!("get" in Desc || "set" in Desc || "value" in Desc ||
"writable" in Desc);
-export const {
- /**
- * Returns whether the provided value is a property descriptor record
- * as created by `toPropertyDescriptor`.
- *
- * ※ This function is provided to enable inspection of whether an
- * object uses the property descriptor record proxy implementation,
- * not as a general test of whether an object satisfies the
- * requirements for property descriptors. In most cases, a more
- * specific test, like `isAccessorDescriptor`, `isDataDescriptor`, or
- * `isGenericDescriptor`, is preferrable.
- */
- isPropertyDescriptorRecord,
-
- /**
- * Converts the provided value to a property descriptor record.
- *
- * ※ The prototype of a property descriptor record is always `null`.
- *
- * ※ Actually constructing a property descriptor object using this
- * class is only necessary if you need strict guarantees about the
- * types of its properties; the resulting object is proxied to ensure
- * the types match what one would expect from composing
- * FromPropertyDescriptor and ToPropertyDescriptor in the Ecmascript
- * specification.
- */
- toPropertyDescriptor,
-} = (() => {
- const {
- assign: setPropertyValues,
- create: objectCreate,
- defineProperty: defineOwnProperty,
- } = Object;
- const {
- apply: call,
- defineProperty: reflectDefineProperty,
- setPrototypeOf: reflectSetPrototypeOf,
- } = Reflect;
- const proxyConstructor = Proxy;
- const { add: weakSetAdd, has: weakSetHas } = WeakSet.prototype;
- const propertyDescriptorRecords = new WeakSet();
- const coercePropertyDescriptorValue = (P, V) => {
- switch (P) {
- case "configurable":
- case "enumerable":
- case "writable":
- return !!V;
- case "value":
- return V;
- case "get":
- if (V !== undefined && typeof V !== "function") {
- throw new TypeError(
- "Piscēs: Getters must be callable.",
- );
- } else {
- return V;
- }
- case "set":
- if (V !== undefined && typeof V !== "function") {
- throw new TypeError(
- "Piscēs: Setters must be callable.",
- );
- } else {
- return V;
- }
- default:
- return V;
- }
- };
- const propertyDescriptorProxyHandler = Object.freeze(
- Object.assign(
- Object.create(null),
- {
- defineProperty(O, P, Desc) {
- if (
- P === "configurable" || P === "enumerable" ||
- P === "writable" || P === "value" ||
- P === "get" || P === "set"
- ) {
- // P is a property descriptor attribute.
- const desc = setPropertyValues(objectCreate(null), Desc);
- if ("get" in desc || "set" in desc) {
- // Desc is an accessor property descriptor.
- throw new TypeError(
- "Piscēs: Property descriptor attributes must be data properties.",
- );
- } else if ("value" in desc || !(P in O)) {
- // Desc has a value or P does not already exist on O.
- desc.value = coercePropertyDescriptorValue(
- P,
- desc.value,
- );
- } else {
- // Desc is not an accessor property descriptor and has no
- // value, but an existing value is present on O.
- /* do nothing */
- }
- const isAccessorDescriptor = "get" === P || "set" === P ||
- "get" in O || "set" in O;
- const isDataDescriptor = "value" === P ||
- "writable" === P ||
- "value" in O || "writable" in O;
- if (isAccessorDescriptor && isDataDescriptor) {
- // Both accessor and data attributes will be present on O
- // after defining P.
- throw new TypeError(
- "Piscēs: Property descriptors cannot specify both accessor and data attributes.",
- );
- } else {
- // P can be safely defined on O.
- return reflectDefineProperty(O, P, desc);
- }
- } else {
- // P is not a property descriptor attribute.
- return reflectDefineProperty(O, P, Desc);
- }
- },
- setPrototypeOf(O, V) {
- if (V !== null) {
- // V is not the property descriptor prototype.
- return false;
- } else {
- // V is the property descriptor prototype.
- return reflectSetPrototypeOf(O, V);
- }
- },
- },
- ),
- );
-
- return {
- isPropertyDescriptorRecord: ($) =>
- call(weakSetHas, propertyDescriptorRecords, [$]),
- toPropertyDescriptor: (Obj) => {
- if (type(Obj) !== "object") {
- // The provided value is not an object.
- throw new TypeError(
- `Piscēs: Cannot convert primitive to property descriptor: ${O}.`,
- );
- } else {
- // The provided value is an object.
- const desc = objectCreate(null);
- if ("enumerable" in Obj) {
- // An enumerable property is specified.
- defineOwnProperty(desc, "enumerable", {
- configurable: true,
- enumerable: true,
- value: !!Obj.enumerable,
- writable: true,
- });
- } else {
- // An enumerable property is not specified.
- /* do nothing */
- }
- if ("configurable" in Obj) {
- // A configurable property is specified.
- defineOwnProperty(desc, "configurable", {
- configurable: true,
- enumerable: true,
- value: !!Obj.configurable,
- writable: true,
- });
- } else {
- // A configurable property is not specified.
- /* do nothing */
- }
- if ("value" in Obj) {
- // A value property is specified.
- defineOwnProperty(desc, "value", {
- configurable: true,
- enumerable: true,
- value: Obj.value,
- writable: true,
- });
- } else {
- // A value property is not specified.
- /* do nothing */
- }
- if ("writable" in Obj) {
- // A writable property is specified.
- defineOwnProperty(desc, "writable", {
- configurable: true,
- enumerable: true,
- value: !!Obj.writable,
- writable: true,
- });
- } else {
- // A writable property is not specified.
- /* do nothing */
- }
- if ("get" in Obj) {
- // A get property is specified.
- const getter = Obj.get;
- if (getter !== UNDEFINED && typeof getter !== "function") {
- // The getter is not callable.
- throw new TypeError("Piscēs: Getters must be callable.");
- } else {
- // The getter is callable.
- defineOwnProperty(desc, "get", {
- configurable: true,
- enumerable: true,
- value: getter,
- writable: true,
- });
- }
- } else {
- // A get property is not specified.
- /* do nothing */
- }
- if ("set" in Obj) {
- // A set property is specified.
- const setter = Obj.set;
- if (setter !== UNDEFINED && typeof setter !== "function") {
- // The setter is not callable.
- throw new TypeError("Piscēs: Setters must be callable.");
- } else {
- // The setter is callable.
- defineOwnProperty(desc, "set", {
- configurable: true,
- enumerable: true,
- value: setter,
- writable: true,
- });
- }
- } else {
- // A set property is not specified.
- /* do nothing */
- }
- if (
- ("get" in desc || "set" in desc) &&
- ("value" in desc || "writable" in desc)
- ) {
- // Both accessor and data attributes have been defined.
- throw new TypeError(
- "Piscēs: Property descriptors cannot specify both accessor and data attributes.",
- );
- } else {
- // The property descriptor is valid.
- const record = new proxyConstructor(
- desc,
- propertyDescriptorProxyHandler,
- );
- call(weakSetAdd, propertyDescriptorRecords, [record]);
- return record;
- }
- }
- },
- };
-})();
-
export const {
/**
* Returns the primitive value of the provided object per its
"Piscēs: Unable to convert object to primitive",
);
},
- toFunctionName: ($, prefix = undefined) => {
+ toFunctionName: ($, prefix = UNDEFINED) => {
const key = toPrimitive($, "string");
const name = (() => {
if (typeof key === "symbol") {
// The provided value is a symbol; format its description.
const description = call(getSymbolDescription, key, []);
- return description === undefined ? "" : `[${description}]`;
+ return description === UNDEFINED ? "" : `[${description}]`;
} else {
// The provided value not a symbol; convert it to a string
// property key.
return `${key}`;
}
})();
- return prefix !== undefined ? `${prefix} ${name}` : name;
+ return prefix !== UNDEFINED ? `${prefix} ${name}` : name;
},
toPrimitive: ($, preferredType = "default") => {
const hint = `${preferredType}`;
);
} else if (type($) === "object") {
// The provided value is an object.
- const exoticToPrim = $[TO_PRIMITIVE] ?? undefined;
- if (exoticToPrim !== undefined) {
+ const exoticToPrim = $[TO_PRIMITIVE] ?? UNDEFINED;
+ if (exoticToPrim !== UNDEFINED) {
// The provided value has an exotic primitive conversion
// method.
if (typeof exoticToPrim !== "function") {
};
})();
+/**
+ * Returns the property key (symbol or string) corresponding to the
+ * provided value.
+ */
+export const toPropertyKey = ($) => {
+ const key = toPrimitive($, "string");
+ return typeof key === "symbol" ? key : `${key}`;
+};
+
/**
* Returns a lowercase string identifying the type of the provided
* value.
Lady’s Gitweb / Pisces / blobdiff