refactor(@angular-devkit/schematics): use self-closing tag for router-outlet

Let's make the component as simple a possible.

Author: JeanMeche

packages/schematics/angular/app-shell/index.ts

@@ -31,7 +31,7 @@ import { applyToUpdateRecorder } from '../utility/change';
 import { getAppModulePath, isStandaloneApp } from '../utility/ng-ast-utils';
 import { getMainFilePath } from '../utility/standalone/util';
 import { getWorkspace, updateWorkspace } from '../utility/workspace';
-import { Builders, ServerBuilderOptions } from '../utility/workspace-models';
+import { Builders } from '../utility/workspace-models';
 import { Schema as AppShellOptions } from './schema';
 
 const APP_SHELL_ROUTE = 'shell';
@@ -130,7 +130,7 @@ function getBootstrapComponentPath(host: Tree, mainPath: string): string {
 
 function validateProject(mainPath: string): Rule {
   return (host: Tree) => {
-    const routerOutletCheckRegex = /<router-outlet.*?>([\s\S]*?)<\/router-outlet>/;
+    const routerOutletCheckRegex = /<router-outlet.*?>([\s\S]*?)(?:<\/router-outlet>)?/;
 
     const componentPath = getBootstrapComponentPath(host, mainPath);
     const tmpl = getComponentTemplateInfo(host, componentPath);

packages/schematics/angular/application/files/common-files/src/app/app.component.html.template

@@ -333,4 +333,4 @@
 <!-- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -->
 
 <% if (routing) { %>
-<router-outlet></router-outlet><% } %>
+<router-outlet /><% } %>

packages/schematics/angular/application/files/module-files/src/app/app.component.ts.template

@@ -6,7 +6,7 @@ import { Component } from '@angular/core';
     <h1>Welcome to {{title}}!</h1>
 
     <% if (routing) {
-     %><router-outlet></router-outlet><%
+     %><router-outlet /><%
     } %>
   `,<% } else { %>
   templateUrl: './app.component.html',<% } if(inlineStyle) { %>