From e47b1cc1a2d3c059b211ba31bcfe4be86b6b121a Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Wed, 18 Jun 2025 08:36:30 +0200
Subject: [PATCH] LibCore: Accept any Promise<T> in Promise::after()

---
 Libraries/LibCore/Promise.h | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/Libraries/LibCore/Promise.h b/Libraries/LibCore/Promise.h
index f3de87e798e..47e927e7ff6 100644
--- a/Libraries/LibCore/Promise.h
+++ b/Libraries/LibCore/Promise.h
@@ -24,7 +24,8 @@ public:
     Function<ErrorOr<void>(Result&)> on_resolution;
     Function<void(ErrorType&)> on_rejection;
 
-    static NonnullRefPtr<Promise> after(Vector<NonnullRefPtr<Promise>>&& promises)
+    template<typename U>
+    static NonnullRefPtr<Promise> after(Vector<NonnullRefPtr<Promise<U>>> promises)
     {
         auto promise = Promise::construct();
         struct Resolved : RefCounted<Resolved> {
@@ -35,24 +36,32 @@ public:
 
             size_t count { 0 };
             size_t needed { 0 };
+            Optional<Error> error;
         };
 
         auto resolved = make_ref_counted<Resolved>(promises.size());
         auto weak_promise = promise->template make_weak_ptr<Promise>();
         for (auto p : promises) {
-            p->when_resolved([weak_promise, resolved](Result&) -> ErrorOr<void> {
+            p->when_resolved([weak_promise, resolved](auto&&) -> ErrorOr<void> {
                 if (!weak_promise || weak_promise->is_rejected())
                     return {};
 
-                if (++resolved->count == resolved->needed)
-                    weak_promise->resolve({});
+                if (++resolved->count == resolved->needed) {
+                    if (resolved->error.has_value())
+                        weak_promise->reject(resolved->error.release_value());
+                    else
+                        weak_promise->resolve({});
+                }
                 return {};
             });
 
-            p->when_rejected([weak_promise, resolved](ErrorType& error) {
-                ++resolved->count;
-                if (weak_promise)
-                    weak_promise->reject(move(error));
+            p->when_rejected([weak_promise, resolved](auto&& error) {
+                resolved->error = move(error);
+                if (!weak_promise)
+                    return;
+
+                if (++resolved->count == resolved->needed)
+                    weak_promise->reject(resolved->error.release_value());
             });
 
             promise->add_child(*p);