// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at <https://mozilla.org/MPL/2.0/>.
-import { ITERATOR, toFunctionName, toLength } from "./value.js";
+import {
+ ITERATOR,
+ toFunctionName,
+ toLength,
+ type,
+ UNDEFINED,
+} from "./value.js";
+import {
+ defineOwnDataProperty,
+ defineOwnProperties,
+ defineOwnProperty,
+ getOwnPropertyDescriptor,
+ getPrototype,
+ objectCreate,
+ setPropertyValues,
+ setPrototype,
+} from "./object.js";
export const {
/**
* be used to override `length`, `name`, and `prototype`.
*/
createIllegalConstructor,
+
+ /**
+ * Returns a constructor which produces a new constructor which wraps
+ * the provided constructor, but returns a proxy of the result using
+ * the provided handler.
+ *
+ * The resulting constructor inherits from, and has the same basic
+ * shape as, `Proxy`.
+ *
+ * If a base constructor is not provided, `Object` will be used.
+ *
+ * If a third argument is provided, it is used as the target for the
+ * provided constructor when it is constructed. This can be used to
+ * prevent leakage of the provided constructor to superclasses
+ * through `new.target`.
+ *
+ * The `length` of the provided function will be preserved in the new
+ * one. A fourth argument may be used to override `length` and
+ * `name`.
+ *
+ * ※ `.prototype` will be present, but undefined, on the resulting
+ * constructor. This differs from the behaviour of `Proxy`, for which
+ * `.prototype` is not present at all. It is not presently possible
+ * to create a constructor with no `.prototype` property in
+ * Ecmascript code.
+ */
+ createProxyConstructor,
} = (() => {
const { prototype: functionPrototype } = Function;
const {
bind: functionBind,
call: functionCall,
} = functionPrototype;
- const { apply: reflectApply } = Reflect;
+ const objectConstructor = Object;
+ const proxyConstructor = Proxy;
const {
- create: objectCreate,
- defineProperty: defineOwnProperty,
- defineProperties: defineOwnProperties,
- hasOwn: hasOwnProperty,
- getPrototypeOf: getPrototype,
- setPrototypeOf: setPrototype,
- } = Object;
+ apply: reflectApply,
+ construct: reflectConstruct,
+ } = Reflect;
const callBind = reflectApply(functionBind, functionCall, [
functionBind,
]);
+ const { revocable } = Proxy;
const { [ITERATOR]: arrayIterator } = Array.prototype;
const {
next: arrayIteratorNext,
},
};
const applyBaseFunction = ($, base, lengthDelta = 0) => {
- if (base === undefined) {
+ if (base === UNDEFINED) {
// No base function was provided to apply.
return $;
} else {
}
};
const applyProperties = ($, override) => {
- if (override === undefined) {
+ if (override === UNDEFINED) {
// No properties were provided to apply.
return $;
} else {
// Properties were provided; apply them.
const { length, name, prototype } = override;
- if (!hasOwnProperty($, "prototype") || prototype === undefined) {
- // The provided function has no `.prototype` or no prototype
- // value was provided.
+ if (
+ prototype === UNDEFINED ||
+ !getOwnPropertyDescriptor($, "prototype")?.writable
+ ) {
+ // The provided function has no `.prototype`, its prototype is
+ // not writable, or no prototype value was provided.
//
// Do not modify the prototype property of the provided
// function.
//
// Change the prototype property of the provided function to
// match.
- defineOwnProperty($, "prototype", { value: prototype });
+ defineOwnProperty(
+ $,
+ "prototype",
+ defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ prototype,
+ ),
+ );
}
return defineOwnProperties($, {
- length: {
- value: toLength(length === undefined ? $.length : length),
- },
- name: {
- value: toFunctionName(
- name === undefined ? $.name ?? "" : name,
- ),
- },
+ length: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ toLength(length === UNDEFINED ? $.length : length),
+ ),
+ name: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ toFunctionName(name === UNDEFINED ? $.name ?? "" : name),
+ ),
});
}
};
callBind(
$,
boundThis,
- ...objectCreate(
- argumentIterablePrototype,
- { args: { value: boundArgs } },
+ ...defineOwnDataProperty(
+ objectCreate(argumentIterablePrototype),
+ "args",
+ boundArgs,
),
),
- createArrowFunction: ($, propertyOverride = undefined) =>
+ createArrowFunction: ($, propertyOverride = UNDEFINED) =>
applyProperties(
applyBaseFunction(
- (...$s) => reflectApply($, undefined, $s),
+ (...$s) => reflectApply($, UNDEFINED, $s),
$,
),
propertyOverride,
),
- createCallableFunction: ($, propertyOverride = undefined) =>
+ createCallableFunction: ($, propertyOverride = UNDEFINED) =>
applyProperties(
applyBaseFunction(
(...$s) => {
- const iterator = objectCreate(
- argumentIterablePrototype,
- { args: { value: $s } },
+ const iterator = defineOwnDataProperty(
+ objectCreate(argumentIterablePrototype),
+ "args",
+ $s,
)[ITERATOR]();
const { value: thisValue } = iterator.next();
return reflectApply($, thisValue, [...iterator]);
),
propertyOverride,
),
- createIllegalConstructor: ($, propertyOverride = undefined) =>
+ createIllegalConstructor: ($, propertyOverride = UNDEFINED) =>
defineOwnProperty(
applyProperties(
applyBaseFunction(
"prototype",
{ writable: false },
),
+ createProxyConstructor: (
+ handler,
+ $,
+ newTarget = UNDEFINED,
+ propertyOverride = UNDEFINED,
+ ) => {
+ const constructor = $ === UNDEFINED ? objectConstructor : $;
+ const target = newTarget === UNDEFINED ? constructor : newTarget;
+ const len = toLength(constructor.length);
+ if (!(type(handler) === "object")) {
+ // The provided handler is not an object; this is an error.
+ throw new TypeError(
+ `Piscēs: Proxy handler must be an object, but got: ${handler}.`,
+ );
+ } else if (!isConstructor(constructor)) {
+ // The provided constructor is not a constructor; this is an
+ // error.
+ throw new TypeError(
+ "Piscēs: Cannot create proxy constructor from nonconstructible value.",
+ );
+ } else if (!isConstructor(target)) {
+ // The provided new target is not a constructor; this is an
+ // error.
+ throw new TypeError(
+ "Piscēs: New target must be a constructor.",
+ );
+ } else {
+ // The arguments are acceptable.
+ return applyProperties(
+ defineOwnProperties(
+ setPrototype(
+ function C(...$s) {
+ if (new.target === UNDEFINED) {
+ // The constructor was not called with new; this is
+ // an error.
+ throw new TypeError(
+ `Piscēs: ${
+ C.name ?? "Proxy"
+ } must be called with new.`,
+ );
+ } else {
+ // The constructor was called with new; return the
+ // appropriate proxy.
+ const O = reflectConstruct(
+ constructor,
+ $s,
+ target,
+ );
+ return new proxyConstructor(O, handler);
+ }
+ },
+ proxyConstructor,
+ ),
+ {
+ length: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ len,
+ ),
+ name: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ `${toFunctionName(constructor.name ?? "")}Proxy`,
+ ),
+ prototype: setPropertyValues(objectCreate(null), {
+ configurable: false,
+ enumerable: false,
+ value: UNDEFINED,
+ writable: false,
+ }),
+ revocable: setPropertyValues(objectCreate(null), {
+ configurable: true,
+ enumerable: false,
+ value: defineOwnProperties(
+ (...$s) => {
+ const O = reflectConstruct(
+ constructor,
+ $s,
+ target,
+ );
+ return revocable(O, handler);
+ },
+ {
+ length: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ len,
+ ),
+ name: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ "revocable",
+ ),
+ },
+ ),
+ writable: true,
+ }),
+ },
+ ),
+ propertyOverride,
+ );
+ }
+ },
};
})();
Lady’s Gitweb / Pisces / blobdiff