fix initial spa render of 404 errors (#3980)

Co-authored-by: mrkishi <[email protected]>

Author: Rich-Harris

packages/kit/src/runtime/client/renderer.js

@@ -496,6 +496,14 @@ export class Renderer {
 			);
 			if (result) return result;
 		}
+
+		if (info.initial) {
+			return await this._load_error({
+				status: 404,
+				error: new Error(`Not found: ${info.url.pathname}`),
+				url: info.url
+			});
+		}
 	}
 
 	/**

packages/kit/src/runtime/client/router.js

@@ -51,6 +51,7 @@ export class Router {
 		renderer.router = this;
 
 		this.enabled = true;
+		this.initialized = false;
 
 		// make it possible to reset focus
 		document.body.setAttribute('tabindex', '-1');
@@ -252,6 +253,8 @@ export class Router {
 				);
 			}
 		});
+
+		this.initialized = true;
 	}
 
 	/**
@@ -274,7 +277,8 @@ export class Router {
 				id: url.pathname + url.search,
 				routes: this.routes.filter(([pattern]) => pattern.test(path)),
 				url,
-				path
+				path,
+				initial: !this.initialized
 			};
 		}
 	}

packages/kit/src/runtime/client/types.d.ts

@@ -5,6 +5,7 @@ export type NavigationInfo = {
 	routes: CSRRoute[];
 	url: URL;
 	path: string;
+	initial: boolean;
 };
 
 export type NavigationCandidate = {