webpack/lib/util/cleverMerge.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";

/** @type {WeakMap<object, WeakMap<object, object>>} */
const mergeCache = new WeakMap();
/** @type {WeakMap<object, Map<string, Map<string|number|boolean, object>>>} */
const setPropertyCache = new WeakMap();
const DELETE = Symbol("DELETE");
const DYNAMIC_INFO = Symbol("cleverMerge dynamic info");

/**
 * Merges two given objects and caches the result to avoid computation if same objects passed as arguments again.
 * @template T
 * @template O
 * @example
 * // performs cleverMerge(first, second), stores the result in WeakMap and returns result
 * cachedCleverMerge({a: 1}, {a: 2})
 * {a: 2}
 *  // when same arguments passed, gets the result from WeakMap and returns it.
 * cachedCleverMerge({a: 1}, {a: 2})
 * {a: 2}
 * @param {T} first first object
 * @param {O} second second object
 * @returns {T & O | T | O} merged object of first and second object
 */
const cachedCleverMerge = (first, second) => {
	if (second === undefined) return first;
	if (first === undefined) return second;
	if (typeof second !== "object" || second === null) return second;
	if (typeof first !== "object" || first === null) return first;

	let innerCache = mergeCache.get(first);
	if (innerCache === undefined) {
		innerCache = new WeakMap();
		mergeCache.set(first, innerCache);
	}
	const prevMerge = innerCache.get(second);
	if (prevMerge !== undefined) return prevMerge;
	const newMerge = _cleverMerge(first, second, true);
	innerCache.set(second, newMerge);
	return newMerge;
};

/**
 * @template T
 * @param {Partial<T>} obj object
 * @param {string} property property
 * @param {string|number|boolean} value assignment value
 * @returns {T} new object
 */
const cachedSetProperty = (obj, property, value) => {
	let mapByProperty = setPropertyCache.get(obj);

	if (mapByProperty === undefined) {
		mapByProperty = new Map();
		setPropertyCache.set(obj, mapByProperty);
	}

	let mapByValue = mapByProperty.get(property);

	if (mapByValue === undefined) {
		mapByValue = new Map();
		mapByProperty.set(property, mapByValue);
	}

	let result = mapByValue.get(value);

	if (result) return result;

	result = {
		...obj,
		[property]: value
	};
	mapByValue.set(value, result);

	return result;
};

/**
 * @typedef {Object} ObjectParsedPropertyEntry
 * @property {any | undefined} base base value
 * @property {string | undefined} byProperty the name of the selector property
 * @property {Map<string, any>} byValues value depending on selector property, merged with base
 */

/**
 * @typedef {Object} ParsedObject
 * @property {Map<string, ObjectParsedPropertyEntry>} static static properties (key is property name)
 * @property {{ byProperty: string, fn: Function } | undefined} dynamic dynamic part
 */

/** @type {WeakMap<object, ParsedObject>} */
const parseCache = new WeakMap();

/**
 * @param {object} obj the object
 * @returns {ParsedObject} parsed object
 */
const cachedParseObject = obj => {
	const entry = parseCache.get(obj);
	if (entry !== undefined) return entry;
	const result = parseObject(obj);
	parseCache.set(obj, result);
	return result;
};

/**
 * @param {object} obj the object
 * @returns {ParsedObject} parsed object
 */
const parseObject = obj => {
	const info = new Map();
	let dynamicInfo;
	const getInfo = p => {
		const entry = info.get(p);
		if (entry !== undefined) return entry;
		const newEntry = {
			base: undefined,
			byProperty: undefined,
			byValues: undefined
		};
		info.set(p, newEntry);
		return newEntry;
	};
	for (const key of Object.keys(obj)) {
		if (key.startsWith("by")) {
			const byProperty = key;
			const byObj = obj[byProperty];
			if (typeof byObj === "object") {
				for (const byValue of Object.keys(byObj)) {
					const obj = byObj[byValue];
					for (const key of Object.keys(obj)) {
						const entry = getInfo(key);
						if (entry.byProperty === undefined) {
							entry.byProperty = byProperty;
							entry.byValues = new Map();
						} else if (entry.byProperty !== byProperty) {
							throw new Error(
								`${byProperty} and ${entry.byProperty} for a single property is not supported`
							);
						}
						entry.byValues.set(byValue, obj[key]);
						if (byValue === "default") {
							for (const otherByValue of Object.keys(byObj)) {
								if (!entry.byValues.has(otherByValue))
									entry.byValues.set(otherByValue, undefined);
							}
						}
					}
				}
			} else if (typeof byObj === "function") {
				if (dynamicInfo === undefined) {
					dynamicInfo = {
						byProperty: key,
						fn: byObj
					};
				} else {
					throw new Error(
						`${key} and ${dynamicInfo.byProperty} when both are functions is not supported`
					);
				}
			} else {
				const entry = getInfo(key);
				entry.base = obj[key];
			}
		} else {
			const entry = getInfo(key);
			entry.base = obj[key];
		}
	}
	return {
		static: info,
		dynamic: dynamicInfo
	};
};

/**
 * @param {Map<string, ObjectParsedPropertyEntry>} info static properties (key is property name)
 * @param {{ byProperty: string, fn: Function } | undefined} dynamicInfo dynamic part
 * @returns {object} the object
 */
const serializeObject = (info, dynamicInfo) => {
	const obj = {};
	// Setup byProperty structure
	for (const entry of info.values()) {
		if (entry.byProperty !== undefined) {
			const byObj = (obj[entry.byProperty] = obj[entry.byProperty] || {});
			for (const byValue of entry.byValues.keys()) {
				byObj[byValue] = byObj[byValue] || {};
			}
		}
	}
	for (const [key, entry] of info) {
		if (entry.base !== undefined) {
			obj[key] = entry.base;
		}
		// Fill byProperty structure
		if (entry.byProperty !== undefined) {
			const byObj = (obj[entry.byProperty] = obj[entry.byProperty] || {});
			for (const byValue of Object.keys(byObj)) {
				const value = getFromByValues(entry.byValues, byValue);
				if (value !== undefined) byObj[byValue][key] = value;
			}
		}
	}
	if (dynamicInfo !== undefined) {
		obj[dynamicInfo.byProperty] = dynamicInfo.fn;
	}
	return obj;
};

const VALUE_TYPE_UNDEFINED = 0;
const VALUE_TYPE_ATOM = 1;
const VALUE_TYPE_ARRAY_EXTEND = 2;
const VALUE_TYPE_OBJECT = 3;
const VALUE_TYPE_DELETE = 4;

/**
 * @param {any} value a single value
 * @returns {VALUE_TYPE_UNDEFINED | VALUE_TYPE_ATOM | VALUE_TYPE_ARRAY_EXTEND | VALUE_TYPE_OBJECT | VALUE_TYPE_DELETE} value type
 */
const getValueType = value => {
	if (value === undefined) {
		return VALUE_TYPE_UNDEFINED;
	} else if (value === DELETE) {
		return VALUE_TYPE_DELETE;
	} else if (Array.isArray(value)) {
		if (value.lastIndexOf("...") !== -1) return VALUE_TYPE_ARRAY_EXTEND;
		return VALUE_TYPE_ATOM;
	} else if (
		typeof value === "object" &&
		value !== null &&
		(!value.constructor || value.constructor === Object)
	) {
		return VALUE_TYPE_OBJECT;
	}
	return VALUE_TYPE_ATOM;
};

/**
 * Merges two objects. Objects are deeply clever merged.
 * Arrays might reference the old value with "...".
 * Non-object values take preference over object values.
 * @template T
 * @template O
 * @param {T} first first object
 * @param {O} second second object
 * @returns {T & O | T | O} merged object of first and second object
 */
const cleverMerge = (first, second) => {
	if (second === undefined) return first;
	if (first === undefined) return second;
	if (typeof second !== "object" || second === null) return second;
	if (typeof first !== "object" || first === null) return first;

	return _cleverMerge(first, second, false);
};

/**
 * Merges two objects. Objects are deeply clever merged.
 * @param {object} first first object
 * @param {object} second second object
 * @param {boolean} internalCaching should parsing of objects and nested merges be cached
 * @returns {object} merged object of first and second object
 */
const _cleverMerge = (first, second, internalCaching = false) => {
	const firstObject = internalCaching
		? cachedParseObject(first)
		: parseObject(first);
	const { static: firstInfo, dynamic: firstDynamicInfo } = firstObject;

	// If the first argument has a dynamic part we modify the dynamic part to merge the second argument
	if (firstDynamicInfo !== undefined) {
		let { byProperty, fn } = firstDynamicInfo;
		const fnInfo = fn[DYNAMIC_INFO];
		if (fnInfo) {
			second = internalCaching
				? cachedCleverMerge(fnInfo[1], second)
				: cleverMerge(fnInfo[1], second);
			fn = fnInfo[0];
		}
		const newFn = (...args) => {
			const fnResult = fn(...args);
			return internalCaching
				? cachedCleverMerge(fnResult, second)
				: cleverMerge(fnResult, second);
		};
		newFn[DYNAMIC_INFO] = [fn, second];
		return serializeObject(firstObject.static, { byProperty, fn: newFn });
	}

	// If the first part is static only, we merge the static parts and keep the dynamic part of the second argument
	const secondObject = internalCaching
		? cachedParseObject(second)
		: parseObject(second);
	const { static: secondInfo, dynamic: secondDynamicInfo } = secondObject;
	/** @type {Map<string, ObjectParsedPropertyEntry>} */
	const resultInfo = new Map();
	for (const [key, firstEntry] of firstInfo) {
		const secondEntry = secondInfo.get(key);
		const entry =
			secondEntry !== undefined
				? mergeEntries(firstEntry, secondEntry, internalCaching)
				: firstEntry;
		resultInfo.set(key, entry);
	}
	for (const [key, secondEntry] of secondInfo) {
		if (!firstInfo.has(key)) {
			resultInfo.set(key, secondEntry);
		}
	}
	return serializeObject(resultInfo, secondDynamicInfo);
};

/**
 * @param {ObjectParsedPropertyEntry} firstEntry a
 * @param {ObjectParsedPropertyEntry} secondEntry b
 * @param {boolean} internalCaching should parsing of objects and nested merges be cached
 * @returns {ObjectParsedPropertyEntry} new entry
 */
const mergeEntries = (firstEntry, secondEntry, internalCaching) => {
	switch (getValueType(secondEntry.base)) {
		case VALUE_TYPE_ATOM:
		case VALUE_TYPE_DELETE:
			// No need to consider firstEntry at all
			// second value override everything
			// = second.base + second.byProperty
			return secondEntry;
		case VALUE_TYPE_UNDEFINED:
			if (!firstEntry.byProperty) {
				// = first.base + second.byProperty
				return {
					base: firstEntry.base,
					byProperty: secondEntry.byProperty,
					byValues: secondEntry.byValues
				};
			} else if (firstEntry.byProperty !== secondEntry.byProperty) {
				throw new Error(
					`${firstEntry.byProperty} and ${secondEntry.byProperty} for a single property is not supported`
				);
			} else {
				// = first.base + (first.byProperty + second.byProperty)
				// need to merge first and second byValues
				const newByValues = new Map(firstEntry.byValues);
				for (const [key, value] of secondEntry.byValues) {
					const firstValue = getFromByValues(firstEntry.byValues, key);
					newByValues.set(
						key,
						mergeSingleValue(firstValue, value, internalCaching)
					);
				}
				return {
					base: firstEntry.base,
					byProperty: firstEntry.byProperty,
					byValues: newByValues
				};
			}
		default: {
			if (!firstEntry.byProperty) {
				// The simple case
				// = (first.base + second.base) + second.byProperty
				return {
					base: mergeSingleValue(
						firstEntry.base,
						secondEntry.base,
						internalCaching
					),
					byProperty: secondEntry.byProperty,
					byValues: secondEntry.byValues
				};
			}
			let newBase;
			const intermediateByValues = new Map(firstEntry.byValues);
			for (const [key, value] of intermediateByValues) {
				intermediateByValues.set(
					key,
					mergeSingleValue(value, secondEntry.base, internalCaching)
				);
			}
			if (
				Array.from(firstEntry.byValues.values()).every(value => {
					const type = getValueType(value);
					return type === VALUE_TYPE_ATOM || type === VALUE_TYPE_DELETE;
				})
			) {
				// = (first.base + second.base) + ((first.byProperty + second.base) + second.byProperty)
				newBase = mergeSingleValue(
					firstEntry.base,
					secondEntry.base,
					internalCaching
				);
			} else {
				// = first.base + ((first.byProperty (+default) + second.base) + second.byProperty)
				newBase = firstEntry.base;
				if (!intermediateByValues.has("default"))
					intermediateByValues.set("default", secondEntry.base);
			}
			if (!secondEntry.byProperty) {
				// = first.base + (first.byProperty + second.base)
				return {
					base: newBase,
					byProperty: firstEntry.byProperty,
					byValues: intermediateByValues
				};
			} else if (firstEntry.byProperty !== secondEntry.byProperty) {
				throw new Error(
					`${firstEntry.byProperty} and ${secondEntry.byProperty} for a single property is not supported`
				);
			}
			const newByValues = new Map(intermediateByValues);
			for (const [key, value] of secondEntry.byValues) {
				const firstValue = getFromByValues(intermediateByValues, key);
				newByValues.set(
					key,
					mergeSingleValue(firstValue, value, internalCaching)
				);
			}
			return {
				base: newBase,
				byProperty: firstEntry.byProperty,
				byValues: newByValues
			};
		}
	}
};

/**
 * @param {Map<string, any>} byValues all values
 * @param {string} key value of the selector
 * @returns {any | undefined} value
 */
const getFromByValues = (byValues, key) => {
	if (key !== "default" && byValues.has(key)) {
		return byValues.get(key);
	}
	return byValues.get("default");
};

/**
 * @param {any} a value
 * @param {any} b value
 * @param {boolean} internalCaching should parsing of objects and nested merges be cached
 * @returns {any} value
 */
const mergeSingleValue = (a, b, internalCaching) => {
	const bType = getValueType(b);
	const aType = getValueType(a);
	switch (bType) {
		case VALUE_TYPE_DELETE:
		case VALUE_TYPE_ATOM:
			return b;
		case VALUE_TYPE_OBJECT: {
			return aType !== VALUE_TYPE_OBJECT
				? b
				: internalCaching
				? cachedCleverMerge(a, b)
				: cleverMerge(a, b);
		}
		case VALUE_TYPE_UNDEFINED:
			return a;
		case VALUE_TYPE_ARRAY_EXTEND:
			switch (
				aType !== VALUE_TYPE_ATOM
					? aType
					: Array.isArray(a)
					? VALUE_TYPE_ARRAY_EXTEND
					: VALUE_TYPE_OBJECT
			) {
				case VALUE_TYPE_UNDEFINED:
					return b;
				case VALUE_TYPE_DELETE:
					return b.filter(item => item !== "...");
				case VALUE_TYPE_ARRAY_EXTEND: {
					const newArray = [];
					for (const item of b) {
						if (item === "...") {
							for (const item of a) {
								newArray.push(item);
							}
						} else {
							newArray.push(item);
						}
					}
					return newArray;
				}
				case VALUE_TYPE_OBJECT:
					return b.map(item => (item === "..." ? a : item));
				default:
					throw new Error("Not implemented");
			}
		default:
			throw new Error("Not implemented");
	}
};

/**
 * @template T
 * @param {T} obj the object
 * @returns {T} the object without operations like "..." or DELETE
 */
const removeOperations = obj => {
	const newObj = /** @type {T} */ ({});
	for (const key of Object.keys(obj)) {
		const value = obj[key];
		const type = getValueType(value);
		switch (type) {
			case VALUE_TYPE_UNDEFINED:
			case VALUE_TYPE_DELETE:
				break;
			case VALUE_TYPE_OBJECT:
				newObj[key] = removeOperations(value);
				break;
			case VALUE_TYPE_ARRAY_EXTEND:
				newObj[key] = value.filter(i => i !== "...");
				break;
			default:
				newObj[key] = value;
				break;
		}
	}
	return newObj;
};

/**
 * @template T
 * @template {string} P
 * @param {T} obj the object
 * @param {P} byProperty the by description
 * @param  {...any} values values
 * @returns {Omit<T, P>} object with merged byProperty
 */
const resolveByProperty = (obj, byProperty, ...values) => {
	if (typeof obj !== "object" || obj === null || !(byProperty in obj)) {
		return obj;
	}
	const { [byProperty]: _byValue, ..._remaining } = /** @type {object} */ (obj);
	const remaining = /** @type {T} */ (_remaining);
	const byValue = /** @type {Record<string, T> | function(...any[]): T} */ (
		_byValue
	);
	if (typeof byValue === "object") {
		const key = values[0];
		if (key in byValue) {
			return cachedCleverMerge(remaining, byValue[key]);
		} else if ("default" in byValue) {
			return cachedCleverMerge(remaining, byValue.default);
		} else {
			return /** @type {T} */ (remaining);
		}
	} else if (typeof byValue === "function") {
		const result = byValue.apply(null, values);
		return cachedCleverMerge(
			remaining,
			resolveByProperty(result, byProperty, ...values)
		);
	}
};

exports.cachedSetProperty = cachedSetProperty;
exports.cachedCleverMerge = cachedCleverMerge;
exports.cleverMerge = cleverMerge;
exports.resolveByProperty = resolveByProperty;
exports.removeOperations = removeOperations;
exports.DELETE = DELETE;