// 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,
} = (() => {
- // ☡ Because these functions are used to initialize module constants,
- // they can’t depend on imports from elsewhere.
+ const { prototype: functionPrototype } = Function;
const {
bind: functionBind,
call: functionCall,
- } = Function.prototype;
- const callBind = Reflect.apply(functionBind, functionCall, [
+ } = functionPrototype;
+ const objectConstructor = Object;
+ const proxyConstructor = Proxy;
+ const {
+ apply: reflectApply,
+ construct: reflectConstruct,
+ } = Reflect;
+ const callBind = reflectApply(functionBind, functionCall, [
functionBind,
]);
- const {
- create: objectCreate,
- defineProperty: defineOwnProperty,
- defineProperties: defineOwnProperties,
- getPrototypeOf: getPrototype,
- setPrototypeOf: setPrototype,
- } = Object;
+ const { revocable } = Proxy;
const { [ITERATOR]: arrayIterator } = Array.prototype;
const {
next: arrayIteratorNext,
};
},
};
+ const { get: wmGet, set: wmSet } = WeakMap.prototype;
+ const wsConstructor = WeakSet;
+ const { add: wsAdd, has: wsHas } = WeakSet.prototype;
+ const proxyConstructorValuesMap = new WeakMap();
+ const registerConstructedProxy = (constructor, proxy) => {
+ const values = (() => {
+ const existing = reflectApply(wmGet, proxyConstructorValuesMap, [
+ constructor,
+ ]);
+ if (existing) {
+ return existing;
+ } else {
+ const result = new wsConstructor();
+ reflectApply(wmSet, proxyConstructorValuesMap, [
+ constructor,
+ result,
+ ]);
+ return result;
+ }
+ })();
+ reflectApply(wsAdd, values, [proxy]);
+ return proxy;
+ };
const applyBaseFunction = ($, base, lengthDelta = 0) => {
- if (base === undefined) {
+ if (base === UNDEFINED) {
// No base function was provided to apply.
return $;
} else {
// A base function was provided; apply it.
const { length, name, prototype } = base;
- setPrototype($, getPrototype(base));
+ if (getPrototype($) === functionPrototype) {
+ setPrototype($, getPrototype(base));
+ } else {
+ /* do nothing */
+ }
return applyProperties($, {
length: +length + lengthDelta,
name,
}
};
const applyProperties = ($, override) => {
- if (override === undefined) {
+ if (override === UNDEFINED) {
// No properties were provided to apply.
return $;
} else {
// Properties were provided; apply them.
const { length, name, prototype } = override;
- if (!isConstructor($) || prototype === undefined) {
- // The provided function is not a constructor 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) =>
- $(...objectCreate(
- argumentIterablePrototype,
- { args: { value: $s } },
- )),
+ (...$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",
+ $s,
)[ITERATOR]();
const { value: thisValue } = iterator.next();
- return call($, thisValue, [...iterator]);
+ return reflectApply($, thisValue, [...iterator]);
},
$,
1,
),
propertyOverride,
),
- createIllegalConstructor: ($, propertyOverride = undefined) => {
- const constructor = applyProperties(
- applyBaseFunction(
- function () {
- throw new TypeError("Illegal constructor");
- },
- $,
+ createIllegalConstructor: ($, propertyOverride = UNDEFINED) =>
+ defineOwnProperty(
+ applyProperties(
+ applyBaseFunction(
+ function () {
+ throw new TypeError("Illegal constructor");
+ },
+ $,
+ ),
+ propertyOverride,
),
- propertyOverride,
- );
- return defineOwnProperty(constructor, "prototype", {
- writable: false,
- });
+ "prototype",
+ { writable: false },
+ ),
+ createProxyConstructor: (
+ handler,
+ $,
+ newTarget = UNDEFINED,
+ propertyOverride = UNDEFINED,
+ ) => {
+ const constructor = $ === UNDEFINED
+ ? function ($) {
+ return new objectConstructor($);
+ }
+ : $;
+ 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: ${handler}.`,
+ );
+ } else if (!isConstructor(constructor)) {
+ // The provided constructor is not a constructor; this is an
+ // error.
+ throw new TypeError(
+ "Piscēs: Cannot create proxy constructor from nonconstructible value.",
+ );
+ } else if (!isConstructor(target)) {
+ // The provided new target is not a constructor; this is an
+ // error.
+ throw new TypeError(
+ "Piscēs: New target must be a constructor.",
+ );
+ } else {
+ // The arguments are acceptable.
+ const C = applyProperties(
+ defineOwnProperties(
+ setPrototype(
+ function (...$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,
+ $s,
+ target,
+ );
+ const proxy = new proxyConstructor(O, handler);
+ return registerConstructedProxy(C, proxy);
+ }
+ },
+ proxyConstructor,
+ ),
+ {
+ length: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ len,
+ ),
+ name: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ `${toFunctionName(constructor.name ?? "")}Proxy`,
+ ),
+ prototype: setPropertyValues(objectCreate(null), {
+ configurable: false,
+ enumerable: false,
+ value: UNDEFINED,
+ writable: false,
+ }),
+ },
+ ),
+ propertyOverride,
+ );
+ const { name } = C;
+ return defineOwnProperties(C, {
+ revocable: setPropertyValues(objectCreate(null), {
+ configurable: true,
+ enumerable: false,
+ value: defineOwnProperties(
+ (...$s) => {
+ const O = reflectConstruct(
+ constructor,
+ $s,
+ target,
+ );
+ const proxy = revocable(O, handler);
+ return registerConstructedProxy(C, proxy);
+ },
+ {
+ length: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ len,
+ ),
+ name: defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ "revocable",
+ ),
+ },
+ ),
+ writable: true,
+ }),
+ [`is${name}`]: setPropertyValues(objectCreate(null), {
+ configurable: true,
+ enumerable: false,
+ value: defineOwnProperty(
+ ($) => {
+ const values = reflectApply(
+ wmGet,
+ proxyConstructorValuesMap,
+ [C],
+ );
+ if (values === UNDEFINED) {
+ // No values have been registered for the current
+ // constructor.
+ return false;
+ } else {
+ // One or more values has been registered for the
+ // current constructor; return whether the provided
+ // argument is one.
+ return reflectApply(wsHas, values, [$]);
+ }
+ },
+ "name",
+ defineOwnDataProperty(
+ objectCreate(null),
+ "value",
+ `is${name}`,
+ ),
+ ),
+ writable: true,
+ }),
+ });
+ }
},
};
})();
-export const {
- /**
- * Calls the provided function with the provided this value and
- * arguments list.
- *
- * ☡ This is effectively an alias for `Reflect.apply`—the arguments
- * must be passed as an arraylike.
- */
- call,
-
- /**
- * Constructs the provided function with the provided arguments list
- * and new target.
- *
- * ☡ This is effectively an alias for `Reflect.construct`—the
- * arguments must be passed as an arraylike.
- */
- construct,
-
- /** Returns whether the provided value is a constructor. */
- isConstructor,
-} = (() => {
- const { apply, construct } = Reflect;
- return {
- call: (target, thisArgument, argumentsList) =>
- apply(target, thisArgument, argumentsList),
- construct: (target, argumentsList, ...args) =>
- args.length > 0
- ? construct(target, argumentsList, args[0])
- : construct(target, argumentsList),
- isConstructor: ($) =>
- completesNormally(() =>
- // Try constructing a new object with the provided value as its
- // `new.target`. This will throw if the provided value is not a
- // constructor.
- construct(function () {}, [], $)
- ),
- };
-})();
+/**
+ * Calls the provided function with the provided this value and
+ * arguments list.
+ *
+ * ☡ This is effectively an alias for `Reflect.apply`—the arguments
+ * must be passed as an arraylike.
+ */
+export const call = createArrowFunction(Reflect.apply, {
+ name: "call",
+});
/**
* Returns whether calling the provided function with no `this` value
}
};
+/**
+ * Constructs the provided function with the provided arguments list
+ * and new target.
+ *
+ * ☡ This is effectively an alias for `Reflect.construct`—the
+ * arguments must be passed as an arraylike.
+ */
+export const construct = createArrowFunction(Reflect.construct);
+
/**
* Returns the provided value.
*
/** Returns whether the provided value is callable. */
export const isCallable = ($) => typeof $ === "function";
+/** Returns whether the provided value is a constructor. */
+export const isConstructor = ($) =>
+ completesNormally(() =>
+ // Try constructing a new object with the provided value as its
+ // `new.target`. This will throw if the provided value is not a
+ // constructor.
+ construct(function () {}, [], $)
+ );
+
+/**
+ * Calls the provided callback with the provided argument if the
+ * provided argument is not nullish; otherwise, returns the provided
+ * argument unmodified.
+ */
+export const maybe = ($, callback) => $ == null ? $ : callback($);
+
/**
* Returns whether the provided object inherits from the prototype of
* the provided function.
Lady’s Gitweb / Pisces / blobdiff