+/**
+ * A property descriptor object.
+ *
+ * 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.
+ *
+ * Otherwise, the instance properties and methods are generic.
+ */
+export const PropertyDescriptor = (() => {
+ class PropertyDescriptor extends null {
+ /**
+ * Constructs a new property descriptor object from the provided
+ * object.
+ *
+ * The resulting object is proxied to enforce types (for example,
+ * its `enumerable` property, if defined, will always be a
+ * boolean).
+ */
+ //deno-lint-ignore constructor-super
+ constructor(Obj) {
+ if (!isObject(Obj)) {
+ // The provided value is not an object.
+ throw new TypeError(
+ "Piscēs: Cannot convert primitive to property descriptor.",
+ );
+ } else {
+ // The provided value is an object.
+ const desc = Object.create(propertyDescriptorPrototype);
+ if ("enumerable" in Obj) {
+ // An enumerable property is specified.
+ desc.enumerable = !!Obj.enumerable;
+ } else {
+ // An enumerable property is not specified.
+ /* do nothing */
+ }
+ if ("configurable" in Obj) {
+ // A configurable property is specified.
+ desc.configurable = !!Obj.configurable;
+ } else {
+ // A configurable property is not specified.
+ /* do nothing */
+ }
+ if ("value" in Obj) {
+ // A value property is specified.
+ desc.value = Obj.value;
+ } else {
+ // A value property is not specified.
+ /* do nothing */
+ }
+ if ("writable" in Obj) {
+ // A writable property is specified.
+ desc.writable = !!Obj.writable;
+ } else {
+ // A writable property is not specified.
+ /* do nothing */
+ }
+ if ("get" in Obj) {
+ // A get property is specified.
+ const getter = Obj.get;
+ if (typeof getter != "function") {
+ // The getter is not callable.
+ throw new TypeError("Piscēs: Getters must be callable.");
+ } else {
+ // The getter is callable.
+ desc.get = getter;
+ }
+ } else {
+ // A get property is not specified.
+ /* do nothing */
+ }
+ if ("set" in Obj) {
+ // A set property is specified.
+ const setter = Obj.set;
+ if (typeof setter != "function") {
+ // The setter is not callable.
+ throw new TypeError("Piscēs: Setters must be callable.");
+ } else {
+ // The setter is callable.
+ desc.set = setter;
+ }
+ } 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.
+ return new Proxy(desc, propertyDescriptorProxyHandler);
+ }
+ }
+ }
+
+ /**
+ * Completes this property descriptor by setting missing values to
+ * their defaults.
+ *
+ * This method modifies this object and returns undefined.
+ */
+ complete() {
+ if (this !== undefined && !("get" in this || "set" in this)) {
+ // This is a generic or data descriptor.
+ if (!("value" in this)) {
+ // `value` is not defined on this.
+ this.value = undefined;
+ } else {
+ // `value` is already defined on this.
+ /* do nothing */
+ }
+ if (!("writable" in this)) {
+ // `writable` is not defined on this.
+ this.writable = false;
+ } else {
+ // `writable` is already defined on this.
+ /* do nothing */
+ }
+ } else {
+ // This is not a generic or data descriptor.
+ if (!("get" in this)) {
+ // `get` is not defined on this.
+ this.get = undefined;
+ } else {
+ // `get` is already defined on this.
+ /* do nothing */
+ }
+ if (!("set" in this)) {
+ // `set` is not defined on this.
+ this.set = undefined;
+ } else {
+ // `set` is already defined on this.
+ /* do nothing */
+ }
+ }
+ if (!("enumerable" in this)) {
+ // `enumerable` is not defined on this.
+ this.enumerable = false;
+ } else {
+ // `enumerable` is already defined on this.
+ /* do nothing */
+ }
+ if (!("configurable" in this)) {
+ // `configurable` is not defined on this.
+ this.configurable = false;
+ } else {
+ // `configurable` is already defined on this.
+ /* do nothing */
+ }
+ }
+
+ /** Returns whether this is an accessor descrtiptor. */
+ get isAccessorDescriptor() {
+ return this !== undefined && ("get" in this || "set" in this);
+ }
+
+ /** Returns whether this is a data descrtiptor. */
+ get isDataDescriptor() {
+ return this !== undefined &&
+ ("value" in this || "writable" in this);
+ }
+
+ /**
+ * Returns whether this is a fully‐populated property descriptor.
+ */
+ get isFullyPopulated() {
+ return this !== undefined &&
+ ("value" in this && "writable" in this ||
+ "get" in this && "set" in this) &&
+ "enumerable" in this && "configurable" in this;
+ }
+
+ /**
+ * Returns whether this is a generic (not accessor or data)
+ * descrtiptor.
+ */
+ get isGenericDescriptor() {
+ return this !== undefined &&
+ !("get" in this || "set" in this || "value" in this ||
+ "writable" in this);
+ }
+ }
+
+ const coercePropretyDescriptorValue = (P, V) => {
+ switch (P) {
+ case "configurable":
+ case "enumerable":
+ case "writable":
+ return !!V;
+ case "value":
+ return V;
+ case "get":
+ if (typeof V != "function") {
+ throw new TypeError(
+ "Piscēs: Getters must be callable.",
+ );
+ } else {
+ return V;
+ }
+ case "set":
+ if (typeof V != "function") {
+ throw new TypeError(
+ "Piscēs: Setters must be callable.",
+ );
+ } else {
+ return V;
+ }
+ default:
+ return V;
+ }
+ };
+
+ const propertyDescriptorPrototype = PropertyDescriptor.prototype;
+
+ const propertyDescriptorProxyHandler = 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 = new PropertyDescriptor(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) {
+ // Desc has a value.
+ desc.value = coercePropretyDescriptorValue(P, desc.value);
+ } else {
+ // Desc is not an accessor property descriptor and has no
+ // value.
+ /* 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 Reflect.defineProperty(O, P, desc);
+ }
+ } else {
+ // P is not a property descriptor attribute.
+ return Reflect.defineProperty(O, P, Desc);
+ }
+ },
+ set(O, P, V, Receiver) {
+ const newValue = coercePropertyDescriptorValue(P, V);
+ 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 Reflect.set(O, prop, newValue, Receiver);
+ }
+ },
+ setPrototypeOf(O, V) {
+ if (V !== propertyDescriptorPrototype) {
+ // V is not the property descriptor prototype.
+ return false;
+ } else {
+ // V is the property descriptor prototype.
+ return Reflect.setPrototypeOf(O, V);
+ }
+ },
+ },
+ );
+
+ return PropertyDescriptor;
+})();
+
+/**
+ * Returns a new frozen shallow copy of the enumerable own properties
+ * of the provided object, according to the following rules :—
+ *
+ * - For data properties, create a nonconfigurable, nonwritable
+ * property with the same value.
+ *
+ * - For accessor properties, create a nonconfigurable accessor
+ * property with the same getter *and* setter.
+ *
+ * The prototype for the resulting object will be taken from the
+ * `prototype` property of the provided constructor, or the `prototype`
+ * of the `constructor` of the provided object if the provided
+ * constructor is undefined. If the used constructor has a nonnullish
+ * `Symbol.species`, that will be used instead.
+ */
+export const frozenCopy = (O, constructor = O?.constructor) => {
+ if (O == null) {
+ // O is null or undefined.
+ throw new TypeError(
+ "Piscēs: Cannot copy properties of null or undefined.",
+ );
+ } else {
+ // O is not null or undefined.
+ //
+ // (If not provided, the constructor will be the value of getting
+ // the `constructor` property of O.)
+ const species = constructor?.[Symbol.species] ?? constructor;
+ return Object.preventExtensions(
+ Object.create(
+ species == null || !("prototype" in species)
+ ? null
+ : species.prototype,
+ Object.fromEntries(
+ function* () {
+ for (const P of Reflect.ownKeys(O)) {
+ const Desc = Object.getOwnPropertyDescriptor(O, P);
+ if (Desc.enumerable) {
+ // P is an enumerable property.
+ yield [
+ P,
+ "get" in Desc || "set" in Desc
+ ? {
+ configurable: false,
+ enumerable: true,
+ get: Desc.get,
+ set: Desc.set,
+ }
+ : {
+ configurable: false,
+ enumerable: true,
+ value: Desc.value,
+ writable: false,
+ },
+ ];
+ } else {
+ // P is not an enumerable property.
+ /* do nothing */
+ }
+ }
+ }(),
+ ),
+ ),
+ );
+ }
+};
+
Lady’s Gitweb / Pisces / commitdiff