From f749b7fb18d4662c86bfb23a82cb4d31a23ff7c7 Mon Sep 17 00:00:00 2001
From: King_DuckZ <king_duckz@gmx.com>
Date: Fri, 22 Apr 2022 22:04:09 +0200
Subject: [PATCH] call() will fail earlier when object for call doesn't exist

---
 include/wrenpp/vm.hpp |  7 +++++--
 src/vm.cpp            | 24 ++++++++++++++++++++++--
 src/vm_fun.cpp        |  2 +-
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/include/wrenpp/vm.hpp b/include/wrenpp/vm.hpp
index ea0b742..88a3208 100644
--- a/include/wrenpp/vm.hpp
+++ b/include/wrenpp/vm.hpp
@@ -79,7 +79,8 @@ namespace wren {
 		void release_handle (Handle& handle) noexcept;
 		void ensure_slots(int num_slots);
 		int slot_count();
-		void variable(const char* module, const char* name, int slot);
+		void variable(const char* module, const char* name, int slot) noexcept;
+		void variable_or_throw(const char* module, const char* name, int slot);
 		void set_slot_handle(const Handle& handle, int slot);
 		SlotType slot_type(int slot_num);
 		Handle slot_handle(int slot_num);
@@ -103,7 +104,9 @@ namespace wren {
 		template <typename U> U* user_data();
 		template <typename U> void set_user_data (U* user_data);
 		void set_user_data (std::nullptr_t);
-		bool has_user_data() const;
+		bool has_user_data() const noexcept;
+		bool has_module (const char* module) const noexcept;
+		bool has_variable (const char* module, const char* name) const noexcept;
 
 		std::size_t dynafunc_byte_size() const;
 		void reset (Configuration* conf);
diff --git a/src/vm.cpp b/src/vm.cpp
index 7985ff0..977f960 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -266,10 +266,18 @@ namespace wren {
 		m_local->user_data_type = detail::type_id<std::nullptr_t>();
 	}
 
-	bool VM::has_user_data() const {
+	bool VM::has_user_data() const noexcept {
 		return nullptr != m_local->user_data;
 	}
 
+	bool VM::has_module(const char* module) const noexcept {
+		return wrenHasModule(m_local->wvm, module);
+	}
+
+	bool VM::has_variable(const char* module, const char* name) const noexcept {
+		return wrenHasVariable(m_local->wvm, module, name);
+	}
+
 	std::size_t VM::dynafunc_byte_size() const {
 		return m_local->dynafunc.total_memory();
 	}
@@ -322,11 +330,23 @@ namespace wren {
 		return wrenGetSlotCount(m_local->wvm);
 	}
 
-	void VM::variable(const char* module, const char* name, int slot) {
+	void VM::variable(const char* module, const char* name, int slot) noexcept {
 		assert(slot_count() >= 1);
 		wrenGetVariable(m_local->wvm, module, name, slot);
 	}
 
+	void VM::variable_or_throw(const char* module, const char* name, int slot) {
+		using std::string;
+		using std::runtime_error;
+
+		if (not has_module(module))
+			throw runtime_error(string{"Module "} + module + " is unknown");
+		if (not has_variable(module, name))
+			throw runtime_error(string{"Variable "} + module + "::" + name + " not found");
+
+		variable(module, name, slot);
+	}
+
 	void VM::set_slot_handle (const Handle& handle, int slot) {
 		wrenSetSlotHandle(m_local->wvm, slot, handle);
 	}
diff --git a/src/vm_fun.cpp b/src/vm_fun.cpp
index 57fb118..3a9797b 100644
--- a/src/vm_fun.cpp
+++ b/src/vm_fun.cpp
@@ -73,7 +73,7 @@ namespace wren {
 	}
 
 	void variable(VM& vm, const ModuleAndName& mod_and_name, int slot) {
-		vm.variable(std::get<0>(mod_and_name), std::get<1>(mod_and_name), slot);
+		vm.variable_or_throw(std::get<0>(mod_and_name), std::get<1>(mod_and_name), slot);
 	}
 
 	void variable (VM& vm, const Handle& handle, int slot) {