fix: restore routerLoad argument to createHandler (#2228)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: brenelz

.changeset/spotty-moons-repeat.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/start": patch
+---
+
+Restore the optional `routerLoad` third argument to `createHandler`, which primes custom routers (e.g. TanStack Router) on the server before SSR rendering. It was accidentally dropped in the v2 rewrite.

packages/start/src/server/handler.ts

@@ -21,6 +21,7 @@ export function createBaseHandler(
   createPageEvent: (e: FetchEvent) => Promise<PageEvent>,
   fn: (context: PageEvent) => JSX.Element,
   options: HandlerOptions | ((context: PageEvent) => HandlerOptions | Promise<HandlerOptions>) = {},
+  routerLoad?: (event: FetchEvent) => Promise<void>,
 ): H3 {
   const handler = defineHandler({
     middleware: middleware.length ? middleware.map(decorateMiddleware) : undefined,
@@ -64,6 +65,8 @@ export function createBaseHandler(
         }
       }
 
+      if (routerLoad) await routerLoad(event);
+
       const context = await createPageEvent(event);
 
       const resolvedOptions =
@@ -134,8 +137,9 @@ export function createBaseHandler(
 export function createHandler(
   fn: (context: PageEvent) => JSX.Element,
   options: HandlerOptions | ((context: PageEvent) => HandlerOptions | Promise<HandlerOptions>) = {},
+  routerLoad?: (event: FetchEvent) => Promise<void>,
 ): H3 {
-  return createBaseHandler(createPageEvent, fn, options);
+  return createBaseHandler(createPageEvent, fn, options, routerLoad);
 }
 
 export async function createPageEvent(ctx: FetchEvent) {

packages/start/src/server/spa/handler.ts

@@ -12,8 +12,9 @@ import type { FetchEvent, HandlerOptions, PageEvent } from "../types.ts";
 export function createHandler(
   fn: (context: PageEvent) => JSX.Element,
   options?: HandlerOptions | ((context: PageEvent) => HandlerOptions),
+  routerLoad?: (event: FetchEvent) => Promise<void>,
 ): H3 {
-  return createBaseHandler(createPageEvent, fn, options);
+  return createBaseHandler(createPageEvent, fn, options, routerLoad);
 }
 
 async function createPageEvent(ctx: FetchEvent) {