Adds NewPromiseCapability abstract operation (#43)

This PR introduces the `NewPromiseCapability` abstract operation. As
part of this, it uses the new abstract operation in the
`Promise.withResolvers` polyfill.

polyfills/Promise/withResolvers/config.toml

@@ -2,7 +2,7 @@ aliases = [ "es2024" ]
 dependencies = [
 	"_ESAbstract.CreateDataPropertyOrThrow",
 	"_ESAbstract.CreateMethodProperty",
-	"_ESAbstract.IsConstructor",
+	"_ESAbstract.NewPromiseCapability",
 	"Promise",
 ]
 license = "MIT"

polyfills/Promise/withResolvers/polyfill.js

@@ -1,18 +1,11 @@
-/* global CreateDataPropertyOrThrow, CreateMethodProperty, IsConstructor, Promise */
+/* global CreateDataPropertyOrThrow, CreateMethodProperty, NewPromiseCapability, Promise */
 (function () {
 	// 27.2.4.8 Promise.withResolvers ( )
 	CreateMethodProperty(Promise, "withResolvers", function withResolvers() {
 		// 1. Let C be the this value.
 		var C = this;
 		// 2. Let promiseCapability be ? NewPromiseCapability(C).
-		if (IsConstructor(C) === false) {
-			throw new TypeError("The `this` value must be a constructor");
-		}
-		var promiseCapability = {};
-		promiseCapability["[[Promise]]"] = new C(function (resolve, reject) {
-			promiseCapability["[[Resolve]]"] = resolve;
-			promiseCapability["[[Reject]]"] = reject;
-		});
+		var promiseCapability = NewPromiseCapability(C);
 		// 3. Let obj be OrdinaryObjectCreate(%Object.prototype%).
 		var obj = {};
 		// 4. Perform ! CreateDataPropertyOrThrow(obj, "promise", promiseCapability.[[Promise]]).

polyfills/_ESAbstract/NewPromiseCapability/config.toml

@@ -0,0 +1,23 @@
+dependencies = [
+	"_ESAbstract.Construct",
+	"_ESAbstract.IsCallable",
+	"_ESAbstract.IsConstructor",
+]
+spec = "https://tc39.es/ecma262/#sec-newpromisecapability"
+
+[browsers]
+android = "*"
+bb = "*"
+chrome = "*"
+edge = "*"
+edge_mob = "*"
+firefox = "*"
+firefox_mob = "*"
+ie = "*"
+ie_mob = "*"
+opera = "*"
+op_mob = "*"
+op_mini = "*"
+safari = "*"
+ios_saf = "*"
+samsung_mob = "*"

polyfills/_ESAbstract/NewPromiseCapability/polyfill.js

@@ -0,0 +1,48 @@
+/* global Construct, IsCallable, IsConstructor */
+// 27.2.1.5 NewPromiseCapability ( C )
+// eslint-disable-next-line no-unused-vars
+function NewPromiseCapability(C) {
+	// 1. If IsConstructor(C) is false, throw a TypeError exception.
+	if (IsConstructor(C) === false) {
+		throw new TypeError("C must be a constructor");
+	}
+	// 2. NOTE: C is assumed to be a constructor function that supports the parameter conventions of the Promise constructor (see 27.2.3.1).
+	// 3. Let resolvingFunctions be the Record { [[Resolve]]: undefined, [[Reject]]: undefined }.
+	var resolvingFunctions = {
+		"[[Resolve]]": undefined,
+		"[[Reject]]": undefined
+	};
+	// 4. Let executorClosure be a new Abstract Closure with parameters (resolve, reject) that captures resolvingFunctions and performs the following steps when called:
+	// 5. Let executor be CreateBuiltinFunction(executorClosure, 2, "", « »).
+	var executor = function (resolve, reject) {
+		// a. If resolvingFunctions.[[Resolve]] is not undefined, throw a TypeError exception.
+		if (resolvingFunctions["[[Resolve]]"] !== undefined) {
+			throw new TypeError("[[Resolve]] is not undefined");
+		}
+		// b. If resolvingFunctions.[[Reject]] is not undefined, throw a TypeError exception.
+		if (resolvingFunctions["[[Reject]]"] !== undefined) {
+			throw new TypeError("[[Reject]] is not undefined");
+		}
+		// c. Set resolvingFunctions.[[Resolve]] to resolve.
+		resolvingFunctions["[[Resolve]]"] = resolve;
+		// d. Set resolvingFunctions.[[Reject]] to reject.
+		resolvingFunctions["[[Reject]]"] = reject;
+		// e. Return undefined.
+	};
+	// 6. Let promise be ? Construct(C, « executor »).
+	var promise = Construct(C, [executor]);
+	// 7. If IsCallable(resolvingFunctions.[[Resolve]]) is false, throw a TypeError exception.
+	if (IsCallable(resolvingFunctions["[[Resolve]]"]) === false) {
+		throw new TypeError("[[Resolve]] is not callable");
+	}
+	// 8. If IsCallable(resolvingFunctions.[[Reject]]) is false, throw a TypeError exception.
+	if (IsCallable(resolvingFunctions["[[Reject]]"]) === false) {
+		throw new TypeError("[[Reject]] is not callable");
+	}
+	// 9. Return the PromiseCapability Record { [[Promise]]: promise, [[Resolve]]: resolvingFunctions.[[Resolve]], [[Reject]]: resolvingFunctions.[[Reject]] }.
+	return {
+		"[[Promise]]": promise,
+		"[[Resolve]]": resolvingFunctions["[[Resolve]]"],
+		"[[Reject]]": resolvingFunctions["[[Reject]]"]
+	};
+}