Move internal modules to “internal” folder.

.internal/baseMergeDeep.js

@@ -0,0 +1,92 @@
+import assignMergeValue from './.internal/assignMergeValue.js';
+import cloneBuffer from './.internal/cloneBuffer.js';
+import cloneTypedArray from './.internal/cloneTypedArray.js';
+import copyArray from './.internal/copyArray.js';
+import initCloneObject from './.internal/initCloneObject.js';
+import isArguments from './isArguments.js';
+import isArrayLikeObject from './isArrayLikeObject.js';
+import isBuffer from './isBuffer.js';
+import isFunction from './isFunction.js';
+import isObject from './isObject.js';
+import isPlainObject from './isPlainObject.js';
+import isTypedArray from './isTypedArray.js';
+import toPlainObject from './toPlainObject.js';
+
+/**
+ * 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) {
+  const objValue = object[key];
+  const srcValue = source[key];
+  const stacked = stack.get(srcValue);
+
+  if (stacked) {
+    assignMergeValue(object, key, stacked);
+    return;
+  }
+  let newValue = customizer
+    ? customizer(objValue, srcValue, `${ key }`, object, source, stack)
+    : undefined;
+
+  let isCommon = newValue === undefined;
+
+  if (isCommon) {
+    const isArr = Array.isArray(srcValue);
+    const isBuff = !isArr && isBuffer(srcValue);
+    const isTyped = !isArr && !isBuff && isTypedArray(srcValue);
+
+    newValue = srcValue;
+    if (isArr || isBuff || isTyped) {
+      if (Array.isArray(objValue)) {
+        newValue = objValue;
+      }
+      else if (isArrayLikeObject(objValue)) {
+        newValue = copyArray(objValue);
+      }
+      else if (isBuff) {
+        isCommon = false;
+        newValue = cloneBuffer(srcValue, true);
+      }
+      else if (isTyped) {
+        isCommon = false;
+        newValue = cloneTypedArray(srcValue, true);
+      }
+      else {
+        newValue = [];
+      }
+    }
+    else if (isPlainObject(srcValue) || isArguments(srcValue)) {
+      newValue = objValue;
+      if (isArguments(objValue)) {
+        newValue = toPlainObject(objValue);
+      }
+      else if (!isObject(objValue) || (srcIndex && isFunction(objValue))) {
+        newValue = initCloneObject(srcValue);
+      }
+    }
+    else {
+      isCommon = false;
+    }
+  }
+  if (isCommon) {
+    // Recursively merge objects and arrays (susceptible to call stack limits).
+    stack.set(srcValue, newValue);
+    mergeFunc(newValue, srcValue, srcIndex, customizer, stack);
+    stack['delete'](srcValue);
+  }
+  assignMergeValue(object, key, newValue);
+}
+
+export default baseMergeDeep;