Add GDNative JSON generator for the builtin API

Which can be used by language bindings to generate code statically. This
is generated as a different file from the class API because it has
different requirements (the builtin types have constructors and don't
have signals), so bindings can better make use of each JSON file without
extra parsing.

This also cleans up a bit the old API generator, mainly initializing
structs and renaming "instanciable" to the more correct "instantiable".

The argument description in help text was updated to better reflect how
it should be used. The <path> argument is mandatory.

3 files changed, 404 insertions, 18 deletions

diff --git a/modules/gdnative/nativescript/api_generator.cpp b/modules/gdnative/nativescript/api_generator.cpp
index 6b46c9418a..2b824938f2 100644
--- a/modules/gdnative/nativescript/api_generator.cpp
+++ b/modules/gdnative/nativescript/api_generator.cpp
@@ -36,6 +36,7 @@
 #include "core/core_constants.h"
 #include "core/object/class_db.h"
 #include "core/os/file_access.h"
+#include "core/string/string_builder.h"
 #include "core/templates/pair.h"
 
 // helper stuff
@@ -65,14 +66,14 @@ struct MethodAPI {
 
 	Map<int, Variant> default_arguments;
 
-	int argument_count;
-	bool has_varargs;
-	bool is_editor;
-	bool is_noscript;
-	bool is_const;
-	bool is_reverse;
-	bool is_virtual;
-	bool is_from_script;
+	int argument_count = 0;
+	bool has_varargs = false;
+	bool is_editor = false;
+	bool is_noscript = false;
+	bool is_const = false;
+	bool is_reverse = false;
+	bool is_virtual = false;
+	bool is_from_script = false;
 };
 
 struct PropertyAPI {
@@ -80,12 +81,14 @@ struct PropertyAPI {
 	String getter;
 	String setter;
 	String type;
-	int index;
+	int index = 0;
 };
 
 struct ConstantAPI {
 	String constant_name;
-	int constant_value;
+	int constant_value = 0;
+	Variant builtin_constant_value; // For builtin types;
+	String builtin_constant_type; // For builtin types;
 };
 
 struct SignalAPI {
@@ -100,23 +103,34 @@ struct EnumAPI {
 	List<Pair<int, String>> values;
 };
 
+struct OperatorAPI { // For builtin types;
+	String name;
+	int oper = Variant::OP_MAX;
+	String other_type;
+	String return_type;
+};
+
 struct ClassAPI {
 	String class_name;
 	String super_class_name;
 
-	ClassDB::APIType api_type;
+	ClassDB::APIType api_type = ClassDB::API_NONE;
 
-	bool is_singleton;
+	bool is_singleton = false;
 	String singleton_name;
-	bool is_instanciable;
+	bool is_instantiable = false;
 	// @Unclear
-	bool is_reference;
+	bool is_reference = false;
+	bool has_indexing = false; // For builtin types.
+	bool is_keyed = false; // For builtin types.
 
 	List<MethodAPI> methods;
+	List<MethodAPI> constructors; // For builtin types.
 	List<PropertyAPI> properties;
 	List<ConstantAPI> constants;
 	List<SignalAPI> signals_;
 	List<EnumAPI> enums;
+	List<OperatorAPI> operators; // For builtin types.
 };
 
 static String get_type_name(const PropertyInfo &info) {
@@ -180,7 +194,7 @@ List<ClassAPI> generate_c_api_classes() {
 		global_constants_api.api_type = ClassDB::API_CORE;
 		global_constants_api.is_singleton = true;
 		global_constants_api.singleton_name = "CoreConstants";
-		global_constants_api.is_instanciable = false;
+		global_constants_api.is_instantiable = false;
 		const int constants_count = CoreConstants::get_global_constant_count();
 		for (int i = 0; i < constants_count; ++i) {
 			ConstantAPI constant_api;
@@ -195,6 +209,10 @@ List<ClassAPI> generate_c_api_classes() {
 	for (List<StringName>::Element *e = classes.front(); e != nullptr; e = e->next()) {
 		StringName class_name = e->get();
 
+		if (!ClassDB::is_class_exposed(class_name)) {
+			continue;
+		}
+
 		ClassAPI class_api;
 		class_api.api_type = ClassDB::get_api_type(e->get());
 		class_api.class_name = class_name;
@@ -209,7 +227,7 @@ List<ClassAPI> generate_c_api_classes() {
 				class_api.singleton_name = name;
 			}
 		}
-		class_api.is_instanciable = !class_api.is_singleton && ClassDB::can_instance(class_name);
+		class_api.is_instantiable = !class_api.is_singleton && ClassDB::can_instance(class_name);
 
 		{
 			List<StringName> inheriters;
@@ -402,6 +420,191 @@ List<ClassAPI> generate_c_api_classes() {
 }
 
 /*
+ * Reads the builtin Variant API to a list
+ */
+List<ClassAPI> generate_c_builtin_api_types() {
+	List<ClassAPI> api;
+
+	// Special class for the utility methods.
+	{
+		ClassAPI utility_api;
+		utility_api.class_name = "Utilities";
+		utility_api.is_instantiable = false;
+
+		List<StringName> utility_functions;
+		Variant::get_utility_function_list(&utility_functions);
+		for (const List<StringName>::Element *E = utility_functions.front(); E; E = E->next()) {
+			const StringName &function_name = E->get();
+
+			MethodAPI function_api;
+			function_api.method_name = function_name;
+			function_api.has_varargs = Variant::is_utility_function_vararg(function_name);
+			function_api.argument_count = function_api.has_varargs ? 0 : Variant::get_utility_function_argument_count(function_name);
+			function_api.is_const = Variant::get_utility_function_type(function_name) == Variant::UTILITY_FUNC_TYPE_MATH;
+
+			for (int i = 0; i < function_api.argument_count; i++) {
+				function_api.argument_names.push_back(Variant::get_utility_function_argument_name(function_name, i));
+				Variant::Type arg_type = Variant::get_utility_function_argument_type(function_name, i);
+				function_api.argument_types.push_back(arg_type == Variant::NIL ? "Variant" : Variant::get_type_name(arg_type));
+			}
+
+			if (Variant::has_utility_function_return_value(function_name)) {
+				Variant::Type ret_type = Variant::get_utility_function_return_type(function_name);
+				function_api.return_type = ret_type == Variant::NIL ? "Variant" : Variant::get_type_name(ret_type);
+			} else {
+				function_api.return_type = "void";
+			}
+
+			utility_api.methods.push_back(function_api);
+		}
+
+		api.push_back(utility_api);
+	}
+
+	for (int t = 0; t < Variant::VARIANT_MAX; t++) {
+		Variant::Type type = (Variant::Type)t;
+
+		ClassAPI class_api;
+		class_api.class_name = Variant::get_type_name(type);
+		class_api.is_instantiable = true;
+		class_api.has_indexing = Variant::has_indexing(type);
+		class_api.is_keyed = Variant::is_keyed(type);
+		// Types that are passed by reference.
+		switch (type) {
+			case Variant::OBJECT:
+			case Variant::DICTIONARY:
+			case Variant::ARRAY:
+			case Variant::PACKED_BYTE_ARRAY:
+			case Variant::PACKED_INT32_ARRAY:
+			case Variant::PACKED_INT64_ARRAY:
+			case Variant::PACKED_FLOAT32_ARRAY:
+			case Variant::PACKED_FLOAT64_ARRAY:
+			case Variant::PACKED_STRING_ARRAY:
+			case Variant::PACKED_VECTOR2_ARRAY:
+			case Variant::PACKED_VECTOR3_ARRAY:
+			case Variant::PACKED_COLOR_ARRAY:
+				class_api.is_reference = true;
+				break;
+			default:
+				class_api.is_reference = false;
+				break;
+		}
+
+		// Methods.
+
+		List<StringName> methods;
+		Variant::get_builtin_method_list(type, &methods);
+		for (const List<StringName>::Element *E = methods.front(); E; E = E->next()) {
+			const StringName &method_name = E->get();
+
+			MethodAPI method_api;
+
+			method_api.method_name = method_name;
+			method_api.argument_count = Variant::get_builtin_method_argument_count(type, method_name);
+			method_api.has_varargs = Variant::is_builtin_method_vararg(type, method_name);
+			method_api.is_const = Variant::is_builtin_method_const(type, method_name);
+
+			for (int i = 0; i < method_api.argument_count; i++) {
+				method_api.argument_names.push_back(Variant::get_builtin_method_argument_name(type, method_name, i));
+				Variant::Type arg_type = Variant::get_builtin_method_argument_type(type, method_name, i);
+				method_api.argument_types.push_back(arg_type == Variant::NIL ? "Variant" : Variant::get_type_name(arg_type));
+			}
+
+			Vector<Variant> default_arguments = Variant::get_builtin_method_default_arguments(type, method_name);
+
+			int default_start = method_api.argument_names.size() - default_arguments.size();
+
+			for (int i = 0; i < default_arguments.size(); i++) {
+				method_api.default_arguments[default_start + i] = default_arguments[i];
+			}
+
+			if (Variant::has_builtin_method_return_value(type, method_name)) {
+				Variant::Type ret_type = Variant::get_builtin_method_return_type(type, method_name);
+				method_api.return_type = ret_type == Variant::NIL ? "Variant" : Variant::get_type_name(ret_type);
+			} else {
+				method_api.return_type = "void";
+			}
+
+			class_api.methods.push_back(method_api);
+		}
+
+		// Constructors.
+
+		for (int c = 0; c < Variant::get_constructor_count(type); c++) {
+			MethodAPI constructor_api;
+
+			constructor_api.method_name = Variant::get_type_name(type);
+			constructor_api.argument_count = Variant::get_constructor_argument_count(type, c);
+			constructor_api.return_type = Variant::get_type_name(type);
+
+			for (int i = 0; i < constructor_api.argument_count; i++) {
+				constructor_api.argument_names.push_back(Variant::get_constructor_argument_name(type, c, i));
+				Variant::Type arg_type = Variant::get_constructor_argument_type(type, c, i);
+				constructor_api.argument_types.push_back(arg_type == Variant::NIL ? "Variant" : Variant::get_type_name(arg_type));
+			}
+
+			class_api.constructors.push_back(constructor_api);
+		}
+
+		// Constants.
+
+		List<StringName> constants;
+		Variant::get_constants_for_type(type, &constants);
+		for (const List<StringName>::Element *E = constants.front(); E; E = E->next()) {
+			const StringName &constant_name = E->get();
+			ConstantAPI constant_api;
+
+			constant_api.constant_name = constant_name;
+			constant_api.builtin_constant_value = Variant::get_constant_value(type, constant_name);
+			constant_api.builtin_constant_type = Variant::get_type_name(constant_api.builtin_constant_value.get_type());
+
+			class_api.constants.push_back(constant_api);
+		}
+
+		// Members.
+
+		List<StringName> members;
+		Variant::get_member_list(type, &members);
+		for (const List<StringName>::Element *E = members.front(); E; E = E->next()) {
+			const StringName &member_name = E->get();
+
+			PropertyAPI member_api;
+			member_api.name = member_name;
+			Variant::Type member_type = Variant::get_member_type(type, member_name);
+			member_api.type = member_type == Variant::NIL ? "Variant" : Variant::get_type_name(member_type);
+
+			class_api.properties.push_back(member_api);
+		}
+
+		// Operators.
+
+		for (int op = 0; op < Variant::OP_MAX; op++) {
+			Variant::Operator oper = (Variant::Operator)op;
+
+			for (int ot = 0; ot < Variant::VARIANT_MAX; ot++) {
+				Variant::Type other_type = (Variant::Type)ot;
+
+				if (!Variant::get_validated_operator_evaluator(oper, type, other_type)) {
+					continue;
+				}
+
+				OperatorAPI oper_api;
+				oper_api.name = Variant::get_operator_name(oper);
+				oper_api.oper = oper;
+				oper_api.other_type = Variant::get_type_name(other_type);
+				oper_api.return_type = Variant::get_type_name(Variant::get_operator_return_type(oper, type, other_type));
+
+				class_api.operators.push_back(oper_api);
+			}
+		}
+
+		api.push_back(class_api);
+	}
+
+	return api;
+}
+
+/*
  * Generates the JSON source from the API in p_api
  */
 static List<String> generate_c_api_json(const List<ClassAPI> &p_api) {
@@ -421,9 +624,8 @@ static List<String> generate_c_api_json(const List<ClassAPI> &p_api) {
 		source.push_back(String("\t\t\"api_type\": \"") + (api.api_type == ClassDB::API_CORE ? "core" : (api.api_type == ClassDB::API_EDITOR ? "tools" : "none")) + "\",\n");
 		source.push_back(String("\t\t\"singleton\": ") + (api.is_singleton ? "true" : "false") + ",\n");
 		source.push_back("\t\t\"singleton_name\": \"" + api.singleton_name + "\",\n");
-		source.push_back(String("\t\t\"instanciable\": ") + (api.is_instanciable ? "true" : "false") + ",\n");
+		source.push_back(String("\t\t\"instantiable\": ") + (api.is_instantiable ? "true" : "false") + ",\n");
 		source.push_back(String("\t\t\"is_reference\": ") + (api.is_reference ? "true" : "false") + ",\n");
-		// @Unclear
 
 		source.push_back("\t\t\"constants\": {\n");
 		for (List<ConstantAPI>::Element *e = api.constants.front(); e; e = e->next()) {
@@ -508,6 +710,164 @@ static List<String> generate_c_api_json(const List<ClassAPI> &p_api) {
 	return source;
 }
 
+static int indent_level = 0;
+
+static void append_indented(StringBuilder &p_source, const String &p_text) {
+	for (int i = 0; i < indent_level; i++) {
+		p_source.append("\t");
+	}
+	p_source.append(p_text);
+	p_source.append("\n");
+}
+
+static void append_indented(StringBuilder &p_source, const char *p_text) {
+	for (int i = 0; i < indent_level; i++) {
+		p_source.append("\t");
+	}
+	p_source.append(p_text);
+	p_source.append("\n");
+}
+
+static void write_builtin_method(StringBuilder &p_source, const MethodAPI &p_method) {
+	append_indented(p_source, vformat(R"("name": "%s",)", p_method.method_name));
+	append_indented(p_source, vformat(R"("return_type": "%s",)", p_method.return_type));
+	append_indented(p_source, vformat(R"("is_const": %s,)", p_method.is_const ? "true" : "false"));
+	append_indented(p_source, vformat(R"("has_varargs": %s,)", p_method.has_varargs ? "true" : "false"));
+
+	append_indented(p_source, R"("arguments": [)");
+	indent_level++;
+	for (int i = 0; i < p_method.argument_count; i++) {
+		append_indented(p_source, "{");
+		indent_level++;
+
+		append_indented(p_source, vformat(R"("name": "%s",)", p_method.argument_names[i]));
+		append_indented(p_source, vformat(R"("type": "%s",)", p_method.argument_types[i]));
+		append_indented(p_source, vformat(R"("has_default_value": %s,)", p_method.default_arguments.has(i) ? "true" : "false"));
+		append_indented(p_source, vformat(R"("default_value": "%s")", p_method.default_arguments.has(i) ? p_method.default_arguments[i].operator String() : ""));
+
+		indent_level--;
+		append_indented(p_source, i < p_method.argument_count - 1 ? "}," : "}");
+	}
+	indent_level--;
+	append_indented(p_source, "]");
+}
+
+static List<String> generate_c_builtin_api_json(const List<ClassAPI> &p_api) {
+	StringBuilder source;
+
+	source.append("[\n");
+
+	indent_level = 1;
+
+	for (const List<ClassAPI>::Element *C = p_api.front(); C; C = C->next()) {
+		const ClassAPI &class_api = C->get();
+		append_indented(source, "{");
+		indent_level++;
+
+		append_indented(source, vformat(R"("name": "%s",)", class_api.class_name));
+		append_indented(source, vformat(R"("is_instantiable": %s,)", class_api.is_instantiable ? "true" : "false"));
+		append_indented(source, vformat(R"("is_reference": %s,)", class_api.is_reference ? "true" : "false"));
+		append_indented(source, vformat(R"("has_indexing": %s,)", class_api.has_indexing ? "true" : "false"));
+		append_indented(source, vformat(R"("is_keyed": %s,)", class_api.is_keyed ? "true" : "false"));
+
+		// Constructors.
+		append_indented(source, R"("constructors": [)");
+		indent_level++;
+		for (const List<MethodAPI>::Element *E = class_api.constructors.front(); E; E = E->next()) {
+			const MethodAPI &constructor = E->get();
+			append_indented(source, "{");
+			indent_level++;
+
+			write_builtin_method(source, constructor);
+
+			indent_level--;
+			append_indented(source, E->next() ? "}," : "}");
+		}
+		indent_level--;
+		append_indented(source, "],");
+
+		// Constants.
+		append_indented(source, R"("constants": [)");
+		indent_level++;
+		for (const List<ConstantAPI>::Element *E = class_api.constants.front(); E; E = E->next()) {
+			const ConstantAPI &constant = E->get();
+			append_indented(source, "{");
+			indent_level++;
+
+			append_indented(source, vformat(R"("name": "%s",)", constant.constant_name));
+			append_indented(source, vformat(R"("type": "%s",)", constant.builtin_constant_type));
+			append_indented(source, vformat(R"("value": "%s")", constant.builtin_constant_value.operator String()));
+
+			indent_level--;
+			append_indented(source, E->next() ? "}," : "}");
+		}
+		indent_level--;
+		append_indented(source, "],");
+
+		// Methods.
+		append_indented(source, R"("methods": [)");
+		indent_level++;
+		for (const List<MethodAPI>::Element *E = class_api.methods.front(); E; E = E->next()) {
+			const MethodAPI &method = E->get();
+			append_indented(source, "{");
+			indent_level++;
+
+			write_builtin_method(source, method);
+
+			indent_level--;
+			append_indented(source, E->next() ? "}," : "}");
+		}
+		indent_level--;
+		append_indented(source, "],");
+
+		// Members.
+		append_indented(source, R"("members": [)");
+		indent_level++;
+		for (const List<PropertyAPI>::Element *E = class_api.properties.front(); E; E = E->next()) {
+			const PropertyAPI &member = E->get();
+			append_indented(source, "{");
+			indent_level++;
+
+			append_indented(source, vformat(R"("name": "%s",)", member.name));
+			append_indented(source, vformat(R"("type": "%s")", member.type));
+
+			indent_level--;
+			append_indented(source, E->next() ? "}," : "}");
+		}
+		indent_level--;
+		append_indented(source, "],");
+
+		// Operators.
+		append_indented(source, R"("operators": [)");
+		indent_level++;
+		for (const List<OperatorAPI>::Element *E = class_api.operators.front(); E; E = E->next()) {
+			const OperatorAPI &oper = E->get();
+			append_indented(source, "{");
+			indent_level++;
+
+			append_indented(source, vformat(R"("name": "%s",)", oper.name));
+			append_indented(source, vformat(R"("operator": %d,)", oper.oper));
+			append_indented(source, vformat(R"("other_type": "%s",)", oper.other_type));
+			append_indented(source, vformat(R"("return_type": "%s")", oper.return_type));
+
+			indent_level--;
+			append_indented(source, E->next() ? "}," : "}");
+		}
+		indent_level--;
+		append_indented(source, "]");
+
+		indent_level--;
+		append_indented(source, C->next() ? "}," : "}");
+	}
+
+	indent_level--;
+	source.append("]\n");
+
+	List<String> result;
+	result.push_back(source.as_string());
+	return result;
+}
+
 #endif
 
 /*
@@ -526,3 +886,19 @@ Error generate_c_api(const String &p_path) {
 	return save_file(p_path, json_source);
 #endif
 }
+/*
+ * Saves the builtin Godot API to a JSON file located at
+ *  p_path
+ */
+Error generate_c_builtin_api(const String &p_path) {
+#ifndef TOOLS_ENABLED
+	return ERR_BUG;
+#else
+
+	List<ClassAPI> api = generate_c_builtin_api_types();
+
+	List<String> json_source = generate_c_builtin_api_json(api);
+
+	return save_file(p_path, json_source);
+#endif
+}
diff --git a/modules/gdnative/nativescript/api_generator.h b/modules/gdnative/nativescript/api_generator.h
index a324ded4a9..611abb2a2d 100644
--- a/modules/gdnative/nativescript/api_generator.h
+++ b/modules/gdnative/nativescript/api_generator.h
@@ -35,5 +35,6 @@
 #include "core/typedefs.h"
 
 Error generate_c_api(const String &p_path);
+Error generate_c_builtin_api(const String &p_path);
 
 #endif // API_GENERATOR_H
diff --git a/modules/gdnative/nativescript/nativescript.cpp b/modules/gdnative/nativescript/nativescript.cpp
index 944f4f052c..19cf1f980b 100644
--- a/modules/gdnative/nativescript/nativescript.cpp
+++ b/modules/gdnative/nativescript/nativescript.cpp
@@ -1257,6 +1257,15 @@ void NativeScriptLanguage::init() {
 		}
 		exit(0);
 	}
+
+	E = args.find("--gdnative-generate-json-builtin-api");
+
+	if (E && E->next()) {
+		if (generate_c_builtin_api(E->next()->get()) != OK) {
+			ERR_PRINT("Failed to generate C builtin API\n");
+		}
+		exit(0);
+	}
 #endif
 
 #ifdef TOOLS_ENABLED