Fix _.mixin creates functions that respect __chain__.

dist/lodash.underscore.js

@@ -206,8 +206,8 @@
   /*--------------------------------------------------------------------------*/
 
   /**
-   * 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`,
@@ -241,6 +241,8 @@
    * 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
@@ -4146,11 +4148,9 @@
         push.apply(args, arguments);
 
         var result = func.apply(lodash, args);
-        if (this.__chain__) {
-          result = new lodashWrapper(result);
-          result.__chain__ = true;
-        }
-        return result;
+        return this.__chain__
+          ? new lodashWrapper(result, true)
+          : result;
       };
     });
   }
@@ -4467,7 +4467,8 @@
   /*--------------------------------------------------------------------------*/
 
   /**
-   * 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 _
@@ -4483,9 +4484,10 @@
    * ];
    *
    * 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) {
@@ -4522,7 +4524,7 @@
   }
 
   /**
-   * Enables method chaining on the wrapper object.
+   * Enables explicit method chaining on the wrapper object.
    *
    * @name chain
    * @memberOf _
@@ -4530,11 +4532,21 @@
    * @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;