webpack/lib/resolve/getResolveOptionsKey.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Alexander Akait @alexander-akait
*/

"use strict";

/** @import { ResolveOptionsWithDependencyType } from "./ResolverFactory" */

/** @type {WeakMap<EXPECTED_OBJECT | EXPECTED_FUNCTION, number>} */
const identities = new WeakMap();
let nextIdentity = 0;

/**
 * Serializes resolve options into a cache key. Plain JSON values and regular expressions are keyed by content; functions, class instances and `unsafeCache` objects by identity, which holds only within this process.
 * @param {ResolveOptionsWithDependencyType} options resolve options
 * @returns {{ key: string, persistent: boolean }} the key, and whether it means the same in another process
 */
const getResolveOptionsKey = (options) => {
	let persistent = true;
	const key = JSON.stringify(
		options,
		/**
		 * @this {Record<string, unknown>}
		 * @param {string} name property name
		 * @param {unknown} value value, after any `toJSON()`
		 * @returns {unknown} value to serialize
		 */
		function replacer(name, value) {
			// `toJSON()` already ran, so a plugin could pass for plain data
			value = this[name];
			if (
				value === null ||
				(typeof value !== "object" && typeof value !== "function") ||
				Array.isArray(value)
			) {
				return value;
			}
			if (value instanceof RegExp) return { regexp: value.toString() };
			const prototype = Object.getPrototypeOf(value);
			if (
				name !== "unsafeCache" &&
				(prototype === Object.prototype || prototype === null)
			) {
				return value;
			}
			let identity = identities.get(value);
			if (identity === undefined) {
				identity = nextIdentity++;
				identities.set(value, identity);
			}
			persistent = false;
			return { identity };
		}
	);
	return { key, persistent };
};

module.exports = getResolveOptionsKey;