fix: Pass ctx.props to default handlers

Author: tewaro

src/workerd/api/global-scope.h

@@ -382,6 +382,35 @@ struct ExportedHandler {
   jsg::Optional<jsg::Ref<ExecutionContext>> getCtx() {
     return ctx.map([&](jsg::Ref<ExecutionContext>& p) { return p.addRef(); });
   }
+
+  template <typename T>
+  static jsg::LenientOptional<T> ADDREF(jsg::LenientOptional<T>& function, jsg::Lock& js) {
+    return function.map([&](T& a) { return a.addRef(js); });
+  }
+
+#define CLONE(x)                                                                                   \
+  .x {                                                                                             \
+    ADDREF(x, js)                                                                                  \
+  }
+
+  ExportedHandler clone(jsg::Lock& js) {
+    return ExportedHandler{
+      CLONE(fetch),
+      CLONE(tail),
+      CLONE(trace),
+      CLONE(tailStream),
+      CLONE(scheduled),
+      CLONE(alarm),
+      CLONE(test),
+      CLONE(webSocketMessage),
+      CLONE(webSocketClose),
+      CLONE(webSocketError),
+      .self{js.v8Isolate, v8::Object::New(js.v8Isolate)},
+      .env{env.addRef(js)},
+      .ctx{getCtx()},
+      .missingSuperclass = missingSuperclass,
+    };
+  }
 };
 
 // An approximation of Node.js setImmediate `Immediate` object.

src/workerd/io/compatibility-date.capnp

@@ -692,4 +692,9 @@ struct CompatibilityFlags @0x8f8c1b68151b6cef {
       $experimental
       $neededByFl;
   # Enables cache settings specified request in fetch api cf object to override cache rules. (only for user owned or grey-clouded sites)
+
+  uniqueCtxPerInvocation @73: Bool
+      $compatEnableFlag("unique_ctx_per_invocation")
+      $compatDisableFlag("nonclass_entrypoint_reuses_ctx_accros_invocations")
+      $compatEnableDate("2025-02-24");
 }

src/workerd/io/worker.c++

@@ -1971,7 +1971,15 @@ kj::Maybe<kj::Own<api::ExportedHandler>> Worker::Lock::getExportedHandler(
 
   kj::StringPtr n = name.orDefault("default"_kj);
   KJ_IF_SOME(h, worker.impl->namedHandlers.find(n)) {
-    return fakeOwn(h);
+    kj::Own<api::ExportedHandler> ret = fakeOwn(h);
+    jsg::Lock& js = *this;
+    if (FeatureFlags::get(js).getUniqueCtxPerInvocation()) {
+      api::ExportedHandler constructedHandler = h.clone(js);
+      constructedHandler.ctx = jsg::alloc<api::ExecutionContext>(js, props.toJs(js));
+      kj::Own<api::ExportedHandler> handlerPtr = kj::heap(kj::mv(constructedHandler));
+      return handlerPtr;
+    }
+    return ret;
   } else KJ_IF_SOME(cls, worker.impl->statelessClasses.find(n)) {
     jsg::Lock& js = *this;
     auto handler = kj::heap(cls(js, jsg::alloc<api::ExecutionContext>(js, props.toJs(js)),