From ac710784aff2ada5b3dd2aa0d3179aa41763faf5 Mon Sep 17 00:00:00 2001
From: Even Oscar Andersen <even.oscar.andersen@qt.io>
Date: Sat, 17 May 2025 08:06:38 +0200
Subject: [PATCH] wasm: Handle exceptions in promise
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Fixes: QTBUG-136962
Change-Id: I2d33b0132a83945b476f0f47fa4697ddaa2374b3
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
---
 src/corelib/platform/wasm/qstdweb.cpp      | 11 ++++++++---
 tests/manual/wasm/qstdweb/promise_main.cpp | 23 ++++++++++++++++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/src/corelib/platform/wasm/qstdweb.cpp b/src/corelib/platform/wasm/qstdweb.cpp
index 18ab0ec1a9c..727668c45ae 100644
--- a/src/corelib/platform/wasm/qstdweb.cpp
+++ b/src/corelib/platform/wasm/qstdweb.cpp
@@ -487,10 +487,15 @@ void Promise::adoptPromise(emscripten::val promise, PromiseCallbacks callbacks)
 
     // Set handlers on the promise
     if (thenIndex)
-        promise.call<emscripten::val>("then", suspendResume->jsEventHandlerAt(*thenIndex));
+        promise =
+                promise.call<emscripten::val>("then", suspendResume->jsEventHandlerAt(*thenIndex));
+
     if (catchIndex)
-        promise.call<emscripten::val>("catch", suspendResume->jsEventHandlerAt(*catchIndex));
-    promise.call<emscripten::val>("finally", suspendResume->jsEventHandlerAt(*finallyIndex));
+        promise = promise.call<emscripten::val>("catch",
+                                                suspendResume->jsEventHandlerAt(*catchIndex));
+
+    promise = promise.call<emscripten::val>("finally",
+                                            suspendResume->jsEventHandlerAt(*finallyIndex));
 }
 
 void Promise::all(std::vector<emscripten::val> promises, PromiseCallbacks callbacks)
diff --git a/tests/manual/wasm/qstdweb/promise_main.cpp b/tests/manual/wasm/qstdweb/promise_main.cpp
index 5f1e5102c93..395e815cf95 100644
--- a/tests/manual/wasm/qstdweb/promise_main.cpp
+++ b/tests/manual/wasm/qstdweb/promise_main.cpp
@@ -54,6 +54,7 @@ private slots:
     void multipleResolve();
     void simpleReject();
     void multipleReject();
+    void throwInThen();
     void bareFinally();
     void finallyWithThen();
     void finallyWithThrow();
@@ -188,6 +189,28 @@ void WasmPromiseTest::multipleReject()
     }, promiseCount);
 }
 
+void WasmPromiseTest::throwInThen()
+{
+    init();
+
+    qstdweb::Promise::make(m_testSupport, "makeTestPromise", {
+        .thenFunc = [](val result) {
+            Q_UNUSED(result);
+            EM_ASM({
+                throw "Expected error";
+            });
+        },
+        .catchFunc = [](val error) {
+            QWASMCOMPARE("Expected error", error.as<std::string>());
+            QWASMSUCCESS();
+         }
+    }, std::string("throwInThen"));
+
+    EM_ASM({
+        testSupport.resolve["throwInThen"]();
+    });
+}
+
 void WasmPromiseTest::bareFinally()
 {
     init();