fix(lua): Make rtorrent.lua accessible at start

src/Makefile.am

@@ -196,4 +196,4 @@ libsub_root_a_SOURCES = \
 	thread_worker.h
 
 
-AM_CPPFLAGS = -I$(srcdir) -I$(top_srcdir)
+AM_CPPFLAGS = -I$(srcdir) -I$(top_srcdir) -DPACKAGE_DATADIR=\"$(pkgdatadir)\"

src/rpc/lua.cc

@@ -25,6 +25,7 @@ namespace rpc {
 
 const int         LuaEngine::flag_string;
 const std::string LuaEngine::module_name = "rtorrent";
+const std::string LuaEngine::local_path = PACKAGE_DATADIR "/lua/?.lua;" PACKAGE_DATADIR "/lua/?/init.lua";
 
 #ifdef HAVE_LUA
 
@@ -32,6 +33,7 @@ LuaEngine::LuaEngine() {
   m_luaState = luaL_newstate();
   luaL_openlibs(m_luaState);
   set_package_preload();
+  override_package_path();
 }
 
 LuaEngine::~LuaEngine() { lua_close(m_luaState); }
@@ -46,6 +48,18 @@ LuaEngine::set_package_preload() {
   lua_pop(l_state, 2);
 }
 
+void
+LuaEngine::override_package_path() {
+  auto l_state = m_luaState;
+  lua_getglobal(l_state, "package");
+  lua_getfield(l_state, -1, "path");
+  std::string current_path(lua_tostring(l_state, -1));
+  std::string new_path = local_path + ';' + current_path;
+  lua_pushstring(l_state, new_path.c_str());
+  lua_setfield(l_state, -3, "path");
+  lua_pop(l_state, 2);
+}
+
 void
 check_lua_status(lua_State* l_state, int status) {
   if (status != LUA_OK) {

src/rpc/lua.h

@@ -14,6 +14,7 @@ class LuaEngine {
 public:
   static const int         flag_string = 0x1;
   static const std::string module_name;
+  static const std::string local_path;
 
   LuaEngine();
   ~LuaEngine();
@@ -23,6 +24,7 @@ public:
   static int lua_init_module(lua_State* l_state);
   static int lua_rtorrent_call(lua_State* l_state);
   void       set_package_preload();
+  void       override_package_path();
   lua_State* state() { return m_luaState; }
 
 private: