Add GDExtension support to Script

* Ability to create script languages from GDExtension
* Some additions to gdnative_extension.h to make this happen
* Moved the GDExtension binder to core

This now allows creating scripting languages from GDExtension, with the same ease as if it was a module. It replaces the old PluginScript from Godot 3.x.
Warning: GodotCPP will need to be updated to support this (it may be a bit of work as ScriptInstance needs to be created over there again).

4 files changed, 199 insertions, 0 deletions

diff --git a/core/extension/SCsub b/core/extension/SCsub
index a3a54250c1..23727c1b76 100644
--- a/core/extension/SCsub
+++ b/core/extension/SCsub
@@ -2,6 +2,12 @@
 
 Import("env")
 
+import make_wrappers
+from platform_methods import run_in_subprocess
+
+env.CommandNoCache(["ext_wrappers.gen.inc"], "make_wrappers.py", run_in_subprocess(make_wrappers.run))
+
+
 env_extension = env.Clone()
 
 env_extension.add_source_files(env.core_sources, "*.cpp")
diff --git a/core/extension/gdnative_interface.cpp b/core/extension/gdnative_interface.cpp
index d0461611ec..b5b340731d 100644
--- a/core/extension/gdnative_interface.cpp
+++ b/core/extension/gdnative_interface.cpp
@@ -32,6 +32,7 @@
 
 #include "core/config/engine.h"
 #include "core/object/class_db.h"
+#include "core/object/script_language_extension.h"
 #include "core/os/memory.h"
 #include "core/variant/variant.h"
 #include "core/version.h"
@@ -864,6 +865,13 @@ static GDObjectInstanceID gdnative_object_get_instance_id(const GDNativeObjectPt
 	return (GDObjectInstanceID)o->get_instance_id();
 }
 
+static GDNativeScriptInstancePtr gdnative_script_instance_create(const GDNativeExtensionScriptInstanceInfo *p_info, GDNativeExtensionScriptInstanceDataPtr p_instance_data) {
+	ScriptInstanceExtension *script_instance_extension = memnew(ScriptInstanceExtension);
+	script_instance_extension->instance = p_instance_data;
+	script_instance_extension->native_info = p_info;
+	return reinterpret_cast<GDNativeScriptInstancePtr>(script_instance_extension);
+}
+
 static GDNativeMethodBindPtr gdnative_classdb_get_method_bind(const char *p_classname, const char *p_methodname, GDNativeInt p_hash) {
 	MethodBind *mb = ClassDB::get_method(StringName(p_classname), StringName(p_methodname));
 	ERR_FAIL_COND_V(!mb, nullptr);
@@ -1032,6 +1040,10 @@ void gdnative_setup_interface(GDNativeInterface *p_interface) {
 	gdni.object_get_instance_from_id = gdnative_object_get_instance_from_id;
 	gdni.object_get_instance_id = gdnative_object_get_instance_id;
 
+	/* SCRIPT INSTANCE */
+
+	gdni.script_instance_create = gdnative_script_instance_create;
+
 	/* CLASSDB */
 
 	gdni.classdb_construct_object = gdnative_classdb_construct_object;
diff --git a/core/extension/gdnative_interface.h b/core/extension/gdnative_interface.h
index cc2957ec56..50c747a7b4 100644
--- a/core/extension/gdnative_interface.h
+++ b/core/extension/gdnative_interface.h
@@ -205,6 +205,17 @@ typedef struct {
 	uint32_t usage;
 } GDNativePropertyInfo;
 
+typedef struct {
+	const char *name;
+	GDNativePropertyInfo return_value;
+	uint32_t flags; // From GDNativeExtensionClassMethodFlags
+	int32_t id;
+	GDNativePropertyInfo *arguments;
+	uint32_t argument_count;
+	GDNativeVariantPtr default_arguments;
+	uint32_t default_argument_count;
+} GDNativeMethodInfo;
+
 typedef const GDNativePropertyInfo *(*GDNativeExtensionClassGetPropertyList)(GDExtensionClassInstancePtr p_instance, uint32_t *r_count);
 typedef void (*GDNativeExtensionClassFreePropertyList)(GDExtensionClassInstancePtr p_instance, const GDNativePropertyInfo *p_list);
 typedef void (*GDNativeExtensionClassNotification)(GDExtensionClassInstancePtr p_instance, int32_t p_what);
@@ -289,6 +300,79 @@ typedef struct {
 	GDNativeVariantPtr *default_arguments;
 } GDNativeExtensionClassMethodInfo;
 
+/* SCRIPT INSTANCE EXTENSION */
+
+typedef void *GDNativeExtensionScriptInstanceDataPtr; // Pointer to custom ScriptInstance native implementation
+
+typedef GDNativeBool (*GDNativeExtensionScriptInstanceSet)(GDNativeExtensionScriptInstanceDataPtr p_instance, const GDNativeStringNamePtr p_name, const GDNativeVariantPtr p_value);
+typedef GDNativeBool (*GDNativeExtensionScriptInstanceGet)(GDNativeExtensionScriptInstanceDataPtr p_instance, const GDNativeStringNamePtr p_name, GDNativeVariantPtr r_ret);
+typedef const GDNativePropertyInfo *(*GDNativeExtensionScriptInstanceGetPropertyList)(GDNativeExtensionScriptInstanceDataPtr p_instance, uint32_t *r_count);
+typedef void (*GDNativeExtensionScriptInstanceFreePropertyList)(GDNativeExtensionScriptInstanceDataPtr p_instance, const GDNativePropertyInfo *p_list);
+typedef GDNativeVariantType (*GDNativeExtensionScriptInstanceGetPropertyType)(GDNativeExtensionScriptInstanceDataPtr p_instance, const GDNativeStringNamePtr p_name, GDNativeBool *r_is_valid);
+
+typedef GDNativeObjectPtr (*GDNativeExtensionScriptInstanceGetOwner)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+typedef void (*GDNativeExtensionScriptInstancePropertyStateAdd)(const GDNativeStringNamePtr p_name, const GDNativeVariantPtr p_value, void *p_userdata);
+typedef void (*GDNativeExtensionScriptInstanceGetPropertyState)(GDNativeExtensionScriptInstanceDataPtr p_instance, GDNativeExtensionScriptInstancePropertyStateAdd p_add_func, void *p_userdata);
+
+typedef const GDNativeMethodInfo *(*GDNativeExtensionScriptInstanceGetMethodList)(GDNativeExtensionScriptInstanceDataPtr p_instance, uint32_t *r_count);
+typedef void (*GDNativeExtensionScriptInstanceFreeMethodList)(GDNativeExtensionScriptInstanceDataPtr p_instance, const GDNativeMethodInfo *p_list);
+
+typedef GDNativeBool (*GDNativeExtensionScriptInstanceHasMethod)(GDNativeExtensionScriptInstanceDataPtr p_instance, const GDNativeStringNamePtr p_name);
+
+typedef void (*GDNativeExtensionScriptInstanceCall)(GDNativeExtensionScriptInstanceDataPtr p_self, const GDNativeStringNamePtr p_method, const GDNativeVariantPtr *p_args, const GDNativeInt p_argument_count, GDNativeVariantPtr r_return, GDNativeCallError *r_error);
+typedef void (*GDNativeExtensionScriptInstanceNotification)(GDNativeExtensionScriptInstanceDataPtr p_instance, int32_t p_what);
+typedef const char *(*GDNativeExtensionScriptInstanceToString)(GDNativeExtensionScriptInstanceDataPtr p_instance, GDNativeBool *r_is_valid);
+
+typedef void (*GDNativeExtensionScriptInstanceRefCountIncremented)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+typedef GDNativeBool (*GDNativeExtensionScriptInstanceRefCountDecremented)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+
+typedef GDNativeObjectPtr (*GDNativeExtensionScriptInstanceGetScript)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+typedef GDNativeBool (*GDNativeExtensionScriptInstanceIsPlaceholder)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+
+typedef void *GDNativeExtensionScriptLanguagePtr;
+
+typedef GDNativeExtensionScriptLanguagePtr (*GDNativeExtensionScriptInstanceGetLanguage)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+
+typedef void (*GDNativeExtensionScriptInstanceFree)(GDNativeExtensionScriptInstanceDataPtr p_instance);
+
+typedef void *GDNativeScriptInstancePtr; // Pointer to ScriptInstance.
+
+typedef struct {
+	GDNativeExtensionScriptInstanceSet set_func;
+	GDNativeExtensionScriptInstanceGet get_func;
+	GDNativeExtensionScriptInstanceGetPropertyList get_property_list_func;
+	GDNativeExtensionScriptInstanceFreePropertyList free_property_list_func;
+	GDNativeExtensionScriptInstanceGetPropertyType get_property_type_func;
+
+	GDNativeExtensionScriptInstanceGetOwner get_owner_func;
+	GDNativeExtensionScriptInstanceGetPropertyState get_property_state_func;
+
+	GDNativeExtensionScriptInstanceGetMethodList get_method_list_func;
+	GDNativeExtensionScriptInstanceFreeMethodList free_method_list_func;
+
+	GDNativeExtensionScriptInstanceHasMethod has_method_func;
+
+	GDNativeExtensionScriptInstanceCall call_func;
+	GDNativeExtensionScriptInstanceNotification notification_func;
+
+	GDNativeExtensionScriptInstanceToString to_string_func;
+
+	GDNativeExtensionScriptInstanceRefCountIncremented refcount_incremented_func;
+	GDNativeExtensionScriptInstanceRefCountDecremented refcount_decremented_func;
+
+	GDNativeExtensionScriptInstanceGetScript get_script_func;
+
+	GDNativeExtensionScriptInstanceIsPlaceholder is_placeholder_func;
+
+	GDNativeExtensionScriptInstanceSet set_fallback_func;
+	GDNativeExtensionScriptInstanceGet get_fallback_func;
+
+	GDNativeExtensionScriptInstanceGetLanguage get_language_func;
+
+	GDNativeExtensionScriptInstanceFree free_func;
+
+} GDNativeExtensionScriptInstanceInfo;
+
 /* INTERFACE */
 
 typedef struct {
@@ -441,6 +525,10 @@ typedef struct {
 	GDNativeObjectPtr (*object_get_instance_from_id)(GDObjectInstanceID p_instance_id);
 	GDObjectInstanceID (*object_get_instance_id)(const GDNativeObjectPtr p_object);
 
+	/* SCRIPT INSTANCE */
+
+	GDNativeScriptInstancePtr (*script_instance_create)(const GDNativeExtensionScriptInstanceInfo *p_info, GDNativeExtensionScriptInstanceDataPtr p_instance_data);
+
 	/* CLASSDB */
 	GDNativeObjectPtr (*classdb_construct_object)(const char *p_classname); /* The passed class must be a built-in godot class, or an already-registered extension class. In both case, object_set_instance should be called to fully initialize the object. */
 	GDNativeMethodBindPtr (*classdb_get_method_bind)(const char *p_classname, const char *p_methodname, GDNativeInt p_hash);
diff --git a/core/extension/make_wrappers.py b/core/extension/make_wrappers.py
new file mode 100644
index 0000000000..862d313fba
--- /dev/null
+++ b/core/extension/make_wrappers.py
@@ -0,0 +1,93 @@
+proto = """
+#define EXBIND$VER($RETTYPE m_name$ARG) \\
+GDVIRTUAL$VER($RETTYPE_##m_name$ARG)\\
+virtual $RETVAL m_name($FUNCARGS) $CONST override { \\
+    $RETPRE\\
+    GDVIRTUAL_REQUIRED_CALL(_##m_name$CALLARGS$RETREF);\\
+    $RETPOST\\
+}
+"""
+
+
+def generate_version(argcount, const=False, returns=False):
+    s = proto
+    sproto = str(argcount)
+    method_info = ""
+    if returns:
+        sproto += "R"
+        s = s.replace("$RETTYPE", "m_ret, ")
+        s = s.replace("$RETVAL", "m_ret")
+        s = s.replace("$RETPRE", "m_ret ret; ZeroInitializer<m_ret>::initialize(ret);\\\n")
+        s = s.replace("$RETPOST", "return ret;\\\n")
+
+    else:
+        s = s.replace("$RETTYPE", "")
+        s = s.replace("$RETVAL", "void")
+        s = s.replace("$RETPRE", "")
+        s = s.replace("$RETPOST", "return;")
+
+    if const:
+        sproto += "C"
+        s = s.replace("$CONST", "const")
+    else:
+        s = s.replace("$CONST", "")
+
+    s = s.replace("$VER", sproto)
+    argtext = ""
+    funcargs = ""
+    callargs = ""
+
+    for i in range(argcount):
+        if i > 0:
+            funcargs += ", "
+
+        argtext += ", m_type" + str(i + 1)
+        funcargs += "m_type" + str(i + 1) + " arg" + str(i + 1)
+        callargs += ", arg" + str(i + 1)
+
+    if argcount:
+        s = s.replace("$ARG", argtext)
+        s = s.replace("$FUNCARGS", funcargs)
+        s = s.replace("$CALLARGS", callargs)
+    else:
+        s = s.replace("$ARG", "")
+        s = s.replace("$FUNCARGS", funcargs)
+        s = s.replace("$CALLARGS", callargs)
+
+    if returns:
+        s = s.replace("$RETREF", ", ret")
+    else:
+        s = s.replace("$RETREF", "")
+
+    return s
+
+
+def run(target, source, env):
+
+    max_versions = 12
+
+    txt = """
+#ifndef GDEXTENSION_WRAPPERS_GEN_H
+#define GDEXTENSION_WRAPPERS_GEN_H
+
+
+"""
+
+    for i in range(max_versions + 1):
+
+        txt += "/* " + str(i) + " Arguments */\n\n"
+        txt += generate_version(i, False, False)
+        txt += generate_version(i, False, True)
+        txt += generate_version(i, True, False)
+        txt += generate_version(i, True, True)
+
+    txt += "#endif"
+
+    with open(target[0], "w") as f:
+        f.write(txt)
+
+
+if __name__ == "__main__":
+    from platform_methods import subprocess_main
+
+    subprocess_main(globals())