Detect whether virtual functions are required to override

From Godot 4.4 onward, we can use the GDExtension-provided information, which states whether
virtual functions have a default implementation or are required to be overridden.

godot-codegen/src/models/domain_mapping.rs

@@ -456,6 +456,22 @@ impl ClassMethod {
             FnQualifier::from_const_static(is_actually_const, method.is_static)
         };
 
+        // Since Godot 4.4, GDExtension advertises whether virtual methods have a default implementation or are required to be overridden.
+        #[cfg(before_api = "4.4")]
+        let is_virtual_required = special_cases::is_virtual_method_required(
+            &class_name.rust_ty.to_string(),
+            rust_method_name,
+        );
+
+        #[cfg(since_api = "4.4")]
+        let is_virtual_required = method.is_virtual
+            && method.is_required.unwrap_or_else(|| {
+                panic!(
+                    "virtual method {}::{} lacks field `is_required`",
+                    class_name.rust_ty, rust_method_name
+                );
+            });
+
         Some(Self {
             common: FunctionCommon {
                 name: rust_method_name.to_string(),
@@ -464,10 +480,7 @@ impl ClassMethod {
                 return_value: FnReturn::new(&method.return_value, ctx),
                 is_vararg: method.is_vararg,
                 is_private,
-                is_virtual_required: special_cases::is_virtual_method_required(
-                    &class_name.rust_ty.to_string(),
-                    rust_method_name,
-                ),
+                is_virtual_required,
                 direction,
             },
             qualifier,

godot-codegen/src/models/json.rs

@@ -220,6 +220,8 @@ pub struct JsonClassMethod {
     pub is_vararg: bool,
     pub is_static: bool,
     pub is_virtual: bool,
+    #[cfg(since_api = "4.4")]
+    pub is_required: Option<bool>, // Only virtual functions have this field.
     pub hash: Option<i64>,
     pub return_value: Option<JsonMethodReturn>,
     pub arguments: Option<Vec<JsonMethodArg>>,

godot-codegen/src/special_cases/special_cases.rs

@@ -389,6 +389,7 @@ pub fn get_interface_extra_docs(trait_name: &str) -> Option<&'static str> {
     }
 }
 
+#[cfg(before_api = "4.4")]
 pub fn is_virtual_method_required(class_name: &str, method: &str) -> bool {
     match (class_name, method) {
         ("ScriptLanguageExtension", _) => method != "get_doc_comment_delimiters",