From db01158d2d9830293ff55ea26f56851b4abe97ca Mon Sep 17 00:00:00 2001
From: Karl Seguin <k@openmymind.io>
Date: Thu, 19 Mar 2026 11:36:39 +0800
Subject: [PATCH] Improve unhandled rejection

We now pay attention to the type of event that causes the unhandled exception.
This allows us to trigger the window.rejectionhandled event when that is the
correct type. It also lets us no-op for other event types which should not
trigger rejectionhandled or unhandledrejection.

Fixes stackoverflow in github integration.
---
 src/browser/js/Env.zig        |  7 ++++++-
 src/browser/webapi/Window.zig | 27 ++++++++++++++++++++++-----
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/src/browser/js/Env.zig b/src/browser/js/Env.zig
index 09117eb0..d1aed2cc 100644
--- a/src/browser/js/Env.zig
+++ b/src/browser/js/Env.zig
@@ -495,6 +495,11 @@ pub fn terminate(self: *const Env) void {
 }
 
 fn promiseRejectCallback(message_handle: v8.PromiseRejectMessage) callconv(.c) void {
+    const promise_event = v8.v8__PromiseRejectMessage__GetEvent(&message_handle);
+    if (promise_event != v8.kPromiseRejectWithNoHandler and promise_event != v8.kPromiseHandlerAddedAfterReject) {
+        return;
+    }
+
     const promise_handle = v8.v8__PromiseRejectMessage__GetPromise(&message_handle).?;
     const v8_isolate = v8.v8__Object__GetIsolate(@ptrCast(promise_handle)).?;
     const isolate = js.Isolate{ .handle = v8_isolate };
@@ -508,7 +513,7 @@ fn promiseRejectCallback(message_handle: v8.PromiseRejectMessage) callconv(.c) v
     };
 
     const page = ctx.page;
-    page.window.unhandledPromiseRejection(.{
+    page.window.unhandledPromiseRejection(promise_event == v8.kPromiseRejectWithNoHandler, .{
         .local = &local,
         .handle = &message_handle,
     }, page) catch |err| {
diff --git a/src/browser/webapi/Window.zig b/src/browser/webapi/Window.zig
index d3a8ebfc..bbed1010 100644
--- a/src/browser/webapi/Window.zig
+++ b/src/browser/webapi/Window.zig
@@ -67,7 +67,8 @@ _on_pageshow: ?js.Function.Global = null,
 _on_popstate: ?js.Function.Global = null,
 _on_error: ?js.Function.Global = null,
 _on_message: ?js.Function.Global = null,
-_on_unhandled_rejection: ?js.Function.Global = null, // TODO: invoke on error
+_on_rejection_handled: ?js.Function.Global = null,
+_on_unhandled_rejection: ?js.Function.Global = null,
 _current_event: ?*Event = null,
 _location: *Location,
 _timer_id: u30 = 0,
@@ -222,6 +223,14 @@ pub fn setOnMessage(self: *Window, setter: ?FunctionSetter) void {
     self._on_message = getFunctionFromSetter(setter);
 }
 
+pub fn getOnRejectionHandled(self: *const Window) ?js.Function.Global {
+    return self._on_rejection_handled;
+}
+
+pub fn setOnRejectionHandled(self: *Window, setter: ?FunctionSetter) void {
+    self._on_rejection_handled = getFunctionFromSetter(setter);
+}
+
 pub fn getOnUnhandledRejection(self: *const Window) ?js.Function.Global {
     return self._on_unhandled_rejection;
 }
@@ -572,7 +581,7 @@ pub fn scrollBy(self: *Window, opts: ScrollToOpts, y: ?i32, page: *Page) !void {
     return self.scrollTo(.{ .x = absx }, absy, page);
 }
 
-pub fn unhandledPromiseRejection(self: *Window, rejection: js.PromiseRejection, page: *Page) !void {
+pub fn unhandledPromiseRejection(self: *Window, no_handler: bool, rejection: js.PromiseRejection, page: *Page) !void {
     if (comptime IS_DEBUG) {
         log.debug(.js, "unhandled rejection", .{
             .value = rejection.reason(),
@@ -580,13 +589,20 @@ pub fn unhandledPromiseRejection(self: *Window, rejection: js.PromiseRejection,
         });
     }
 
+    const event_name, const attribute_callback = blk: {
+        if (no_handler) {
+            break :blk .{ "unhandledrejection", self._on_unhandled_rejection };
+        }
+        break :blk .{ "rejectionhandled", self._on_rejection_handled };
+    };
+
     const target = self.asEventTarget();
-    if (page._event_manager.hasDirectListeners(target, "unhandledrejection", self._on_unhandled_rejection)) {
-        const event = (try @import("event/PromiseRejectionEvent.zig").init("unhandledrejection", .{
+    if (page._event_manager.hasDirectListeners(target, event_name, attribute_callback)) {
+        const event = (try @import("event/PromiseRejectionEvent.zig").init(event_name, .{
             .reason = if (rejection.reason()) |r| try r.temp() else null,
             .promise = try rejection.promise().temp(),
         }, page)).asEvent();
-        try page._event_manager.dispatchDirect(target, event, self._on_unhandled_rejection, .{ .context = "window.unhandledrejection" });
+        try page._event_manager.dispatchDirect(target, event, attribute_callback, .{ .context = "window.unhandledrejection" });
     }
 }
 
@@ -813,6 +829,7 @@ pub const JsApi = struct {
     pub const onpopstate = bridge.accessor(Window.getOnPopState, Window.setOnPopState, .{});
     pub const onerror = bridge.accessor(Window.getOnError, Window.setOnError, .{});
     pub const onmessage = bridge.accessor(Window.getOnMessage, Window.setOnMessage, .{});
+    pub const onrejectionhandled = bridge.accessor(Window.getOnRejectionHandled, Window.setOnRejectionHandled, .{});
     pub const onunhandledrejection = bridge.accessor(Window.getOnUnhandledRejection, Window.setOnUnhandledRejection, .{});
     pub const event = bridge.accessor(Window.getEvent, null, .{ .null_as_undefined = true });
     pub const fetch = bridge.function(Window.fetch, .{});