LibJS: Add side-effect-free version of Value::to_string()

There are now two API's on Value:

- Value::to_string(Interpreter&) -- may throw.
- Value::to_string_without_side_effects() -- will never throw.

These are some pretty big sweeping changes, so it's possible that I did
some part the wrong way. We'll work it out as we go. :^)

Fixes #2123.

Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.cpp

@@ -161,8 +161,12 @@ JS::Value CanvasRenderingContext2DWrapper::fill_style_getter(JS::Interpreter& in
 
 void CanvasRenderingContext2DWrapper::fill_style_setter(JS::Interpreter& interpreter, JS::Value value)
 {
-    if (auto* impl = impl_from(interpreter))
-        impl->set_fill_style(value.to_string());
+    if (auto* impl = impl_from(interpreter)) {
+        auto string = value.to_string(interpreter);
+        if (interpreter.exception())
+            return;
+        impl->set_fill_style(string);
+    }
 }
 
 JS::Value CanvasRenderingContext2DWrapper::stroke_style_getter(JS::Interpreter& interpreter)
@@ -175,8 +179,12 @@ JS::Value CanvasRenderingContext2DWrapper::stroke_style_getter(JS::Interpreter&
 
 void CanvasRenderingContext2DWrapper::stroke_style_setter(JS::Interpreter& interpreter, JS::Value value)
 {
-    if (auto* impl = impl_from(interpreter))
-        impl->set_stroke_style(value.to_string());
+    if (auto* impl = impl_from(interpreter)){
+        auto string = value.to_string(interpreter);
+        if (interpreter.exception())
+            return;
+        impl->set_stroke_style(string);
+    }
 }
 
 JS::Value CanvasRenderingContext2DWrapper::line_width_getter(JS::Interpreter& interpreter)

Libraries/LibWeb/Bindings/DocumentWrapper.cpp

@@ -78,7 +78,9 @@ JS::Value DocumentWrapper::get_element_by_id(JS::Interpreter& interpreter)
     auto& arguments = interpreter.call_frame().arguments;
     if (arguments.is_empty())
         return JS::js_null();
-    auto id = arguments[0].to_string();
+    auto id = arguments[0].to_string(interpreter);
+    if (interpreter.exception())
+        return {};
     auto* element = document->get_element_by_id(id);
     if (!element)
         return JS::js_null();
@@ -93,7 +95,9 @@ JS::Value DocumentWrapper::query_selector_all(JS::Interpreter& interpreter)
     auto& arguments = interpreter.call_frame().arguments;
     if (arguments.is_empty())
         return JS::js_null();
-    auto selector = arguments[0].to_string();
+    auto selector = arguments[0].to_string(interpreter);
+    if (interpreter.exception())
+        return {};
     auto elements = document->query_selector_all(selector);
     // FIXME: This should be a static NodeList, not a plain JS::Array.
     auto* node_list = JS::Array::create(interpreter.global_object());

Libraries/LibWeb/Bindings/ElementWrapper.cpp

@@ -74,8 +74,12 @@ JS::Value ElementWrapper::inner_html_getter(JS::Interpreter& interpreter)
 
 void ElementWrapper::inner_html_setter(JS::Interpreter& interpreter, JS::Value value)
 {
-    if (auto* impl = impl_from(interpreter))
-        impl->set_inner_html(value.to_string());
+    if (auto* impl = impl_from(interpreter)) {
+        auto string = value.to_string(interpreter);
+        if (interpreter.exception())
+            return;
+        impl->set_inner_html(string);
+    }
 }
 
 JS::Value ElementWrapper::id_getter(JS::Interpreter& interpreter)
@@ -87,8 +91,12 @@ JS::Value ElementWrapper::id_getter(JS::Interpreter& interpreter)
 
 void ElementWrapper::id_setter(JS::Interpreter& interpreter, JS::Value value)
 {
-    if (auto* impl = impl_from(interpreter))
-        impl->set_attribute("id", value.to_string());
+    if (auto* impl = impl_from(interpreter)) {
+        auto string = value.to_string(interpreter);
+        if (interpreter.exception())
+            return;
+        impl->set_attribute("id", string);
+    }
 }
 
 }

Libraries/LibWeb/Bindings/EventTargetWrapper.cpp

@@ -56,7 +56,9 @@ JS::Value EventTargetWrapper::add_event_listener(JS::Interpreter& interpreter)
     auto& arguments = interpreter.call_frame().arguments;
     if (arguments.size() < 2)
         return JS::js_undefined();
-    auto event_name = arguments[0].to_string();
+    auto event_name = arguments[0].to_string(interpreter);
+    if (interpreter.exception())
+        return {};
     ASSERT(arguments[1].is_object());
     ASSERT(arguments[1].as_object().is_function());
     auto& function = static_cast<JS::Function&>(const_cast<Object&>(arguments[1].as_object()));

Libraries/LibWeb/Bindings/HTMLCanvasElementWrapper.cpp

@@ -76,7 +76,10 @@ JS::Value HTMLCanvasElementWrapper::get_context(JS::Interpreter& interpreter)
         return {};
     auto& arguments = interpreter.call_frame().arguments;
     if (arguments.size() >= 1) {
-        auto* context = impl->get_context(arguments[0].to_string());
+        auto string = arguments[0].to_string(interpreter);
+        if (interpreter.exception())
+            return {};
+        auto* context = impl->get_context(string);
         return wrap(interpreter.heap(), *context);
     }
     return JS::js_undefined();

Libraries/LibWeb/Bindings/WindowObject.cpp

@@ -98,8 +98,11 @@ JS::Value WindowObject::alert(JS::Interpreter& interpreter)
     if (!impl)
         return {};
     String message = "";
-    if (interpreter.argument_count())
-        message = interpreter.argument(0).to_string();
+    if (interpreter.argument_count()) {
+        message = interpreter.argument(0).to_string(interpreter);
+        if (interpreter.exception())
+            return {};
+    }
     impl->alert(message);
     return JS::js_undefined();
 }
@@ -110,8 +113,11 @@ JS::Value WindowObject::confirm(JS::Interpreter& interpreter)
     if (!impl)
         return {};
     String message = "";
-    if (interpreter.argument_count())
-        message = interpreter.argument(0).to_string();
+    if (interpreter.argument_count()) {
+        message = interpreter.argument(0).to_string(interpreter);
+        if (interpreter.exception())
+            return {};
+    }
     return JS::Value(impl->confirm(message));
 }
 

Libraries/LibWeb/Bindings/XMLHttpRequestPrototype.cpp

@@ -71,7 +71,13 @@ JS::Value XMLHttpRequestPrototype::open(JS::Interpreter& interpreter)
     auto* impl = impl_from(interpreter);
     if (!impl)
         return {};
-    impl->open(interpreter.argument(0).to_string(), interpreter.argument(1).to_string());
+    auto arg0 = interpreter.argument(0).to_string(interpreter);
+    if (interpreter.exception())
+        return {};
+    auto arg1 = interpreter.argument(1).to_string(interpreter);
+    if (interpreter.exception())
+        return {};
+    impl->open(arg0, arg1);
     return JS::js_undefined();
 }