feat(wasm): execute client handlers without requests

req: client_local/001\nreq: client_local/004\nreq: client_local/005\nreq: client_local/009\nreq: client_local/010\nreq: client_local/014\nreq: v1_release/001

hemx-js/runtime/hemx.d.ts

@@ -54,6 +54,7 @@ export interface HemxRuntime {
   decodeBatch(buffer: ArrayBuffer): EffectBatch;
   atomValue(root: Element | ParentNode | null | undefined, id: number): Uint8Array | undefined;
   decodeAtomState(encoded: string): AtomSnapshot[];
+  registerClientHandler(name: string, handler: () => Uint8Array | Promise<Uint8Array>): void;
 }
 
 declare global {

hemx-js/runtime/hemx.js

@@ -18,6 +18,7 @@
   const sseSources = new WeakMap();
   const atomStores = new WeakMap();
   const dragKeys = new WeakMap();
+  const clientHandlers = new Map();
 
   function roots() {
     const found = [];
@@ -237,6 +238,15 @@
     });
   }
 
+  async function runClient(el) {
+    const name = el.getAttribute("data-hemx-client");
+    const handler = clientHandlers.get(name);
+    if (!handler) throw new Error(`unknown client-local hemx handler: ${name}`);
+    const wire = await handler();
+    if (!(wire instanceof Uint8Array)) throw new Error(`client-local hemx handler ${name} returned an invalid effect batch`);
+    applyBatch(wire, rootOf(el));
+  }
+
   async function send(el, eventName, source = el) {
     if (el.getAttribute("data-hemx-confirm") && !confirm(el.getAttribute("data-hemx-confirm"))) return;
     const { form, data, multipart } = formDataFor(el, eventName, source);
@@ -671,7 +681,11 @@
           const direct = closestInRoot(event.target, root, (el) => el.hasAttribute(HID));
           if (direct && defaultEvent(direct) === "click") {
             event.preventDefault();
-            schedule(direct, name);
+            if (direct.hasAttribute("data-hemx-client")) {
+              runClient(direct).catch((error) => emit(root, "hemx:client-error", String(error)));
+            } else {
+              schedule(direct, name);
+            }
             return;
           }
         }
@@ -935,7 +949,20 @@
     if (root) navigateUrl(location.href, root, "none").catch((error) => emit(root, "hemx:error", String(error)));
   });
 
-  window.hemx = Object.freeze({ runtimeAbiVersion, roots, rootOf, applyHtml, applyBatch, decodeBatch, atomValue, decodeAtomState });
+  window.hemx = Object.freeze({
+    runtimeAbiVersion,
+    roots,
+    rootOf,
+    applyHtml,
+    applyBatch,
+    decodeBatch,
+    atomValue,
+    decodeAtomState,
+    registerClientHandler(name, handler) {
+      if (!name || typeof handler !== "function") throw new Error("client handler registration requires a name and function");
+      clientHandlers.set(name, handler);
+    },
+  });
 
   if (document.readyState === "loading") document.addEventListener("DOMContentLoaded", start);
   else start();