recompute has-permissions helper on permission service attr change

ui/app/helpers/has-permission.js

@@ -1,8 +1,18 @@
 import Helper from '@ember/component/helper';
 import { inject as service } from '@ember/service';
+import { observer } from '@ember/object';
 
 export default Helper.extend({
   permissions: service(),
+  onPermissionsChange: observer(
+    'permissions.exactPaths',
+    'permissions.globPaths',
+    'permissions.canViewAll',
+    function() {
+      this.recompute();
+    }
+  ),
+
   compute([route], { routeParams, capability }) {
     let permissions = this.permissions;
     return permissions.hasNavPermission(route, routeParams, capability);

ui/tests/integration/helpers/has-permission-test.js

@@ -0,0 +1,31 @@
+import { module, test } from 'qunit';
+import { setupRenderingTest } from 'ember-qunit';
+import { render } from '@ember/test-helpers';
+import { run } from '@ember/runloop';
+import hbs from 'htmlbars-inline-precompile';
+import Service from '@ember/service';
+
+const Permissions = Service.extend({
+  globPaths: null,
+  hasNavPermission() {
+    return this.globPaths ? true : false;
+  },
+});
+
+module('Integration | Helper | has-permission', function(hooks) {
+  setupRenderingTest(hooks);
+  hooks.beforeEach(function() {
+    this.owner.register('service:permissions', Permissions);
+    this.permissions = this.owner.lookup('service:permissions');
+  });
+
+  test('it renders', async function(assert) {
+    await render(hbs`{{#if (has-permission)}}Yes{{else}}No{{/if}}`);
+
+    assert.equal(this.element.textContent.trim(), 'No');
+    await run(() => {
+      this.permissions.set('globPaths', { 'test/': { capabilities: ['update'] } });
+    });
+    assert.equal(this.element.textContent.trim(), 'Yes', 'the helper re-computes when globPaths changes');
+  });
+});