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1 files changed, 35 insertions, 0 deletions

diff --git a/node_modules/webpack/lib/util/cachedMerge.js b/node_modules/webpack/lib/util/cachedMerge.js
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+++ b/node_modules/webpack/lib/util/cachedMerge.js
@@ -0,0 +1,35 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+"use strict";
+
+const mergeCache = new WeakMap();
+
+/**
+ * Merges two given objects and caches the result to avoid computation if same objects passed as arguments again.
+ * @example
+ * // performs Object.assign(first, second), stores the result in WeakMap and returns result
+ * cachedMerge({a: 1}, {a: 2})
+ * {a: 2}
+ *  // when same arguments passed, gets the result from WeakMap and returns it.
+ * cachedMerge({a: 1}, {a: 2})
+ * {a: 2}
+ * @param {object} first first object
+ * @param {object} second second object
+ * @returns {object} merged object of first and second object
+ */
+const cachedMerge = (first, second) => {
+	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 = Object.assign({}, first, second);
+	innerCache.set(second, newMerge);
+	return newMerge;
+};
+
+module.exports = cachedMerge;