throw2", log.join(" "));
+
+var O = {
+    async resumeAfterThrow(value) {
+        log.push("start:" + value);
+        try {
+            value = await rejectLater("throw1");
+        } catch (e) {
+            log.push("resume:" + e);
+        }
+        try {
+            value = await rejectLater("throw2");
+        } catch (e) {
+            log.push("resume:" + e);
+        }
+        return value + 1;
+    }
+}
+log = [];
+assertEqualsAsync(3, () => O.resumeAfterThrow(2));
+assertEquals("start:2 resume:throw1 resume:throw2", log.join(" "));