server-app: make _sortLayersByPhase stable

Fix the phase-sorting algorithm to use a stable sorting algorithm,
since the built-in `Array.prototype.sort` is not stable.

lib/server-app.js

@@ -3,6 +3,7 @@ var express = require('express');
 var merge = require('util')._extend;
 var mergePhaseNameLists = require('loopback-phase').mergePhaseNameLists;
 var debug = require('debug')('loopback:app');
+var stableSortInPlace = require('stable').inplace;
 
 var BUILTIN_MIDDLEWARE = { builtin: true };
 
@@ -214,7 +215,7 @@ proto._sortLayersByPhase = function() {
   });
 
   var router = this._router;
-  router.stack.sort(compareLayers);
+  stableSortInPlace(router.stack, compareLayers);
 
   function compareLayers(left, right) {
     var leftPhase = left.phase;

package.json

@@ -46,6 +46,7 @@
     "nodemailer": "~1.3.0",
     "nodemailer-stub-transport": "~0.1.4",
     "serve-favicon": "^2.1.6",
+    "stable": "^0.1.5",
     "strong-remoting": "^2.4.0",
     "uid2": "0.0.3",
     "underscore.string": "~2.3.3"

test/app.test.js

@@ -239,6 +239,26 @@ describe('app', function() {
       });
     });
 
+    it('preserves order of middleware in the same phase', function(done) {
+      // while we are discouraging developers from depending on
+      // the registration order of middleware in the same phase,
+      // we must preserve the order for compatibility with `app.use`
+      // and `app.route`.
+
+      // we need at least 9 elements to expose non-stability
+      // of the built-in sort function
+      var numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+      numbers.forEach(function(n) {
+        app.middleware('routes', namedHandler(n));
+      });
+
+      executeMiddlewareHandlers(app, function(err) {
+        if (err) return done;
+        expect(steps).to.eql(numbers);
+        done();
+      });
+    });
+
     it('correctly mounts express apps', function(done) {
       var data;
       var mountWasEmitted;