fix entities.spawn in coroutines

dev/tests/base_entities.lua

@@ -1,10 +1,12 @@
-local util = require("core:tests_util")
+local util = require "core:tests_util"
 
 -- Create world and prepare settings
 util.create_demo_world("core:default")
 app.set_setting("chunks.load-distance", 3)
 app.set_setting("chunks.load-speed", 1)
 
+local base_util = require "base:util"
+
 -- Create player
 local pid = player.create("Xerxes")
 player.set_spawnpoint(pid, 0, 100, 0)
@@ -22,3 +24,7 @@ assert(block.get(0, 2, 0) == 0)
 
 -- Wait for the block to fall
 app.sleep_until(function () return block.get(0, 1, 0) == block.index("base:sand") end, 100)
+
+local drop = base_util.drop({player.get_pos(pid)}, item.index("base:bazalt_breaker"), 11)
+assert(drop ~= nil)
+assert(drop.rigidbody ~= nil)

src/logic/scripting/lua/libs/libentity.cpp

@@ -63,8 +63,10 @@ static int l_spawn(lua::State* L) {
     if (lua::gettop(L) > 2) {
         args = lua::tovalue(L, 3);
     }
-    level->entities->spawn(def, pos, std::move(args));
-    return 1;
+    entityid_t id = level->entities->spawn(def, pos, std::move(args));
+    lua::get_from(L, "entities", "get", true);
+    lua::pushinteger(L, id);
+    return lua::call_nothrow(L, 1);
 }
 
 static int l_despawn(lua::State* L) {

src/logic/scripting/scripting.cpp

@@ -549,6 +549,7 @@ void scripting::on_entity_spawn(
     const dv::value& saved
 ) {
     auto L = lua::get_main_state();
+    lua::stackguard guard(L);
     lua::requireglobal(L, STDCOMP);
     if (lua::getfield(L, "new_Entity")) {
         lua::pushinteger(L, eid);