Fix bug where param handlers were run out of order

lib/layer.js

@@ -170,29 +170,24 @@ Layer.prototype.param = function (param, fn) {
   };
   middleware.param = param;
 
-  params.forEach(function (p, i) {
-    var prev = params[i - 1];
-
-    if (param === p.name) {
-      // insert param middleware in order params appear in path
-      if (prev) {
-        if (!stack.some(function (m, i) {
-          if (m.param === prev.name) {
-            return stack.splice(i, 0, middleware);
-          }
-        })) {
-          stack.some(function (m, i) {
-            if (!m.param) {
-              return stack.splice(i, 0, middleware);
-            }
-          });
-        }
-      } else {
-        stack.unshift(middleware);
-      }
-    }
+  var names = params.map(function (p) {
+    return p.name;
   });
 
+  var x = names.indexOf(param);
+  if (x > -1) {
+    // iterate through the stack, to figure out where to place the handler fn
+    stack.some(function (fn, i) {
+      // param handlers are always first, so when we find an fn w/o a param property, stop here
+      // if the param handler at this part of the stack comes after the one we are adding, stop here
+      if (!fn.param || names.indexOf(fn.param) > x) {
+        // inject this param handler right before the current item
+        stack.splice(i, 0, middleware);
+        return true; // then break the loop
+      }
+    });
+  }
+
   return this;
 };
 

test/lib/router.js

@@ -1047,6 +1047,45 @@ describe('Router', function() {
     });
 
     it('runs parameter middleware in order of URL appearance', function(done) {
+      var app = koa();
+      var router = new Router();
+      router
+        .param('first', function *(id, next) {
+          this.ranFirst = true;
+          if (this.user) {
+            this.ranFirst = false;
+          }
+          if (!id) return this.status = 404;
+          yield next;
+        })
+        .param('user', function *(id, next) {
+          this.user = { name: 'alex' };
+          if (this.ranFirst) {
+            this.user.ordered = 'parameters';
+          }
+          if (!id) return this.status = 404;
+          yield next;
+        })
+        .get('/:first/users/:user', function *(next) {
+          this.body = this.user;
+        });
+
+      request(http.createServer(
+        app
+          .use(router.routes())
+          .callback()))
+      .get('/first/users/3')
+      .expect(200)
+      .end(function(err, res) {
+        if (err) return done(err);
+        res.should.have.property('body');
+        res.body.should.have.property('name', 'alex');
+        res.body.should.have.property('ordered', 'parameters');
+        done();
+      });
+    });
+
+    it('runs parameter middleware in order of URL appearance even when added in reverse order', function(done) {
       var app = koa();
       var router = new Router();
       router
@@ -1085,6 +1124,45 @@ describe('Router', function() {
       });
     });
 
+    it('runs parameter middleware in order of URL appearance even when added in random order', function(done) {
+      var app = koa();
+      var router = new Router();
+      router
+        // intentional random order
+        .param('a', function *(id, next) {
+          this.state.loaded = [ id ];
+          yield next;
+        })
+        .param('d', function *(id, next) {
+          this.state.loaded.push(id);
+          yield next;
+        })
+        .param('c', function *(id, next) {
+          this.state.loaded.push(id);
+          yield next;
+        })
+        .param('b', function *(id, next) {
+          this.state.loaded.push(id);
+          yield next;
+        })
+        .get('/:a/:b/:c/:d', function *(next) {
+          this.body = this.state.loaded;
+        });
+
+      request(http.createServer(
+        app
+          .use(router.routes())
+          .callback()))
+      .get('/1/2/3/4')
+      .expect(200)
+      .end(function(err, res) {
+        if (err) return done(err);
+        res.should.have.property('body');
+        res.body.should.eql([ '1', '2', '3', '4' ]);
+        done();
+      });
+    });
+
     it('runs parent parameter middleware for subrouter', function (done) {
       var app = koa();
       var router = new Router();