[Tarantool-patches] [PATCH V5 5.5/6] box: move Lua MP_EXT decoder from tuple.c

[Vladislav Shpilevoy]

Lua C module 'msgpack' supports registration of custom extension
decoders for MP_EXT values. That is needed to make 'msgpack' not
depending on any modules which use it.

So far the only extension were tuples - struct tuple cdata needed
to be encoded as an array.

That is going to change in next commits, where struct error cdata
appears. So the decoder can't be located in src/box/lua/tuple.c.
It is moved to a more common place - src/box/lua/init.c.

Needed for #4398

---
diff --git a/src/box/lua/init.c b/src/box/lua/init.c
index 63e8b8216..b05ff90be 100644
--- a/src/box/lua/init.c
+++ b/src/box/lua/init.c
@@ -36,6 +36,7 @@
 
 #include "lua/utils.h" /* luaT_error() */
 #include "lua/trigger.h"
+#include "lua/msgpack.h"
 
 #include "box/box.h"
 #include "box/txn.h"
@@ -386,6 +387,21 @@ static const struct luaL_Reg boxlib_backup[] = {
 	{NULL, NULL}
 };
 
+/**
+ * A MsgPack extensions handler, for types defined in box.
+ */
+static enum mp_type
+luamp_encode_extension_box(struct lua_State *L, int idx,
+			   struct mpstream *stream)
+{
+	struct tuple *tuple = luaT_istuple(L, idx);
+	if (tuple != NULL) {
+		tuple_to_mpstream(tuple, stream);
+		return MP_ARRAY;
+	}
+	return MP_EXT;
+}
+
 #include "say.h"
 
 void
@@ -426,6 +442,8 @@ box_lua_init(struct lua_State *L)
 	luaopen_merger(L);
 	lua_pop(L, 1);
 
+	luamp_set_encode_extension(luamp_encode_extension_box);
+
 	/* Load Lua extension */
 	for (const char **s = lua_sources; *s; s += 2) {
 		const char *modname = *s;
diff --git a/src/box/lua/tuple.c b/src/box/lua/tuple.c
index aba906d1f..03b4b8a2e 100644
--- a/src/box/lua/tuple.c
+++ b/src/box/lua/tuple.c
@@ -290,20 +290,6 @@ tuple_to_mpstream(struct tuple *tuple, struct mpstream *stream)
 	mpstream_advance(stream, bsize);
 }
 
-/* A MsgPack extensions handler that supports tuples */
-static enum mp_type
-luamp_encode_extension_box(struct lua_State *L, int idx,
-			   struct mpstream *stream)
-{
-	struct tuple *tuple = luaT_istuple(L, idx);
-	if (tuple != NULL) {
-		tuple_to_mpstream(tuple, stream);
-		return MP_ARRAY;
-	}
-
-	return MP_EXT;
-}
-
 /**
  * Convert a tuple into lua table. Named fields are stored as
  * {name = value} pairs. Not named fields are stored as
@@ -582,8 +568,6 @@ box_lua_tuple_init(struct lua_State *L)
 	luaL_register_module(L, tuplelib_name, lbox_tuplelib);
 	lua_pop(L, 1);
 
-	luamp_set_encode_extension(luamp_encode_extension_box);
-
 	tuple_serializer_update_options();
 	trigger_create(&tuple_serializer.update_trigger,
 		       on_msgpack_serializer_update, NULL, NULL);