Only compute gathered middleware once

src/Illuminate/Routing/Route.php

@@ -74,6 +74,13 @@ class Route
      */
     public $parameterNames;
 
+    /**
+     * The computed gathered middleware.
+     *
+     * @var array|null
+     */
+    public $computedMiddleware;
+
     /**
      * The compiled version of the route.
      *
@@ -659,9 +666,19 @@ public function setAction(array $action)
      */
     public function gatherMiddleware()
     {
-        return array_unique(array_merge(
+        if (! is_null($this->computedMiddleware)) {
+            return $this->computedMiddleware;
+        }
+
+        // Set incase of an exception, so next time this
+        // method is called, the exception is not rethrown.
+        $this->computedMiddleware = [];
+
+        $this->computedMiddleware = array_unique(array_merge(
             $this->middleware(), $this->controllerMiddleware()
         ), SORT_REGULAR);
+
+        return $this->computedMiddleware;
     }
 
     /**