From e91a662491146da1c25e25e4da234c8bcafd00b3 Mon Sep 17 00:00:00 2001
From: Nicolas Chambrier <naholyr@gmail.com>
Date: Sat, 7 Feb 2015 20:28:34 +0100
Subject: [PATCH] Add _.spread.

---
 lodash.src.js | 40 ++++++++++++++++++++++++++++++++++++++++
 test/test.js  | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/lodash.src.js b/lodash.src.js
index 404872129..dbe7c46d1 100644
--- a/lodash.src.js
+++ b/lodash.src.js
@@ -7579,6 +7579,45 @@
       return createWrapper(func, REARG_FLAG, null, null, null, indexes);
     }
 
+    /**
+     * Creates a function accepting an array as argument, that invokes `func`
+     * with arguments taken from this array, like `Function#apply`.
+     * This works obviously well with `Promise.all`.
+     *
+     * @static
+     * @memberOf _
+     * @category Function
+     * @param {Function} The function to alter.
+     * @param {*} [thisArg] The `this` binding of `func`.
+     * @returns {*} Returns the new function.
+     * @example
+     *
+     * var spread = _.spread(function (who, what) {
+     *   return who + ' says ' + what;
+     * });
+     *
+     * spread(['John', 'hello']) // => 'John says hello'
+     *
+     * // With Promise
+     * var numbers = Promise.all([
+     *   Promise.resolve(42),
+     *   Promise.resolve(33)
+     * ])
+     *
+     * numbers.then(_.spread(function (a, b) { return a + b })) // Promise of 75
+     * // instead of...
+     * numbers.then(function (nums) { return nums[0] + nums[1] })
+     */
+    function spread (func, thisArg) {
+      if (typeof func !== 'function') {
+        throw new TypeError(FUNC_ERROR_TEXT);
+      }
+
+      return function(array) {
+        return func.apply(thisArg, array);
+      };
+    }
+
     /**
      * Creates a function that only invokes `func` at most once per every `wait`
      * milliseconds. The created function comes with a `cancel` method to cancel
@@ -10752,6 +10791,7 @@
     lodash.slice = slice;
     lodash.sortBy = sortBy;
     lodash.sortByAll = sortByAll;
+    lodash.spread = spread;
     lodash.take = take;
     lodash.takeRight = takeRight;
     lodash.takeRightWhile = takeRightWhile;
diff --git a/test/test.js b/test/test.js
index afeab682f..03b30c98f 100644
--- a/test/test.js
+++ b/test/test.js
@@ -12240,6 +12240,53 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.spread');
+
+  (function() {
+    function Pair(x, y) {
+      this.x = x;
+      this.y = y;
+
+      return 42;
+    }
+
+    function divide(n, d) {
+      return n / d;
+    }
+
+    test('should pass arguments to `func`', 1, function() {
+      var spread = _.spread(divide);
+      strictEqual(spread([4, 2]), 2);
+    });
+
+    test('should fail when receiving non-array argument', 1, function() {
+      var spread = _.spread(divide);
+      var err;
+      try {
+        spread(4, 2);
+      } catch (e) {
+        err = e;
+      }
+      strictEqual(_.isError(err), true);
+    });
+
+    test('should dynamically `func` to `thisArg`', 2, function() {
+      var self = {z: 3};
+      var spread = _.spread(Pair, self);
+      var result = spread([1, 2]);
+      strictEqual(result, 42);
+      deepEqual(self, {x: 1, y: 2, z: 3});
+    });
+
+    test('should use `undefined` for extra values', 1, function() {
+      var self = {};
+      _.spread(Pair, self)([1]);
+      deepEqual(self, {x: 1, y: undefined});
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.support');
 
   (function() {
@@ -14960,6 +15007,7 @@
       'partial',
       'partialRight',
       'rearg',
+      'spread',
       'throttle'
     ];
 
@@ -15078,7 +15126,7 @@
       });
     });
 
-    test('should throw an error for falsey arguments', 22, function() {
+    test('should throw an error for falsey arguments', 23, function() {
       _.each(rejectFalsey, function(methodName) {
         var expected = _.map(falsey, _.constant(true)),
             func = _[methodName];