Add table.key_value_swap (#9248)

builtin/common/misc_helpers.lua

@@ -575,6 +575,15 @@ function table.insert_all(t, other)
 end
 
 
+function table.key_value_swap(t)
+	local ti = {}
+	for k,v in pairs(t) do
+		ti[v] = k
+	end
+	return ti
+end
+
+
 --------------------------------------------------------------------------------
 -- mainmenu only functions
 --------------------------------------------------------------------------------

doc/lua_api.txt

@@ -2902,6 +2902,8 @@ Helper functions
 * `table.insert_all(table, other_table)`:
     * Appends all values in `other_table` to `table` - uses `#table + 1` to
       find new indices.
+* `table.key_value_swap(t)`: returns a table with keys and values swapped
+    * If multiple keys in `t` map to the same value, the result is undefined.
 * `minetest.pointed_thing_to_face_pos(placer, pointed_thing)`: returns a
   position.
     * returns the exact position on the surface of a pointed node