--- /dev/null
+var assignMergeValue = require('./_assignMergeValue'),
+ baseClone = require('./_baseClone'),
+ copyArray = require('./_copyArray'),
+ isArguments = require('./isArguments'),
+ isArray = require('./isArray'),
+ isArrayLikeObject = require('./isArrayLikeObject'),
+ isFunction = require('./isFunction'),
+ isObject = require('./isObject'),
+ isPlainObject = require('./isPlainObject'),
+ isTypedArray = require('./isTypedArray'),
+ toPlainObject = require('./toPlainObject');
+
+/**
+ * A specialized version of `baseMerge` for arrays and objects which performs
+ * deep merges and tracks traversed objects enabling objects with circular
+ * references to be merged.
+ *
+ * @private
+ * @param {Object} object The destination object.
+ * @param {Object} source The source object.
+ * @param {string} key The key of the value to merge.
+ * @param {number} srcIndex The index of `source`.
+ * @param {Function} mergeFunc The function to merge values.
+ * @param {Function} [customizer] The function to customize assigned values.
+ * @param {Object} [stack] Tracks traversed source values and their merged counterparts.
+ */
+function baseMergeDeep(object, source, key, srcIndex, mergeFunc, customizer, stack) {
+ var objValue = object[key],
+ srcValue = source[key],
+ stacked = stack.get(srcValue);
+
+ if (stacked) {
+ assignMergeValue(object, key, stacked);
+ return;
+ }
+ var newValue = customizer ? customizer(objValue, srcValue, (key + ''), object, source, stack) : undefined,
+ isCommon = newValue === undefined;
+
+ if (isCommon) {
+ newValue = srcValue;
+ if (isArray(srcValue) || isTypedArray(srcValue)) {
+ if (isArray(objValue)) {
+ newValue = srcIndex ? copyArray(objValue) : objValue;
+ }
+ else if (isArrayLikeObject(objValue)) {
+ newValue = copyArray(objValue);
+ }
+ else {
+ isCommon = false;
+ newValue = baseClone(srcValue);
+ }
+ }
+ else if (isPlainObject(srcValue) || isArguments(srcValue)) {
+ if (isArguments(objValue)) {
+ newValue = toPlainObject(objValue);
+ }
+ else if (!isObject(objValue) || (srcIndex && isFunction(objValue))) {
+ isCommon = false;
+ newValue = baseClone(srcValue);
+ }
+ else {
+ newValue = srcIndex ? baseClone(objValue) : objValue;
+ }
+ }
+ else {
+ isCommon = false;
+ }
+ }
+ stack.set(srcValue, newValue);
+
+ if (isCommon) {
+ // Recursively merge objects and arrays (susceptible to call stack limits).
+ mergeFunc(newValue, srcValue, srcIndex, customizer, stack);
+ }
+ assignMergeValue(object, key, newValue);
+}
+
+module.exports = baseMergeDeep;