X-Git-Url: https://git.ladys.computer/Pisces/blobdiff_plain/70b032d26faece9d6573e6f0b2375f071bbcc866..refs/heads/current:/value.js

diff --git a/value.js b/value.js
index 83c1e18..cf858ad 100644
--- a/value.js
+++ b/value.js
@@ -173,6 +173,93 @@ export const POSITIVE_ZERO = 0;
 /** The undefined primitive. */
 export const UNDEFINED = undefined;
 
+/**
+ * Completes the provided property descriptor by setting missing values
+ * to their defaults.
+ *
+ * ※ This method modifies the provided object and returns undefined.
+ */
+export const completePropertyDescriptor = (Desc) => {
+  if (Desc === UNDEFINED) {
+    throw new TypeError(
+      "Piscēs: Cannot complete undefined property descriptor.",
+    );
+  } else if (!("get" in Desc || "set" in Desc)) {
+    // This is a generic or data descriptor.
+    if (!("value" in Desc)) {
+      // `value` is not defined on this.
+      Desc.value = UNDEFINED;
+    } else {
+      // `value` is already defined on this.
+      /* do nothing */
+    }
+    if (!("writable" in Desc)) {
+      // `writable` is not defined on this.
+      Desc.writable = false;
+    } else {
+      // `writable` is already defined on this.
+      /* do nothing */
+    }
+  } else {
+    // This is not a generic or data descriptor.
+    if (!("get" in Desc)) {
+      // `get` is not defined on this.
+      Desc.get = UNDEFINED;
+    } else {
+      // `get` is already defined on this.
+      /* do nothing */
+    }
+    if (!("set" in Desc)) {
+      // `set` is not defined on this.
+      Desc.set = UNDEFINED;
+    } else {
+      // `set` is already defined on this.
+      /* do nothing */
+    }
+  }
+  if (!("enumerable" in Desc)) {
+    // `enumerable` is not defined on this.
+    Desc.enumerable = false;
+  } else {
+    // `enumerable` is already defined on this.
+    /* do nothing */
+  }
+  if (!("configurable" in Desc)) {
+    // `configurable` is not defined on this.
+    Desc.configurable = false;
+  } else {
+    // `configurable` is already defined on this.
+    /* do nothing */
+  }
+};
+
+/** Gets whether the provided value is an accessor descrtiptor. */
+export const isAccessorDescriptor = (Desc) =>
+  Desc !== UNDEFINED && ("get" in Desc || "set" in Desc);
+
+/** Gets whether the provided value is a data descrtiptor. */
+export const isDataDescriptor = (Desc) =>
+  Desc !== UNDEFINED && ("value" in Desc || "writable" in Desc);
+
+/**
+ * Gets whether the provided value is a fully‐populated property
+ * descriptor.
+ */
+export const isFullyPopulatedDescriptor = (Desc) =>
+  Desc !== UNDEFINED &&
+  ("value" in Desc && "writable" in Desc ||
+    "get" in Desc && "set" in Desc) &&
+  "enumerable" in Desc && "configurable" in Desc;
+
+/**
+ * Gets whether the provided value is a generic (not accessor or data)
+ * descrtiptor.
+ */
+export const isGenericDescriptor = (Desc) =>
+  Desc !== UNDEFINED &&
+  !("get" in Desc || "set" in Desc || "value" in Desc ||
+    "writable" in Desc);
+
 export const {
   /**
    * Returns the primitive value of the provided object per its
@@ -186,6 +273,12 @@ export const {
    */
   ordinaryToPrimitive,
 
+  /**
+   * Returns a string function name generated from the provided value
+   * and optional prefix.
+   */
+  toFunctionName,
+
   /**
    * Returns the provided value converted to a primitive, or throws if
    * no such conversion is possible.
@@ -199,6 +292,10 @@ export const {
   toPrimitive,
 } = (() => {
   const { apply: call } = Reflect;
+  const getSymbolDescription = Object.getOwnPropertyDescriptor(
+    Symbol.prototype,
+    "description",
+  ).get;
 
   return {
     ordinaryToPrimitive: (O, hint) => {
@@ -226,6 +323,21 @@ export const {
         "Piscēs: Unable to convert object to primitive",
       );
     },
+    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 ? "" : `[${description}]`;
+        } else {
+          // The provided value not a symbol; convert it to a string
+          // property key.
+          return `${key}`;
+        }
+      })();
+      return prefix !== UNDEFINED ? `${prefix} ${name}` : name;
+    },
     toPrimitive: ($, preferredType = "default") => {
       const hint = `${preferredType}`;
       if (
@@ -238,8 +350,8 @@ export const {
         );
       } else if (type($) === "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") {
@@ -336,6 +448,15 @@ export const {
   };
 })();
 
+/**
+ * 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.