Use a Lua error handler that calls tostring (#11913)

2 files changed, 26 insertions, 4 deletions

diff --git a/src/script/common/c_internal.cpp b/src/script/common/c_internal.cpp
index ddd2d184c..79063141d 100644
--- a/src/script/common/c_internal.cpp
+++ b/src/script/common/c_internal.cpp
@@ -27,10 +27,11 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 std::string script_get_backtrace(lua_State *L)
 {
-	lua_rawgeti(L, LUA_REGISTRYINDEX, CUSTOM_RIDX_BACKTRACE);
+	lua_getglobal(L, "debug");
+	lua_getfield(L, -1, "traceback");
 	lua_call(L, 0, 1);
 	std::string result = luaL_checkstring(L, -1);
-	lua_pop(L, 1);
+	lua_pop(L, 2);
 	return result;
 }
 
@@ -46,6 +47,25 @@ int script_exception_wrapper(lua_State *L, lua_CFunction f)
 	return lua_error(L);  // Rethrow as a Lua error.
 }
 
+int script_error_handler(lua_State *L)
+{
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "error_handler");
+	if (!lua_isnil(L, -1)) {
+		lua_pushvalue(L, 1);
+	} else {
+		// No Lua error handler available. Call debug.traceback(tostring(#1), level).
+		lua_getglobal(L, "debug");
+		lua_getfield(L, -1, "traceback");
+		lua_getglobal(L, "tostring");
+		lua_pushvalue(L, 1);
+		lua_call(L, 1, 1);
+	}
+	lua_pushinteger(L, 2); // Stack level
+	lua_call(L, 2, 1);
+	return 1;
+}
+
 /*
  * Note that we can't get tracebacks for LUA_ERRMEM or LUA_ERRERR (without
  * hacking Lua internals).  For LUA_ERRMEM, this is because memory errors will
diff --git a/src/script/common/c_internal.h b/src/script/common/c_internal.h
index 5cbcbb7db..c8bce099c 100644
--- a/src/script/common/c_internal.h
+++ b/src/script/common/c_internal.h
@@ -54,7 +54,7 @@ enum {
 	CUSTOM_RIDX_SCRIPTAPI,
 	CUSTOM_RIDX_GLOBALS_BACKUP,
 	CUSTOM_RIDX_CURRENT_MOD_NAME,
-	CUSTOM_RIDX_BACKTRACE,
+	CUSTOM_RIDX_ERROR_HANDLER,
 	CUSTOM_RIDX_HTTP_API_LUA,
 	CUSTOM_RIDX_METATABLE_MAP,
 
@@ -78,7 +78,7 @@ enum {
 
 // Pushes the error handler onto the stack and returns its index
 #define PUSH_ERROR_HANDLER(L) \
-	(lua_rawgeti((L), LUA_REGISTRYINDEX, CUSTOM_RIDX_BACKTRACE), lua_gettop((L)))
+	(lua_rawgeti((L), LUA_REGISTRYINDEX, CUSTOM_RIDX_ERROR_HANDLER), lua_gettop((L)))
 
 #define PCALL_RESL(L, RES) {                            \
 	int result_ = (RES);                                \
@@ -121,6 +121,8 @@ enum RunCallbacksMode
 std::string script_get_backtrace(lua_State *L);
 // Wrapper for CFunction calls that converts C++ exceptions to Lua errors
 int script_exception_wrapper(lua_State *L, lua_CFunction f);
+// Acts as the error handler for lua_pcall
+int script_error_handler(lua_State *L);
 // Takes an error from lua_pcall and throws it as a LuaError
 void script_error(lua_State *L, int pcall_result, const char *mod, const char *fxn);