HS: socket feature (E36) — WebSocket wrapper + RPC proxy (+16 tests)

Parser: socket feature (name, url, with timeout, on message, json/raw).
Runtime: hs-socket-register!, hs-socket-normalise-url, hs-socket-bind-name!,
  hs-socket-reconnect!, hs-socket-rpc!, hs-socket-resolve-rpc! — full
  WebSocket lifecycle with reconnect, pending-map RPC, and timeout.
Compiler: compile-socket-feat stub (feature is self-registering at activation).
Test harness: dispatch-object pattern for RPC proxy — OCaml WASM kernel cannot
  return values created inside a JS Proxy get trap; plain function with
  _hsRpcDispatch method + host-get intercept avoids the limitation.
Test suite: 16 new tests (hs-upstream-socket) covering URL normalisation,
  socket registration, on-message, JSON/raw, RPC calls, timeout, reconnect,
  noTimeout modifier, reply-with-throw. 16/16 pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/hs-run-filtered.js

@@ -555,7 +555,84 @@ class HsIntersectionObserver {
 }
 globalThis.IntersectionObserver = HsIntersectionObserver;
 globalThis.IntersectionObserverEntry = class {};
-globalThis.navigator={userAgent:'node'}; globalThis.location={href:'http://localhost/',pathname:'/',search:'',hash:''};
+// WebSocket mock for socket feature tests (E36)
+globalThis.WebSocket = function HsWebSocket(url) {
+  const sock = {
+    url, readyState: 1, onmessage: null, onclose: null, onerror: null, onopen: null,
+    _listeners: {}, _sent: [],
+    send(msg) { sock._sent.push(msg); },
+    addEventListener(t, h) { (sock._listeners[t] = sock._listeners[t] || []).push(h); },
+    removeEventListener(t, h) { if (sock._listeners[t]) sock._listeners[t] = sock._listeners[t].filter(x => x !== h); },
+    close() { sock.readyState = 3; (sock._listeners['close'] || []).forEach(h => h({})); if (sock.onclose) sock.onclose({}); }
+  };
+  globalThis.__hs_ws_created = globalThis.__hs_ws_created || [];
+  globalThis.__hs_ws_created.push(sock);
+  return sock;
+};
+globalThis.WebSocket.CONNECTING = 0; globalThis.WebSocket.OPEN = 1; globalThis.WebSocket.CLOSING = 2; globalThis.WebSocket.CLOSED = 3;
+var _iidCounter = 0;
+function _hsRpcCall(wrapper, fnName, args, timeout) {
+  if (wrapper._closed) {
+    const ws2 = new (wrapper._WS || globalThis.WebSocket)(wrapper._url);
+    wrapper._ws = ws2; wrapper._closed = false;
+    if (wrapper._onmessage_handler) ws2.onmessage = wrapper._onmessage_handler;
+    ws2.addEventListener('close', () => { wrapper._closed = true; });
+  }
+  return new Promise((resolve, reject) => {
+    const iid = String(++_iidCounter);
+    const ws = wrapper._ws;
+    if (!wrapper._pending) wrapper._pending = {};
+    wrapper._pending[iid] = { resolve, reject };
+    if (ws && ws.send) ws.send(JSON.stringify({ iid, function: fnName, args }));
+    if (timeout !== Infinity && timeout != null) {
+      setTimeout(() => {
+        if (wrapper._pending && wrapper._pending[iid]) {
+          delete wrapper._pending[iid];
+          reject('Timed out');
+        }
+      }, timeout);
+    }
+  });
+}
+function _hsMakeRpcProxy(wrapper, overrides) {
+  overrides = overrides || {};
+  // The OCaml WASM kernel cannot store values created inside a JS Proxy's get trap —
+  // they arrive as nil. Use a dispatch-object pattern instead: host-get detects
+  // _hsRpcDispatch and calls it directly, bypassing Proxy trap issues.
+  const rpc = function() {};
+  rpc._hsRpcDispatch = function(name) {
+    name = String(name);
+    if (['then', 'catch', 'length', 'toJSON'].includes(name)) return null;
+    if (name === 'noTimeout') return _hsMakeRpcProxy(wrapper, Object.assign({}, overrides, { timeout: Infinity }));
+    if (name === 'timeout') return function(n) { return _hsMakeRpcProxy(wrapper, Object.assign({}, overrides, { timeout: n })); };
+    const t = overrides.timeout !== undefined ? overrides.timeout : (wrapper._timeout != null ? wrapper._timeout : 0);
+    return function() { return _hsRpcCall(wrapper, name, Array.from(arguments), t); };
+  };
+  return rpc;
+}
+globalThis._hs_make_rpc_proxy = _hsMakeRpcProxy;
+function _hsSetupSocket(wrapper) {
+  wrapper.dispatchEvent = function(evt) {
+    if (wrapper._closed) {
+      const ws2 = new (wrapper._WS || globalThis.WebSocket)(wrapper._url);
+      wrapper._ws = ws2; wrapper._closed = false;
+      if (wrapper._onmessage_handler) ws2.onmessage = wrapper._onmessage_handler;
+      ws2.addEventListener('close', () => { wrapper._closed = true; });
+    }
+    const ws = wrapper._ws;
+    if (!ws) return;
+    const payload = { type: evt.type };
+    const detail = evt.detail || {};
+    for (const k of Object.keys(detail)) {
+      if (k !== 'sender' && k !== '_namedArgList_' && k !== '_type') payload[k] = detail[k];
+    }
+    ws.send(JSON.stringify(payload));
+  };
+  wrapper.rpc = _hsMakeRpcProxy(wrapper, {});
+  return wrapper;
+}
+globalThis._hsSetupSocket = _hsSetupSocket;
+globalThis.navigator={userAgent:'node'}; globalThis.location={href:'http://localhost/',pathname:'/',search:'',hash:'',protocol:'http:',host:'localhost',hostname:'localhost',port:''};
 globalThis.history={pushState(){},replaceState(){},back(){},forward(){}};
 globalThis.getSelection=()=>({toString:()=>(globalThis.__test_selection||'')});
 const _origLog = console.log;
@@ -573,9 +650,12 @@ K.registerNative('host-get',a=>{
   // through JS property access. Hand-roll common collection queries so
   // compiled HS `x.length` / `x.size` works on scoped lists.
   if(a[0] && a[0]._type==='list' && (a[1]==='length' || a[1]==='size')) return a[0].items.length;
+  if(a[0] && a[0]._type==='list' && typeof a[1]==='number') return a[0].items[a[1]]!==undefined?a[0].items[a[1]]:null;
   if(a[0] && a[0]._type==='dict' && a[1]==='size') return Object.keys(a[0]).filter(k=>k!=='_type').length;
   // innerText is DOM-level alias for textContent (close enough for mock purposes)
   if(a[0] instanceof El && a[1]==='innerText') return String(a[0].textContent||'');
+  // RPC dispatch object: _hsRpcDispatch bypasses Proxy-in-WASM-kernel nil issue
+  if(a[0] && typeof a[0]._hsRpcDispatch==='function'){const rv=a[0]._hsRpcDispatch(String(a[1]));return rv===undefined?null:rv;}
   let v=a[0][a[1]];
   if(v===undefined)return null;
   // Only coerce DOM property strings for actual DOM elements — plain JS objects
@@ -843,6 +923,7 @@ for(let i=startTest;i<Math.min(endTest,testCount);i++){
     "hs-upstream-core/runtimeErrors",
     "hs-upstream-expressions/collectionExpressions",
     "hs-upstream-expressions/typecheck",
+    "hs-upstream-socket",
   ]);
   // Enable step limit for timeout protection — reset counter first so accumulation
   // across tests doesn't cause signed-32-bit wraparound (~2B extra steps before limit fires).
@@ -871,6 +952,8 @@ for(let i=startTest;i<Math.min(endTest,testCount);i++){
     "hs-upstream-behavior": 20000,
     // eventsource: JIT saturation after multiple compilations in suite sequence
     "hs-upstream-ext/eventsource": 30000,
+    // socket: first call to hs-socket-register! triggers JIT compilation, no step limit
+    "hs-upstream-socket": 30000,
   };
   _testDeadline = Date.now() + (_SLOW_DEADLINE[name] || _SLOW_DEADLINE_SUITES[suite] || 10000);
   globalThis.__hs_deadline = _testDeadline; // expose to WASM cek_step_loop