feat(plugins): add debug.traceback (#6652)

Reviewed-by: Mm2PL <mm2pl+gh@kotmisia.pl>

src/controllers/plugins/PluginController.cpp

@@ -9,6 +9,7 @@
 #    include "controllers/commands/CommandController.hpp"
 #    include "controllers/plugins/api/Accounts.hpp"
 #    include "controllers/plugins/api/ChannelRef.hpp"
+#    include "controllers/plugins/api/DebugLibrary.hpp"
 #    include "controllers/plugins/api/HTTPRequest.hpp"
 #    include "controllers/plugins/api/HTTPResponse.hpp"
 #    include "controllers/plugins/api/IOWrapper.hpp"
@@ -207,6 +208,13 @@ void PluginController::openLibrariesFor(Plugin *plugin)
         r["_IO_input"] = sol::nil;
         r["_IO_output"] = sol::nil;
     }
+    // set up debug lib
+    {
+        auto debuglib = lua.create_table();
+        g["debug"] = debuglib;
+
+        debuglib.set_function("traceback", lua::api::debugTraceback);
+    }
     PluginController::initSol(lua, plugin);
 }
 

src/controllers/plugins/api/DebugLibrary.cpp

@@ -0,0 +1,46 @@
+#include "controllers/plugins/api/DebugLibrary.hpp"
+
+#ifdef CHATTERINO_HAVE_PLUGINS
+
+#    include <sol/sol.hpp>
+
+namespace chatterino::lua::api {
+
+/// Signature in Lua: ([thread,] [message [, level]])
+int debugTraceback(lua_State *L)
+{
+    int argOffset = 1;
+    lua_State *targetThread = L;
+
+    // If the first argument is a thread, take that as our target
+    if (lua_isthread(L, argOffset))
+    {
+        targetThread = lua_tothread(L, argOffset);
+        argOffset += 1;
+    }
+
+    // The message is an optional string. If it's not a string/number/nil, we
+    // return the message as-is and don't create a traceback.
+    const char *msg = lua_tostring(L, argOffset);
+    if (!msg && !lua_isnoneornil(L, argOffset))
+    {
+        lua_pushvalue(L, argOffset);
+        return 1;
+    }
+    argOffset += 1;
+
+    int defaultLevel = 0;
+    if (L == targetThread)
+    {
+        defaultLevel = 1;
+    }
+
+    int level = static_cast<int>(luaL_optinteger(L, argOffset, defaultLevel));
+    // push a traceback with `msg` at the start
+    luaL_traceback(L, targetThread, msg, level);
+    return 1;
+}
+
+}  // namespace chatterino::lua::api
+
+#endif

src/controllers/plugins/api/DebugLibrary.hpp

@@ -0,0 +1,14 @@
+#pragma once
+#ifdef CHATTERINO_HAVE_PLUGINS
+#    include <sol/forward.hpp>
+
+namespace chatterino::lua::api {
+
+/// A reimplementation of Lua's debug.traceback (ldblib.c).
+/// Creates a traceback of a thread.
+/// It's intended to be used as a message handler in `xpcall`.
+/// See https://www.lua.org/manual/5.4/manual.html#pdf-debug.traceback
+int debugTraceback(lua_State *L);
+
+}  // namespace chatterino::lua::api
+#endif