Bulk LBMs (#14954)

builtin/game/features.lua

@@ -43,6 +43,7 @@ core.features = {
 	moveresult_new_pos = true,
 	override_item_remove_fields = true,
 	hotbar_hud_element = true,
+	bulk_lbms = true,
 }
 
 function core.has_feature(arg)

builtin/game/misc.lua

@@ -298,3 +298,28 @@ do
 		return valid_object_iterator(core.get_objects_in_area(min_pos, max_pos))
 	end
 end
+
+--
+-- Helper for LBM execution, called from C++
+--
+
+function core.run_lbm(id, pos_list, dtime_s)
+	local lbm = core.registered_lbms[id]
+	assert(lbm, "Entry with given id not found in registered_lbms table")
+	core.set_last_run_mod(lbm.mod_origin)
+	if lbm.bulk_action then
+		return lbm.bulk_action(pos_list, dtime_s)
+	end
+	-- emulate non-bulk LBMs
+	local expect = core.get_node(pos_list[1]).name
+	-- engine guarantees that
+	-- 1) all nodes are the same content type
+	-- 2) the list is up-to-date when we're called
+	assert(expect ~= "ignore")
+	for _, pos in ipairs(pos_list) do
+		local n = core.get_node(pos)
+		if n.name == expect then -- might have been changed by previous call
+			lbm.action(pos, n, dtime_s)
+		end
+	end
+end

builtin/game/register.lua

@@ -105,7 +105,12 @@ function core.register_lbm(spec)
 	-- Add to core.registered_lbms
 	check_modname_prefix(spec.name)
 	check_node_list(spec.nodenames, "nodenames")
-	assert(type(spec.action) == "function", "Required field 'action' of type function")
+	local have = spec.action ~= nil
+	local have_bulk = spec.bulk_action ~= nil
+	assert(not have or type(spec.action) == "function", "Field 'action' must be a function")
+	assert(not have_bulk or type(spec.bulk_action) == "function", "Field 'bulk_action' must be a function")
+	assert(have ~= have_bulk, "Either 'action' or 'bulk_action' must be present")
+
 	core.registered_lbms[#core.registered_lbms + 1] = spec
 	spec.mod_origin = core.get_current_modname() or "??"
 end