Closes #1, prevent next from being executed more than once.

lib/conditional.js

@@ -1,3 +1,5 @@
+var once = require('once');
+
 /**
  * Returns a middleware that can be used to conditionally execute another
  * middleware, or alternatively bypass it.
@@ -27,6 +29,7 @@
  */
 module.exports = function (condition, middleware) {
   return function (req, res, next) {
+    next = once(next);
     if (condition === true || (typeof condition === 'function' && condition(req, res, next))) {
       return middleware(req, res, next);
     }

package.json

@@ -23,5 +23,8 @@
       "pre-commit": "gulp lint",
       "pre-push": "gulp test"
     }
+  },
+  "dependencies": {
+    "once": "^1.3.2"
   }
 }

test/index.js

@@ -51,6 +51,31 @@ module.exports = {
       test.ok(true, 'Conditional function returned false.');
       test.done();
     });
+  },
+
+  funcOnce: function (test) {
+    test.expect(2);
+
+    var count = 0;
+
+    var conditionFunc = function (req, res, next) {
+      next();
+      return true;
+    };
+
+    var middleware = conditional(
+      conditionFunc,
+      function (req, res, next) {
+        test.ok(true, 'Conditional executed.');
+        next();
+        test.done();
+      }
+    );
+
+    middleware({}, {}, function () {
+      count++;
+      test.equal(count, 1, 'Middleware only executed once.');
+    });
   }
 };