Refactor Lua metatable initialization

src/flex-lua-expire-output.cpp

@@ -99,31 +99,14 @@ int setup_flex_expire_output(lua_State *lua_state,
  */
 void lua_wrapper_expire_output::init(lua_State *lua_state)
 {
-    lua_getglobal(lua_state, "osm2pgsql");
-    if (luaL_newmetatable(lua_state, OSM2PGSQL_EXPIRE_OUTPUT_CLASS) != 1) {
-        throw std::runtime_error{"Internal error: Lua newmetatable failed."};
-    }
-    lua_pushvalue(lua_state, -1); // Copy of new metatable
-
-    // Add metatable as osm2pgsql.ExpireOutput so we can access it from Lua
-    lua_setfield(lua_state, -3, "ExpireOutput");
-
-    // Now add functions to metatable
-    lua_pushvalue(lua_state, -1);
-    lua_setfield(lua_state, -2, "__index");
-    luaX_add_table_func(lua_state, "__tostring",
-                        lua_trampoline_expire_output_tostring);
-    luaX_add_table_func(lua_state, "filename",
-                        lua_trampoline_expire_output_filename);
-    luaX_add_table_func(lua_state, "maxzoom",
-                        lua_trampoline_expire_output_maxzoom);
-    luaX_add_table_func(lua_state, "minzoom",
-                        lua_trampoline_expire_output_minzoom);
-    luaX_add_table_func(lua_state, "schema",
-                        lua_trampoline_expire_output_schema);
-    luaX_add_table_func(lua_state, "table", lua_trampoline_expire_output_table);
-
-    lua_pop(lua_state, 2);
+    luaX_set_up_metatable(
+        lua_state, "ExpireOutput", OSM2PGSQL_EXPIRE_OUTPUT_CLASS,
+        {{"__tostring", lua_trampoline_expire_output_tostring},
+         {"filename", lua_trampoline_expire_output_filename},
+         {"maxzoom", lua_trampoline_expire_output_maxzoom},
+         {"minzoom", lua_trampoline_expire_output_minzoom},
+         {"schema", lua_trampoline_expire_output_schema},
+         {"table", lua_trampoline_expire_output_table}});
 }
 
 int lua_wrapper_expire_output::tostring() const

src/flex-lua-geom.cpp

@@ -300,37 +300,25 @@ int geom_transform(lua_State *lua_state)
 
 void init_geometry_class(lua_State *lua_state)
 {
-    lua_getglobal(lua_state, "osm2pgsql");
-    if (luaL_newmetatable(lua_state, OSM2PGSQL_GEOMETRY_CLASS) != 1) {
-        throw std::runtime_error{"Internal error: Lua newmetatable failed."};
-    }
-    lua_pushvalue(lua_state, -1); // Copy of new metatable
-
-    // Add metatable as osm2pgsql.Geometry so we can access it from Lua
-    lua_setfield(lua_state, -3, "Geometry");
-
-    luaX_add_table_func(lua_state, "__gc", geom_gc);
-    luaX_add_table_func(lua_state, "__len", geom_num_geometries);
-    luaX_add_table_func(lua_state, "__tostring", geom_tostring);
-    lua_pushvalue(lua_state, -1);
-    lua_setfield(lua_state, -2, "__index");
-    luaX_add_table_func(lua_state, "area", geom_area);
-    luaX_add_table_func(lua_state, "length", geom_length);
-    luaX_add_table_func(lua_state, "centroid", geom_centroid);
-    luaX_add_table_func(lua_state, "get_bbox", geom_get_bbox);
-    luaX_add_table_func(lua_state, "geometry_n", geom_geometry_n);
-    luaX_add_table_func(lua_state, "geometry_type", geom_geometry_type);
-    luaX_add_table_func(lua_state, "is_null", geom_is_null);
-    luaX_add_table_func(lua_state, "line_merge", geom_line_merge);
-    luaX_add_table_func(lua_state, "reverse", geom_reverse);
-    luaX_add_table_func(lua_state, "num_geometries", geom_num_geometries);
-    luaX_add_table_func(lua_state, "pole_of_inaccessibility",
-                        geom_pole_of_inaccessibility);
-    luaX_add_table_func(lua_state, "segmentize", geom_segmentize);
-    luaX_add_table_func(lua_state, "simplify", geom_simplify);
-    luaX_add_table_func(lua_state, "spherical_area", geom_spherical_area);
-    luaX_add_table_func(lua_state, "srid", geom_srid);
-    luaX_add_table_func(lua_state, "transform", geom_transform);
-
-    lua_pop(lua_state, 2); // __index, global osmp2gsql
+    luaX_set_up_metatable(
+        lua_state, "Geometry", OSM2PGSQL_GEOMETRY_CLASS,
+        {{"__gc", geom_gc},
+         {"__len", geom_num_geometries},
+         {"__tostring", geom_tostring},
+         {"area", geom_area},
+         {"length", geom_length},
+         {"centroid", geom_centroid},
+         {"get_bbox", geom_get_bbox},
+         {"geometry_n", geom_geometry_n},
+         {"geometry_type", geom_geometry_type},
+         {"is_null", geom_is_null},
+         {"line_merge", geom_line_merge},
+         {"reverse", geom_reverse},
+         {"num_geometries", geom_num_geometries},
+         {"pole_of_inaccessibility", geom_pole_of_inaccessibility},
+         {"segmentize", geom_segmentize},
+         {"simplify", geom_simplify},
+         {"spherical_area", geom_spherical_area},
+         {"srid", geom_srid},
+         {"transform", geom_transform}});
 }

src/flex-lua-locator.cpp

@@ -70,30 +70,14 @@ void lua_wrapper_locator::init(lua_State *lua_state,
 {
     s_connection_params = connection_params;
 
-    lua_getglobal(lua_state, "osm2pgsql");
-    if (luaL_newmetatable(lua_state, OSM2PGSQL_LOCATOR_CLASS) != 1) {
-        throw std::runtime_error{"Internal error: Lua newmetatable failed."};
-    }
-    lua_pushvalue(lua_state, -1); // Copy of new metatable
-
-    // Add metatable as osm2pgsql.Locator so we can access it from Lua
-    lua_setfield(lua_state, -3, "Locator");
-
-    // Now add functions to metatable
-    lua_pushvalue(lua_state, -1);
-    lua_setfield(lua_state, -2, "__index");
-    luaX_add_table_func(lua_state, "__tostring",
-                        lua_trampoline_locator_tostring);
-    luaX_add_table_func(lua_state, "name", lua_trampoline_locator_name);
-    luaX_add_table_func(lua_state, "add_bbox", lua_trampoline_locator_add_bbox);
-    luaX_add_table_func(lua_state, "add_from_db",
-                        lua_trampoline_locator_add_from_db);
-    luaX_add_table_func(lua_state, "all_intersecting",
-                        lua_trampoline_locator_all_intersecting);
-    luaX_add_table_func(lua_state, "first_intersecting",
-                        lua_trampoline_locator_first_intersecting);
-
-    lua_pop(lua_state, 2);
+    luaX_set_up_metatable(
+        lua_state, "Locator", OSM2PGSQL_LOCATOR_CLASS,
+        {{"__tostring", lua_trampoline_locator_tostring},
+         {"name", lua_trampoline_locator_name},
+         {"add_bbox", lua_trampoline_locator_add_bbox},
+         {"add_from_db", lua_trampoline_locator_add_from_db},
+         {"all_intersecting", lua_trampoline_locator_all_intersecting},
+         {"first_intersecting", lua_trampoline_locator_first_intersecting}});
 }
 
 int lua_wrapper_locator::tostring() const

src/flex-lua-table.cpp

@@ -457,27 +457,13 @@ int setup_flex_table(lua_State *lua_state, std::vector<flex_table_t> *tables,
  */
 void lua_wrapper_table::init(lua_State *lua_state)
 {
-    lua_getglobal(lua_state, "osm2pgsql");
-    if (luaL_newmetatable(lua_state, OSM2PGSQL_TABLE_CLASS) != 1) {
-        throw std::runtime_error{"Internal error: Lua newmetatable failed."};
-    }
-    lua_pushvalue(lua_state, -1); // Copy of new metatable
-
-    // Add metatable as osm2pgsql.Table so we can access it from Lua
-    lua_setfield(lua_state, -3, "Table");
-
-    // Now add functions to metatable
-    lua_pushvalue(lua_state, -1);
-    lua_setfield(lua_state, -2, "__index");
-    luaX_add_table_func(lua_state, "__tostring",
-                        lua_trampoline_table_tostring);
-    luaX_add_table_func(lua_state, "insert", lua_trampoline_table_insert);
-    luaX_add_table_func(lua_state, "name", lua_trampoline_table_name);
-    luaX_add_table_func(lua_state, "schema", lua_trampoline_table_schema);
-    luaX_add_table_func(lua_state, "cluster", lua_trampoline_table_cluster);
-    luaX_add_table_func(lua_state, "columns", lua_trampoline_table_columns);
-
-    lua_pop(lua_state, 2);
+    luaX_set_up_metatable(lua_state, "Table", OSM2PGSQL_TABLE_CLASS,
+                          {{"__tostring", lua_trampoline_table_tostring},
+                           {"insert", lua_trampoline_table_insert},
+                           {"name", lua_trampoline_table_name},
+                           {"schema", lua_trampoline_table_schema},
+                           {"cluster", lua_trampoline_table_cluster},
+                           {"columns", lua_trampoline_table_columns}});
 }
 
 int lua_wrapper_table::tostring() const

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/lua-utils.cpp

@@ -115,6 +115,32 @@ void luaX_add_table_func(lua_State *lua_state, char const *key,
     lua_rawset(lua_state, -3);
 }
 
+void luaX_set_up_metatable(
+    lua_State *lua_state, char const *name, char const *luaclass,
+    std::initializer_list<std::pair<char const *, lua_CFunction>> map)
+
+{
+    lua_getglobal(lua_state, "osm2pgsql");
+    if (luaL_newmetatable(lua_state, luaclass) != 1) {
+        throw std::runtime_error{"Internal error: Lua newmetatable failed."};
+    }
+    lua_pushvalue(lua_state, -1); // Copy of new metatable
+
+    // Add metatable under the specified name so we can access it from Lua
+    lua_setfield(lua_state, -3, name);
+
+    // Now add functions to metatable
+    lua_pushvalue(lua_state, -1);
+    lua_setfield(lua_state, -2, "__index");
+    for (auto const &[key, func] : map) {
+        lua_pushstring(lua_state, key);
+        lua_pushcfunction(lua_state, func);
+        lua_rawset(lua_state, -3);
+    }
+
+    lua_settop(lua_state, 0);
+}
+
 char const *luaX_get_table_string(lua_State *lua_state, char const *key,
                                   int table_index, char const *error_msg)
 {

src/lua-utils.hpp

@@ -17,6 +17,7 @@
 
 #include <cassert>
 #include <cstdint>
+#include <initializer_list>
 #include <string_view>
 #include <utility>
 
@@ -38,6 +39,10 @@ void luaX_add_table_bool(lua_State *lua_state, char const *key,
 void luaX_add_table_func(lua_State *lua_state, char const *key,
                          lua_CFunction func) noexcept;
 
+void luaX_set_up_metatable(
+    lua_State *lua_state, char const *name, char const *luaclass,
+    std::initializer_list<std::pair<char const *, lua_CFunction>> map);
+
 template <typename COLLECTION, typename FUNC>
 void luaX_add_table_array(lua_State *lua_state, char const *key,
                           COLLECTION const &collection, FUNC const &func)

src/output-flex.cpp

@@ -1305,45 +1305,23 @@ void output_flex_t::init_lua(std::string const &filename,
 
     assert(lua_gettop(lua_state()) == 0);
 
+    luaX_set_up_metatable(
+        lua_state(), "OSMObject", OSM2PGSQL_OSMOBJECT_CLASS,
+        {{"get_bbox", lua_trampoline_app_get_bbox},
+         {"as_linestring", lua_trampoline_app_as_linestring},
+         {"as_point", lua_trampoline_app_as_point},
+         {"as_polygon", lua_trampoline_app_as_polygon},
+         {"as_multipoint", lua_trampoline_app_as_multipoint},
+         {"as_multilinestring", lua_trampoline_app_as_multilinestring},
+         {"as_multipolygon", lua_trampoline_app_as_multipolygon},
+         {"as_geometrycollection", lua_trampoline_app_as_geometrycollection}});
+
     // 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));
     }
 
-    // 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");
-    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);
-    luaX_add_table_func(lua_state(), "as_point",
-                        lua_trampoline_app_as_point);
-    luaX_add_table_func(lua_state(), "as_polygon",
-                        lua_trampoline_app_as_polygon);
-    luaX_add_table_func(lua_state(), "as_multipoint",
-                        lua_trampoline_app_as_multipoint);
-    luaX_add_table_func(lua_state(), "as_multilinestring",
-                        lua_trampoline_app_as_multilinestring);
-    luaX_add_table_func(lua_state(), "as_multipolygon",
-                        lua_trampoline_app_as_multipolygon);
-    luaX_add_table_func(lua_state(), "as_geometrycollection",
-                        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 user config file
     luaX_set_context(lua_state(), this);
     if (luaL_dofile(lua_state(), filename.c_str())) {