LibJS+LibWeb: Clear exceptions after call'ing JavaScript functions

Decorated Interpreter::call() with [[nodiscard]] to provoke thinking
about the returned value at each call site. This is definitely not
perfect and we should really start thinking about slimming down the
public-facing LibJS interpreter API.

Fixes #3136.

6 files changed, 18 insertions, 7 deletions

diff --git a/Libraries/LibJS/Interpreter.h b/Libraries/LibJS/Interpreter.h
index 99b011e213..b18c490a79 100644
--- a/Libraries/LibJS/Interpreter.h
+++ b/Libraries/LibJS/Interpreter.h
@@ -118,7 +118,7 @@ public:
     void enter_scope(const ScopeNode&, ArgumentVector, ScopeType, GlobalObject&);
     void exit_scope(const ScopeNode&);
 
-    Value call(Function&, Value this_value, Optional<MarkedValueList> arguments = {});
+    [[nodiscard]] Value call(Function&, Value this_value, Optional<MarkedValueList> arguments = {});
     Value construct(Function&, Function& new_target, Optional<MarkedValueList> arguments, GlobalObject&);
 
     CallFrame& push_call_frame()
diff --git a/Libraries/LibJS/Runtime/Accessor.h b/Libraries/LibJS/Runtime/Accessor.h
index 115a405ffa..612472e27e 100644
--- a/Libraries/LibJS/Runtime/Accessor.h
+++ b/Libraries/LibJS/Runtime/Accessor.h
@@ -65,7 +65,8 @@ public:
             return;
         MarkedValueList arguments(interpreter().heap());
         arguments.append(setter_value);
-        interpreter().call(*m_setter, this_value, move(arguments));
+        // FIXME: It might be nice if we had a way to communicate to our caller if an exception happened after this.
+        (void)interpreter().call(*m_setter, this_value, move(arguments));
     }
 
     void visit_children(Cell::Visitor& visitor) override
diff --git a/Libraries/LibJS/Runtime/Object.cpp b/Libraries/LibJS/Runtime/Object.cpp
index b026dff3be..d5797deec4 100644
--- a/Libraries/LibJS/Runtime/Object.cpp
+++ b/Libraries/LibJS/Runtime/Object.cpp
@@ -737,7 +737,7 @@ bool Object::put(const PropertyName& property_name, Value value, Value receiver)
         }
         object = object->prototype();
         if (interpreter().exception())
-            return {};
+            return false;
     }
     return put_own_property(*this, string_or_symbol, value, default_attributes, PutOwnPropertyMode::Put);
 }
diff --git a/Libraries/LibWeb/DOM/Node.cpp b/Libraries/LibWeb/DOM/Node.cpp
index b6a51ddfe2..0b8cc49b4d 100644
--- a/Libraries/LibWeb/DOM/Node.cpp
+++ b/Libraries/LibWeb/DOM/Node.cpp
@@ -127,7 +127,10 @@ void Node::dispatch_event(NonnullRefPtr<Event> event)
             auto* event_wrapper = wrap(global_object, *event);
             JS::MarkedValueList arguments(global_object.heap());
             arguments.append(event_wrapper);
-            document().interpreter().call(function, this_value, move(arguments));
+            auto& interpreter = document().interpreter();
+            (void)interpreter.call(function, this_value, move(arguments));
+            if (interpreter.exception())
+                interpreter.clear_exception();
         }
     }
 
diff --git a/Libraries/LibWeb/DOM/Window.cpp b/Libraries/LibWeb/DOM/Window.cpp
index 965812574e..4314432c09 100644
--- a/Libraries/LibWeb/DOM/Window.cpp
+++ b/Libraries/LibWeb/DOM/Window.cpp
@@ -94,7 +94,9 @@ void Window::timer_did_fire(Badge<Timer>, Timer& timer)
     }
 
     auto& interpreter = wrapper()->interpreter();
-    interpreter.call(timer.callback(), wrapper());
+    (void)interpreter.call(timer.callback(), wrapper());
+    if (interpreter.exception())
+        interpreter.clear_exception();
 }
 
 i32 Window::allocate_timer_id(Badge<Timer>)
@@ -123,7 +125,9 @@ i32 Window::request_animation_frame(JS::Function& callback)
         JS::MarkedValueList arguments(interpreter.heap());
         arguments.append(JS::Value(fake_timestamp));
         fake_timestamp += 10;
-        interpreter.call(function, {}, move(arguments));
+        (void)interpreter.call(function, {}, move(arguments));
+        if (interpreter.exception())
+            interpreter.clear_exception();
         GUI::DisplayLink::unregister_callback(link_id);
     });
 
diff --git a/Libraries/LibWeb/DOM/XMLHttpRequest.cpp b/Libraries/LibWeb/DOM/XMLHttpRequest.cpp
index 6dcf43dde7..b75d272701 100644
--- a/Libraries/LibWeb/DOM/XMLHttpRequest.cpp
+++ b/Libraries/LibWeb/DOM/XMLHttpRequest.cpp
@@ -98,7 +98,10 @@ void XMLHttpRequest::dispatch_event(NonnullRefPtr<DOM::Event> event)
             auto* this_value = wrap(global_object, *this);
             JS::MarkedValueList arguments(global_object.heap());
             arguments.append(wrap(global_object, *event));
-            function.interpreter().call(function, this_value, move(arguments));
+            auto& interpreter = function.interpreter();
+            (void)interpreter.call(function, this_value, move(arguments));
+            if (interpreter.exception())
+                interpreter.clear_exception();
         }
     }
 }