refactor `CGClassConstructHook` to use handwritten constructors (#33614)

* extract generated class constructor hook into handwritten functions

Signed-off-by: Gae24 <96017547+Gae24@users.noreply.github.com>

* downcast to window only when it's actually used

Signed-off-by: Gae24 <96017547+Gae24@users.noreply.github.com>

* simplify downcast

Signed-off-by: Gae24 <96017547+Gae24@users.noreply.github.com>

* rename htmlconstructor to constructor, include call_default_constructor in it

Signed-off-by: Gae24 <96017547+Gae24@users.noreply.github.com>

---------

Signed-off-by: Gae24 <96017547+Gae24@users.noreply.github.com>

4 files changed, 65 insertions, 40 deletions

diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 246e12b16ad..9cffaf35f93 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -6229,16 +6229,11 @@ class CGClassConstructHook(CGAbstractExternMethod):
 let args = CallArgs::from_vp(vp, argc);
 let global = GlobalScope::from_object(JS_CALLEE(*cx, vp).to_object());
 """
-        if len(self.exposureSet) == 1:
-            preamble += f"""
-let global = DomRoot::downcast::<dom::types::{list(self.exposureSet)[0]}>(global).unwrap();
-"""
         if self.constructor.isHTMLConstructor():
             signatures = self.constructor.signatures()
             assert len(signatures) == 1
-            constructorCall = CGGeneric(
-                f"""
-                dom::bindings::htmlconstructor::call_html_constructor::<dom::types::{self.descriptor.name}>(
+            constructorCall = f"""
+                call_html_constructor::<dom::types::{self.descriptor.name}>(
                     cx,
                     &args,
                     &global,
@@ -6246,34 +6241,39 @@ let global = DomRoot::downcast::<dom::types::{list(self.exposureSet)[0]}>(global
                     CreateInterfaceObjects,
                 )
                 """
-            )
         else:
             ctorName = GetConstructorNameForReporting(self.descriptor, self.constructor)
-            preamble += f"""
-if !args.is_constructing() {{
-  throw_constructor_without_new(*cx, "{ctorName}");
-  return false;
-}}
-
-rooted!(in(*cx) let mut desired_proto = ptr::null_mut::<JSObject>());
-let proto_result = get_desired_proto(
-  cx,
-  &args,
-  PrototypeList::ID::{MakeNativeName(self.descriptor.name)},
-  CreateInterfaceObjects,
-  desired_proto.handle_mut(),
-);
-assert!(proto_result.is_ok());
-if proto_result.is_err() {{
-  return false;
-}}
-"""
             name = self.constructor.identifier.name
             nativeName = MakeNativeName(self.descriptor.binaryNameFor(name))
-            args = ["&global", "Some(desired_proto.handle())", "CanGc::note()"]
-            constructorCall = CGMethodCall(args, nativeName, True,
-                                           self.descriptor, self.constructor)
-        return CGList([CGGeneric(preamble), constructorCall])
+
+            if len(self.exposureSet) == 1:
+                args = [
+                    f"global.downcast::<dom::types::{list(self.exposureSet)[0]}>().unwrap()",
+                    "Some(desired_proto.handle())",
+                    "CanGc::note()"
+                ]
+            else:
+                args = [
+                    "&global",
+                    "Some(desired_proto.handle())",
+                    "CanGc::note()"
+                ]
+
+            constructor = CGMethodCall(args, nativeName, True, self.descriptor, self.constructor)
+            constructorCall = f"""
+            call_default_constructor(
+                cx,
+                &args,
+                global,
+                PrototypeList::ID::{MakeNativeName(self.descriptor.name)},
+                \"{ctorName}\",
+                CreateInterfaceObjects,
+                |cx, args, global, desired_proto| {{
+                    {constructor.define()}
+                }}
+            )
+                """
+        return CGList([CGGeneric(preamble), CGGeneric(constructorCall)])
 
 
 class CGClassFinalizeHook(CGAbstractClassHook):
diff --git a/components/script/dom/bindings/htmlconstructor.rs b/components/script/dom/bindings/constructor.rs
index 56aedc04840..b9c29183b84 100644
--- a/components/script/dom/bindings/htmlconstructor.rs
+++ b/components/script/dom/bindings/constructor.rs
@@ -7,6 +7,7 @@ use std::ptr;
 use html5ever::interface::QualName;
 use html5ever::{local_name, namespace_url, ns, LocalName};
 use js::conversions::ToJSValConvertible;
+use js::gc::RootedGuard;
 use js::glue::{UnwrapObjectDynamic, UnwrapObjectStatic};
 use js::jsapi::{CallArgs, CurrentGlobalOrNull, JSAutoRealm, JSObject};
 use js::rust::wrappers::{JS_SetPrototype, JS_WrapObject};
@@ -40,7 +41,7 @@ use crate::dom::bindings::codegen::Bindings::{
 };
 use crate::dom::bindings::codegen::PrototypeList;
 use crate::dom::bindings::conversions::DerivedFrom;
-use crate::dom::bindings::error::{throw_dom_exception, Error};
+use crate::dom::bindings::error::{throw_constructor_without_new, throw_dom_exception, Error};
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::interface::get_desired_proto;
 use crate::dom::bindings::reflector::DomObject;
@@ -57,14 +58,14 @@ use crate::script_thread::ScriptThread;
 // https://html.spec.whatwg.org/multipage/#htmlconstructor
 unsafe fn html_constructor(
     cx: JSContext,
-    window: &Window,
+    global: &GlobalScope,
     call_args: &CallArgs,
     check_type: fn(&Element) -> bool,
     proto_id: PrototypeList::ID,
     creator: unsafe fn(SafeJSContext, HandleObject, *mut ProtoOrIfaceArray),
 ) -> Result<(), ()> {
+    let window = global.downcast::<Window>().unwrap();
     let document = window.Document();
-    let global = window.upcast::<GlobalScope>();
 
     // Step 1
     let registry = window.CustomElements();
@@ -377,10 +378,10 @@ pub fn push_new_element_queue() {
     ScriptThread::push_new_element_queue();
 }
 
-pub(crate) unsafe fn call_html_constructor<T: DerivedFrom<Element> + DomObject>(
+pub unsafe fn call_html_constructor<T: DerivedFrom<Element> + DomObject>(
     cx: JSContext,
     args: &CallArgs,
-    global: &Window,
+    global: &GlobalScope,
     proto_id: PrototypeList::ID,
     creator: unsafe fn(SafeJSContext, HandleObject, *mut ProtoOrIfaceArray),
 ) -> bool {
@@ -398,3 +399,26 @@ pub(crate) unsafe fn call_html_constructor<T: DerivedFrom<Element> + DomObject>(
     )
     .is_ok()
 }
+
+pub unsafe fn call_default_constructor(
+    cx: JSContext,
+    args: &CallArgs,
+    global: DomRoot<GlobalScope>,
+    proto_id: PrototypeList::ID,
+    ctor_name: &str,
+    creator: unsafe fn(JSContext, HandleObject, *mut ProtoOrIfaceArray),
+    constructor: impl FnOnce(JSContext, &CallArgs, &GlobalScope, RootedGuard<*mut JSObject>) -> bool,
+) -> bool {
+    if !args.is_constructing() {
+        throw_constructor_without_new(*cx, ctor_name);
+        return false;
+    }
+
+    rooted!(in(*cx) let mut desired_proto = ptr::null_mut::<JSObject>());
+    let proto_result = get_desired_proto(cx, args, proto_id, creator, desired_proto.handle_mut());
+    if proto_result.is_err() {
+        return false;
+    }
+
+    constructor(cx, args, &global, desired_proto)
+}
diff --git a/components/script/dom/bindings/import.rs b/components/script/dom/bindings/import.rs
index 32b52cc9845..004696fb92c 100644
--- a/components/script/dom/bindings/import.rs
+++ b/components/script/dom/bindings/import.rs
@@ -103,6 +103,10 @@ pub mod module {
     pub use crate::dom::bindings::codegen::Bindings::EventTargetBinding::EventTarget_Binding;
     pub use crate::dom::bindings::codegen::{InterfaceObjectMap, PrototypeList, RegisterBindings};
     pub use crate::dom::bindings::constant::{ConstantSpec, ConstantVal};
+    pub use crate::dom::bindings::constructor::{
+        call_default_constructor, call_html_constructor, pop_current_element_queue,
+        push_new_element_queue,
+    };
     pub use crate::dom::bindings::conversions::{
         is_array_like, jsid_to_string, native_from_handlevalue, native_from_object_static,
         IDLInterface, StringificationBehavior, ToJSValConvertible, DOM_OBJECT_SLOT,
@@ -112,9 +116,6 @@ pub mod module {
         finalize_common, finalize_global, finalize_weak_referenceable,
     };
     pub use crate::dom::bindings::guard::{Condition, Guard};
-    pub use crate::dom::bindings::htmlconstructor::{
-        pop_current_element_queue, push_new_element_queue,
-    };
     pub use crate::dom::bindings::inheritance::Castable;
     pub use crate::dom::bindings::interface::{
         create_callback_interface_object, create_global_object, create_interface_prototype_object,
diff --git a/components/script/dom/bindings/mod.rs b/components/script/dom/bindings/mod.rs
index 7d6d03d737a..69c327015b3 100644
--- a/components/script/dom/bindings/mod.rs
+++ b/components/script/dom/bindings/mod.rs
@@ -138,11 +138,11 @@ pub mod buffer_source;
 pub mod callback;
 pub mod cell;
 pub mod constant;
+pub mod constructor;
 pub mod conversions;
 pub mod error;
 pub mod finalize;
 pub mod guard;
-pub mod htmlconstructor;
 pub mod import;
 pub mod inheritance;
 pub mod interface;