Simplify setup of OSMObject Lua metatable

Uses the same mechanism as the other metatables now.

Author: joto

src/init.lua

@@ -176,20 +176,16 @@ function osm2pgsql.split_string(str, separator)
     return result
 end
 
--- This will be the metatable for the OSM objects given to the process callback
--- functions.
-object_metatable = {
-    __index =  {
-        grab_tag = function(data, tag)
-            if not tag then
-                error("Missing tag key", 2)
-            end
-            local v = data.tags[tag]
-            data.tags[tag] = nil
-            return v
+if osm2pgsql.OSMObject then
+    osm2pgsql.OSMObject.__index.grab_tag = function(data, tag)
+        if not tag then
+            error("Missing tag key", 2)
         end
-    }
-}
+        local v = data.tags[tag]
+        data.tags[tag] = nil
+        return v
+    end
+end
 
 -- This is used to iterate over (multi)geometries.
 function osm2pgsql.Geometry.geometries(geom)

src/output-flex.cpp

@@ -1305,17 +1305,17 @@ void output_flex_t::init_lua(std::string const &filename,
 
     assert(lua_gettop(lua_state()) == 0);
 
-    // Load compiled in init.lua
-    if (luaL_dostring(lua_state(), lua_init())) {
-        throw fmt_error("Internal error in Lua setup: {}.",
-                        lua_tostring(lua_state(), -1));
+    lua_getglobal(lua_state(), "osm2pgsql");
+    if (luaL_newmetatable(lua_state(), OSM2PGSQL_OSMOBJECT_CLASS) != 1) {
+        throw std::runtime_error{"Internal error: Lua newmetatable failed."};
     }
+    lua_pushvalue(lua_state(), -1); // Copy of new metatable
+
+    // Add metatable as osm2pgsql.OSMObject so we can access it from Lua
+    lua_setfield(lua_state(), -3, "OSMObject");
 
-    // Store the methods on OSM objects in its metatable.
-    lua_getglobal(lua_state(), "object_metatable");
-    lua_pushstring(lua_state(), OSM2PGSQL_OSMOBJECT_CLASS);
-    lua_setfield(lua_state(), -2, "__name");
-    lua_getfield(lua_state(), -1, "__index");
+    lua_pushvalue(lua_state(), -1);
+    lua_setfield(lua_state(), -2, "__index");
     luaX_add_table_func(lua_state(), "get_bbox", lua_trampoline_app_get_bbox);
     luaX_add_table_func(lua_state(), "as_linestring",
                         lua_trampoline_app_as_linestring);
@@ -1333,16 +1333,11 @@ void output_flex_t::init_lua(std::string const &filename,
                         lua_trampoline_app_as_geometrycollection);
     lua_settop(lua_state(), 0);
 
-    // Store the global object "object_metatable" defined in the init.lua
-    // script in the registry and then remove the global object. It will
-    // later be used as metatable for OSM objects.
-    lua_pushstring(lua_state(), OSM2PGSQL_OSMOBJECT_CLASS);
-    lua_getglobal(lua_state(), "object_metatable");
-    lua_settable(lua_state(), LUA_REGISTRYINDEX);
-    lua_pushnil(lua_state());
-    lua_setglobal(lua_state(), "object_metatable");
-
-    assert(lua_gettop(lua_state()) == 0);
+    // Load compiled in init.lua
+    if (luaL_dostring(lua_state(), lua_init())) {
+        throw fmt_error("Internal error in Lua setup: {}.",
+                        lua_tostring(lua_state(), -1));
+    }
 
     // Load user config file
     luaX_set_context(lua_state(), this);