webpack/lib/util/StackedSetMap.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support 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 Tobias Koppers @sokra
*/
"use strict";

const util = require("util");

const TOMBSTONE = {};
const UNDEFINED_MARKER = {};

class StackedSetMap {
	constructor(parentStack) {
		this.stack = parentStack === undefined ? [] : parentStack.slice();
		this.map = new Map();
		this.stack.push(this.map);
	}

	add(item) {
		this.map.set(item, true);
	}

	set(item, value) {
		this.map.set(item, value === undefined ? UNDEFINED_MARKER : value);
	}

	delete(item) {
		if (this.stack.length > 1) {
			this.map.set(item, TOMBSTONE);
		} else {
			this.map.delete(item);
		}
	}

	has(item) {
		const topValue = this.map.get(item);
		if (topValue !== undefined) return topValue !== TOMBSTONE;
		if (this.stack.length > 1) {
			for (var i = this.stack.length - 2; i >= 0; i--) {
				const value = this.stack[i].get(item);
				if (value !== undefined) {
					this.map.set(item, value);
					return value !== TOMBSTONE;
				}
			}
			this.map.set(item, TOMBSTONE);
		}
		return false;
	}

	get(item) {
		const topValue = this.map.get(item);
		if (topValue !== undefined) {
			return topValue === TOMBSTONE || topValue === UNDEFINED_MARKER
				? undefined
				: topValue;
		}
		if (this.stack.length > 1) {
			for (var i = this.stack.length - 2; i >= 0; i--) {
				const value = this.stack[i].get(item);
				if (value !== undefined) {
					this.map.set(item, value);
					return value === TOMBSTONE || value === UNDEFINED_MARKER
						? undefined
						: value;
				}
			}
			this.map.set(item, TOMBSTONE);
		}
		return undefined;
	}

	_compress() {
		if (this.stack.length === 1) return;
		this.map = new Map();
		for (const data of this.stack) {
			for (const pair of data) {
				if (pair[1] === TOMBSTONE) {
					this.map.delete(pair[0]);
				} else {
					this.map.set(pair[0], pair[1]);
				}
			}
		}
		this.stack = [this.map];
	}

	asArray() {
		this._compress();
		return Array.from(this.map.entries(), pair => pair[0]);
	}

	asSet() {
		return new Set(this.asArray());
	}

	asPairArray() {
		this._compress();
		return Array.from(this.map.entries(), pair =>
			/** @type {[TODO, TODO]} */ (pair[1] === UNDEFINED_MARKER
				? [pair[0], undefined]
				: pair)
		);
	}

	asMap() {
		return new Map(this.asPairArray());
	}

	get size() {
		this._compress();
		return this.map.size;
	}

	createChild() {
		return new StackedSetMap(this.stack);
	}

	get length() {
		throw new Error("This is no longer an Array");
	}

	set length(value) {
		throw new Error("This is no longer an Array");
	}
}

// TODO remove in webpack 5
StackedSetMap.prototype.push = util.deprecate(
	/**
	 * @deprecated
	 * @this {StackedSetMap}
	 * @param {any} item Item to add
	 * @returns {void}
	 */
	function(item) {
		this.add(item);
	},
	"This is no longer an Array: Use add instead."
);

module.exports = StackedSetMap;