Introduce a default routing state

In case the current state is the default one we don't redirect.
This gets rid of the initial redirect/histroy entry when loading the page.

packages/app-shell/src/app-shell.js

@@ -228,6 +228,12 @@ export class AppShell extends ScopedElementsMixin(DBPLitElement) {
             setState: (state) => {
                 this.updateLangIfChanged(state.lang);
                 this.switchComponent(state.component);
+            },
+            getDefaultState: () => {
+                return {
+                    lang: 'de',
+                    component: this.routes[0],
+                };
             }
         }, {
             baseUrl: new URL(this.basePath, window.location).pathname.replace(/\/$/, ''),

packages/app-shell/src/router.js

@@ -17,12 +17,14 @@ export class Router {
     constructor(routes, options, unioptions) {
         this.getState = options.getState;
         this.setState = options.setState;
+        this.getDefaultState = options.getDefaultState;
         // XXX: We only have one route atm
         // If we need more we need to pass the route name to each function
         this.routeName = options.routeName;
 
         console.assert(this.getState);
         console.assert(this.setState);
+        console.assert(this.getDefaultState);
         console.assert(this.routeName);
 
         // https://github.com/kriasoft/universal-router
@@ -39,6 +41,7 @@ export class Router {
      */
     setStateFromCurrentLocation() {
         const oldPathName = location.pathname;
+
         this.router.resolve({pathname: oldPathName}).then(page => {
             const newPathname = this.getPathname(page);
             // In case of a router redirect, set the new location
@@ -46,6 +49,8 @@ export class Router {
                 const referrerUrl = location.href;
                 window.history.replaceState({}, '', newPathname);
                 this.dispatchLocationChanged(referrerUrl);
+            } else if (this.isBasePath(oldPathName)) {
+                page = this.getDefaultState();
             }
             this.setState(page);
         }).catch((e) => {
@@ -54,6 +59,10 @@ export class Router {
         });
     }
 
+    isBasePath(pathname) {
+        return pathname.replace(/\/$/, '') === this.router.baseUrl.replace(/\/$/, '');
+    }
+
     /**
      * Update the router after some internal state change.
      */
@@ -65,6 +74,12 @@ export class Router {
             const oldPathname = location.pathname;
             if (newPathname === oldPathname)
                 return;
+
+            const defaultPathname = this.getPathname(this.getDefaultState());
+            if (newPathname === defaultPathname && this.isBasePath(oldPathname)) {
+                return;
+            }
+
             const referrerUrl = location.href;
             window.history.pushState({}, '', newPathname);
             this.dispatchLocationChanged(referrerUrl);

packages/app-shell/test/unit.js

@@ -19,6 +19,7 @@ suite('router', () => {
       routeName: 'foo',
       getState: () => { return {}; },
       setState: (state) => { },
+      getDefaultState: () => { return {}; },
     });
 
     router.setStateFromCurrentLocation();