[BUGFIX beta] sets the controller _qpDelegate

before mapping all the queryParams.

In certain scenarios, if query params are shared
through a service, bound query params will
fire the _qpDelegate while transitioning to a new
controller if the property has been modified from
it's default value.

Loosely related to
  - #11592

  Based on a previous PR
    - #13981

packages/ember-routing/lib/system/route.js

@@ -1316,6 +1316,9 @@ let Route = EmberObject.extend(ActionHandler, Evented, {
     let queryParams = get(this, '_qp');
 
     let states = queryParams.states;
+
+    controller._qpDelegate = states.allowOverrides;
+
     if (transition) {
       // Update the model dep values used to calculate cache keys.
       stashParamNames(this.router, transition.state.handlerInfos);
@@ -1337,8 +1340,6 @@ let Route = EmberObject.extend(ActionHandler, Evented, {
       });
     }
 
-    controller._qpDelegate = states.allowOverrides;
-
     if (transition) {
       let qpValues = getQueryParamsFor(this, transition.state);
       controller.setProperties(qpValues);

packages/ember/tests/routing/query_params_test/shared_state_test.js

@@ -0,0 +1,76 @@
+import {
+  Controller,
+  Service
+} from 'ember-runtime';
+import Ember from 'ember';
+import { run } from 'ember-metal';
+import { jQuery } from 'ember-views';
+import { QueryParamTestCase, moduleFor } from 'internal-test-helpers';
+
+moduleFor('Query Params - shared service state', class extends QueryParamTestCase {
+
+  boot() {
+    this.setupApplication();
+    return this.visitApplication();
+  }
+
+  setupApplication() {
+    this.router.map(function() {
+      this.route('home', { path: '/' });
+      this.route('dashboard');
+    });
+
+    this.application.register('service:filters', Service.extend({
+      shared: true
+    }));
+
+    this.registerController('home', Controller.extend({
+      filters: Ember.inject.service()
+    }));
+
+    this.registerController('dashboard', Controller.extend({
+      filters: Ember.inject.service(),
+      queryParams: [
+        { 'filters.shared': 'shared' }
+      ]
+    }));
+
+    this.registerTemplate('application', `{{link-to 'Home' 'home' }} <div> {{outlet}} </div>`);
+    this.registerTemplate('home', `{{link-to 'Dashboard' 'dashboard' }}{{input type="checkbox" id='filters-checkbox' checked=(mut filters.shared) }}`);
+    this.registerTemplate('dashboard', `{{link-to 'Home' 'home' }}`);
+  }
+  visitApplication() {
+    return this.visit('/');
+  }
+
+  ['@test can modify shared state before transition'](assert) {
+    assert.expect(1);
+
+    return this.boot().then(() => {
+      this.$input = jQuery('#filters-checkbox');
+
+      // click the checkbox once to set filters.shared to false
+      run(this.$input, 'click');
+
+      return this.visit('/dashboard').then(() => {
+        assert.ok(true, 'expecting navigating to dashboard to succeed');
+      });
+    });
+  }
+
+  ['@test can modify shared state back to the default value before transition'](assert) {
+    assert.expect(1);
+
+    return this.boot().then(() => {
+      this.$input = jQuery('#filters-checkbox');
+
+      // click the checkbox twice to set filters.shared to false and back to true
+      run(this.$input, 'click');
+      run(this.$input, 'click');
+
+      return this.visit('/dashboard').then(() => {
+        assert.ok(true, 'expecting navigating to dashboard to succeed');
+      });
+    });
+  }
+});