Fix _.mixin creates functions that respect __chain__.

lodash.js

@@ -586,8 +586,8 @@
     /*--------------------------------------------------------------------------*/
 
     /**
-     * Creates a `lodash` object which wraps the given value to enable method
-     * chaining.
+     * Creates a `lodash` object which wraps the given value to enable intuitive
+     * method chaining.
      *
      * In addition to Lo-Dash methods, wrappers also have the following `Array` methods:
      * `concat`, `join`, `pop`, `push`, `reverse`, `shift`, `slice`, `sort`, `splice`,
@@ -621,6 +621,8 @@
      * The wrapper functions `first` and `last` return wrapped values when `n` is
      * provided, otherwise they return unwrapped values.
      *
+     * Explicit chaining can be enabled by using the `_.chain` method.
+     *
      * @name _
      * @constructor
      * @category Chaining
@@ -5916,9 +5918,12 @@
 
             push.apply(args, arguments);
             var result = func.apply(object, args);
-            return (value && typeof value == 'object' && value === result)
-              ? this
-              : new ctor(result);
+            if (value && typeof value == 'object' && value === result) {
+              return this;
+            }
+            result = new ctor(result);
+            result.__chain__ = this.__chain__;
+            return result;
           };
         }
       });
@@ -6320,7 +6325,8 @@
     /*--------------------------------------------------------------------------*/
 
     /**
-     * Creates a `lodash` object that wraps the given value.
+     * Creates a `lodash` object that wraps the given value with explicit
+     * method chaining enabled.
      *
      * @static
      * @memberOf _
@@ -6336,9 +6342,10 @@
      * ];
      *
      * var youngest = _.chain(stooges)
-     *     .sortBy(function(stooge) { return stooge.age; })
+     *     .sortBy('age')
      *     .map(function(stooge) { return stooge.name + ' is ' + stooge.age; })
-     *     .first();
+     *     .first()
+     *     .value();
      * // => 'moe is 40'
      */
     function chain(value) {
@@ -6375,7 +6382,7 @@
     }
 
     /**
-     * Enables method chaining on the wrapper object.
+     * Enables explicit method chaining on the wrapper object.
      *
      * @name chain
      * @memberOf _
@@ -6383,11 +6390,21 @@
      * @returns {*} Returns the wrapper object.
      * @example
      *
-     * var sum = _([1, 2, 3])
-     *     .chain()
-     *     .reduce(function(sum, num) { return sum + num; })
-     *     .value()
-     * // => 6`
+     * var stooges = [
+     *   { 'name': 'moe', 'age': 40 },
+     *   { 'name': 'larry', 'age': 50 }
+     * ];
+     *
+     * // without explicit chaining
+     * _(stooges).first();
+     * // => { 'name': 'moe', 'age': 40 }
+     *
+     * // with explicit chaining
+     * _(stooges).chain()
+     *   .first()
+     *   .pick('age')
+     *   .value()
+     * // => { 'age': 40 }
      */
     function wrapperChain() {
       this.__chain__ = true;