Bugfixes. Documentation update.

src/functions/server/handle-hmr.ts

@@ -17,6 +17,7 @@ export default async function ({ req }: Params): Promise<Response> {
         : undefined;
 
     let controller: ReadableStreamDefaultController<string>;
+    let heartbeat: ReturnType<typeof setInterval>;
     const stream = new ReadableStream<string>({
         start(c) {
             controller = c;
@@ -25,8 +26,16 @@ export default async function ({ req }: Params): Promise<Response> {
                 page_url: referer_url.href,
                 target_map,
             });
+            heartbeat = setInterval(() => {
+                try {
+                    c.enqueue(": keep-alive\n\n");
+                } catch {
+                    clearInterval(heartbeat);
+                }
+            }, 5000);
         },
         cancel() {
+            clearInterval(heartbeat);
             const targetControllerIndex = global.HMR_CONTROLLERS.findIndex(
                 (c) => c.controller == controller,
             );

src/functions/server/web-pages/grab-web-page-hydration-script.tsx

@@ -28,6 +28,7 @@ export default async function (params?: Params) {
     script += `window.addEventListener("unhandledrejection", (e) => __bunext_show_error(String(e.reason?.message ?? e.reason), "", e.reason?.stack ?? ""));\n\n`;
 
     script += `const hmr = new EventSource("/__hmr");\n`;
+    script += `window.BUNEXT_HMR = hmr;\n`;
     script += `window.addEventListener("beforeunload", () => hmr.close());\n`;
     script += `hmr.addEventListener("update", async (event) => {\n`;
     script += `    if (event?.data) {\n`;