chore(router): clean up code and add comments (#23355)

core/src/components/router/router.tsx

@@ -2,6 +2,7 @@ import { Component, ComponentInterface, Element, Event, EventEmitter, Listen, Me
 
 import { AnimationBuilder, BackButtonEvent, RouteChain, RouterDirection, RouterEventDetail } from '../../interface';
 import { debounce } from '../../utils/helpers';
+import { NavigationHookResult } from '../route/route-interface';
 
 import { ROUTER_INTENT_BACK, ROUTER_INTENT_FORWARD, ROUTER_INTENT_NONE } from './utils/constants';
 import { printRedirects, printRoutes } from './utils/debug';
@@ -186,6 +187,7 @@ export class Router implements ComponentInterface {
     return true;
   }
 
+  // This handler gets called when a `ion-route-redirect` component is added to the DOM or if the from or to property of such node changes.
   private onRedirectChanged() {
     const path = this.getPath();
     if (path && findRouteRedirect(path, readRedirects(this.el))) {
@@ -193,6 +195,7 @@ export class Router implements ComponentInterface {
     }
   }
 
+  // This handler gets called when a `ion-route` component is added to the DOM or if the from or to property of such node changes.
   private onRoutesChanged() {
     return this.writeNavStateRoot(this.getPath(), ROUTER_INTENT_NONE);
   }
@@ -202,7 +205,7 @@ export class Router implements ComponentInterface {
 
     if (win.history.state === null) {
       this.state++;
-      win.history.replaceState(this.state, win.document.title, win.document.location && win.document.location.href);
+      win.history.replaceState(this.state, win.document.title, win.document.location?.href);
     }
 
     const state = win.history.state;
@@ -211,11 +214,11 @@ export class Router implements ComponentInterface {
 
     if (state > lastState || (state >= lastState && lastState > 0)) {
       return ROUTER_INTENT_FORWARD;
-    } else if (state < lastState) {
+    }
+    if (state < lastState) {
       return ROUTER_INTENT_BACK;
-    } else {
-      return ROUTER_INTENT_NONE;
     }
+    return ROUTER_INTENT_NONE;
   }
 
   private async writeNavStateRoot(path: string[] | null, direction: RouterDirection, animation?: AnimationBuilder): Promise<boolean> {
@@ -281,7 +284,7 @@ export class Router implements ComponentInterface {
   //
   // When the beforeLeave hook does not return true (to allow navigating) then that value is returned early and the beforeEnter is executed.
   // Otherwise the beforeEnterHook hook of the target route is executed.
-  private async runGuards(to: string[] | null = this.getPath(), from?: string[] | null) {
+  private async runGuards(to: string[] | null = this.getPath(), from?: string[] | null): Promise<NavigationHookResult> {
     if (from === undefined) {
       from = parsePath(this.previousPath).segments;
     }

core/src/components/router/utils/dom.ts

@@ -88,5 +88,5 @@ const searchNavNode = (root: HTMLElement | undefined): NavOutletElement | undefi
     return root as NavOutletElement;
   }
   const outlet = root.querySelector<NavOutletElement>(QUERY);
-  return outlet ? outlet : undefined;
+  return outlet ?? undefined;
 };

core/src/components/router/utils/parser.ts

@@ -1,6 +1,16 @@
 import { RouteChain, RouteNode, RouteRedirect, RouteTree } from './interface';
 import { parsePath } from './path';
 
+const readProp = (el: HTMLElement, prop: string): string | null | undefined => {
+  if (prop in el) {
+    return (el as any)[prop];
+  }
+  if (el.hasAttribute(prop)) {
+    return el.getAttribute(prop);
+  }
+  return null;
+};
+
 export const readRedirects = (root: Element): RouteRedirect[] => {
   return (Array.from(root.children) as HTMLIonRouteRedirectElement[])
     .filter(el => el.tagName === 'ION-ROUTE-REDIRECT')
@@ -17,46 +27,33 @@ export const readRoutes = (root: Element): RouteChain[] => {
   return flattenRouterTree(readRouteNodes(root));
 };
 
-export const readRouteNodes = (root: Element, node = root): RouteTree => {
+export const readRouteNodes = (node: Element): RouteTree => {
   return (Array.from(node.children) as HTMLIonRouteElement[])
     .filter(el => el.tagName === 'ION-ROUTE' && el.component)
     .map(el => {
-      const component = readProp(el, 'component');
-      if (component == null) {
-        throw new Error('component missing in ion-route');
-      }
+      const component = readProp(el, 'component') as string;
       return {
         path: parsePath(readProp(el, 'url')).segments,
         id: component.toLowerCase(),
         params: el.componentProps,
         beforeLeave: el.beforeLeave,
         beforeEnter: el.beforeEnter,
-        children: readRouteNodes(root, el)
+        children: readRouteNodes(el)
       };
     });
 };
 
-export const readProp = (el: HTMLElement, prop: string): string | null | undefined => {
-  if (prop in el) {
-    return (el as any)[prop];
-  }
-  if (el.hasAttribute(prop)) {
-    return el.getAttribute(prop);
-  }
-  return null;
-};
-
 export const flattenRouterTree = (nodes: RouteTree): RouteChain[] => {
-  const routes: RouteChain[] = [];
+  const chains: RouteChain[] = [];
   for (const node of nodes) {
-    flattenNode([], routes, node);
+    flattenNode([], chains, node);
   }
-  return routes;
+  return chains;
 };
 
-const flattenNode = (chain: RouteChain, routes: RouteChain[], node: RouteNode) => {
-  const s = chain.slice();
-  s.push({
+const flattenNode = (chain: RouteChain, chains: RouteChain[], node: RouteNode) => {
+  chain = chain.slice();
+  chain.push({
     id: node.id,
     path: node.path,
     params: node.params,
@@ -65,10 +62,10 @@ const flattenNode = (chain: RouteChain, routes: RouteChain[], node: RouteNode) =
   });
 
   if (node.children.length === 0) {
-    routes.push(s);
+    chains.push(chain);
     return;
   }
-  for (const sub of node.children) {
-    flattenNode(s, routes, sub);
+  for (const child of node.children) {
+    flattenNode(chain, chains, child);
   }
 };

core/src/components/router/utils/path.ts

@@ -1,6 +1,7 @@
 import { ROUTER_INTENT_FORWARD } from './constants';
 import { ParsedRoute, RouteChain, RouterDirection } from './interface';
 
+// Join the non empty segments with "/".
 export const generatePath = (segments: string[]): string => {
   const path = segments
     .filter(s => s.length > 0)
@@ -9,6 +10,26 @@ export const generatePath = (segments: string[]): string => {
   return '/' + path;
 };
 
+const generateUrl = (segments: string[], useHash: boolean, queryString?: string) => {
+  let url = generatePath(segments);
+  if (useHash) {
+    url = '#' + url;
+  }
+  if (queryString !== undefined) {
+    url += '?' + queryString;
+  }
+  return url;
+}
+
+export const writePath = (history: History, root: string, useHash: boolean, path: string[], direction: RouterDirection, state: number, queryString?: string) => {
+  const url = generateUrl([...parsePath(root).segments, ...path], useHash, queryString);
+  if (direction === ROUTER_INTENT_FORWARD) {
+    history.pushState(state, '', url);
+  } else {
+    history.replaceState(state, '', url);
+  }
+};
+
 export const chainToPath = (chain: RouteChain): string[] | null => {
   const path = [];
   for (const route of chain) {
@@ -27,25 +48,12 @@ export const chainToPath = (chain: RouteChain): string[] | null => {
   return path;
 };
 
-export const writePath = (history: History, root: string, useHash: boolean, path: string[], direction: RouterDirection, state: number, queryString?: string) => {
-  let url = generatePath([
-    ...parsePath(root).segments,
-    ...path
-  ]);
-  if (useHash) {
-    url = '#' + url;
-  }
-  if (queryString !== undefined) {
-    url = url + '?' + queryString;
-  }
-  if (direction === ROUTER_INTENT_FORWARD) {
-    history.pushState(state, '', url);
-  } else {
-    history.replaceState(state, '', url);
-  }
-};
-
-export const removePrefix = (prefix: string[], path: string[]): string[] | null => {
+// Remove the prefix segments from the path segments.
+//
+// Return:
+// - null when the path segments do not start with the passed prefix,
+// - the path segments after the prefix otherwise.
+const removePrefix = (prefix: string[], path: string[]): string[] | null => {
   if (prefix.length > path.length) {
     return null;
   }
@@ -53,7 +61,7 @@ export const removePrefix = (prefix: string[], path: string[]): string[] | null
     return path;
   }
   for (let i = 0; i < prefix.length; i++) {
-    if (prefix[i].length > 0 && prefix[i] !== path[i]) {
+    if (prefix[i] !== path[i]) {
       return null;
     }
   }
@@ -64,15 +72,8 @@ export const removePrefix = (prefix: string[], path: string[]): string[] | null
 };
 
 export const readPath = (loc: Location, root: string, useHash: boolean): string[] | null => {
-  let pathname = loc.pathname;
-  if (useHash) {
-    const hash = loc.hash;
-    pathname = (hash[0] === '#')
-      ? hash.slice(1)
-      : '';
-  }
-
   const prefix = parsePath(root).segments;
+  const pathname = useHash ? loc.hash.slice(1) : loc.pathname;
   const path = parsePath(pathname).segments;
   return removePrefix(prefix, path);
 };