docs: explain why route id can be null (#13581)

* .

* Revert "."

This reverts commit be452ea.

* update public.d.ts

---------

Co-authored-by: Rich Harris <[email protected]>

Author: sacrosanctic

packages/kit/src/exports/public.d.ts

@@ -990,7 +990,7 @@ export interface NavigationEvent<
 	 */
 	route: {
 		/**
-		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`
+		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
 		 */
 		id: RouteId;
 	};
@@ -1012,7 +1012,12 @@ export interface NavigationTarget {
 	/**
 	 * Info about the target route
 	 */
-	route: { id: string | null };
+	route: {
+		/**
+		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
+		 */
+		id: string | null;
+	};
 	/**
 	 * The URL that is navigated to
 	 */
@@ -1129,7 +1134,7 @@ export interface Page<
 	 */
 	route: {
 		/**
-		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`.
+		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
 		 */
 		id: RouteId;
 	};
@@ -1205,7 +1210,7 @@ export interface RequestEvent<
 	 */
 	route: {
 		/**
-		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`.
+		 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
 		 */
 		id: RouteId;
 	};

packages/kit/types/index.d.ts

@@ -972,7 +972,7 @@ declare module '@sveltejs/kit' {
 		 */
 		route: {
 			/**
-			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`
+			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
 			 */
 			id: RouteId;
 		};
@@ -994,7 +994,12 @@ declare module '@sveltejs/kit' {
 		/**
 		 * Info about the target route
 		 */
-		route: { id: string | null };
+		route: {
+			/**
+			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
+			 */
+			id: string | null;
+		};
 		/**
 		 * The URL that is navigated to
 		 */
@@ -1111,7 +1116,7 @@ declare module '@sveltejs/kit' {
 		 */
 		route: {
 			/**
-			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`.
+			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
 			 */
 			id: RouteId;
 		};
@@ -1187,7 +1192,7 @@ declare module '@sveltejs/kit' {
 		 */
 		route: {
 			/**
-			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`.
+			 * The ID of the current route - e.g. for `src/routes/blog/[slug]`, it would be `/blog/[slug]`. It is `null` when no route is matched.
 			 */
 			id: RouteId;
 		};