[PATCH 2/5] lua: port console yaml formatting to C

[Vladimir Davydov]

On Mon, Mar 19, 2018 at 04:34:49PM +0300, Vladislav Shpilevoy wrote:
> Box.session.push() will be implemented in C lbox_session_push()
> function, which will use port to encapsulate different session
> types (binary, text) push() logic. And push() must be able to
> either encode an argument into message pack, or format it as a
> string using yaml. This formatting can not be done in Lua before
> push() call, since it breaks push() virtualization.
> 
> Needed for #2677
> 
> Signed-off-by: Vladislav Shpilevoy <v.shpilevoy at tarantool.org>
> ---
>  src/box/lua/console.c         | 42 ++++++++++++++++++++++++++++++++++++++++++
>  src/box/lua/console.lua       | 34 ++++++++--------------------------
>  third_party/lua-yaml/lyaml.cc |  9 +++------
>  third_party/lua-yaml/lyaml.h  |  3 +++
>  4 files changed, 56 insertions(+), 32 deletions(-)
> 
> diff --git a/src/box/lua/console.c b/src/box/lua/console.c

> @@ -328,6 +329,32 @@ lbox_console_add_history(struct lua_State *L)
>  	return 0;
>  }
>  
> +static int
> +lbox_console_format(struct lua_State *L)
> +{
> +	int arg_count = lua_gettop(L);
> +	if (arg_count == 0) {
> +		lua_pushstring(L, "---\n...\n");
> +		return 1;
> +	}
> +	lua_getfield(L, LUA_REGISTRYINDEX, "_LOADED");
> +	lua_getfield(L, -1, "console");
> +	lua_getfield(L, -1, "formatter");
> +	lua_getfield(L, -1, "encode");
> +	lua_createtable(L, arg_count, 0);
> +	for (int i = 0; i < arg_count; ++i) {
> +		if (lua_isnil(L, i + 1))
> +			lua_getfield(L, -3, "NULL");
> +		else
> +			lua_pushvalue(L, i + 1);
> +		lua_rawseti(L, -2, i + 1);
> +	}
> +	lua_call(L, 1, 1);
> +	lua_insert(L, -4);
> +	lua_pop(L, 3);
> +	return 1;
> +}
> +
>  void
>  tarantool_lua_console_init(struct lua_State *L)
>  {

> @@ -344,6 +372,20 @@ tarantool_lua_console_init(struct lua_State *L)
>  	lua_getfield(L, -1, "completion_handler");
>  	lua_pushcclosure(L, lbox_console_readline, 1);
>  	lua_setfield(L, -2, "readline");
> +
> +	lua_yaml_new_formatter(L);
> +	lua_getfield(L, -1, "cfg");
> +	lua_createtable(L, 0, 4);
> +	lua_pushboolean(L, true);
> +	lua_setfield(L, -2, "encode_invalid_numbers");
> +	lua_pushboolean(L, true);
> +	lua_setfield(L, -2, "encode_load_metatables");
> +	lua_pushboolean(L, true);
> +	lua_setfield(L, -2, "encode_use_tostring");
> +	lua_pushboolean(L, true);
> +	lua_setfield(L, -2, "encode_invalid_as_nil");
> +	lua_call(L, 1, 0);
> +	lua_setfield(L, -2, "formatter");

> diff --git a/src/box/lua/console.lua b/src/box/lua/console.lua
> @@ -395,4 +375,6 @@ package.loaded['console'] = {
>      on_start = on_start;
>      on_client_disconnect = on_client_disconnect;
>      completion_handler = internal.completion_handler;
> +    formatter = internal.formatter;

I don't like that we export the serializer to Lua, but never use it in
Lua code, only in C. Can't we create a serializer in C and pass it to
the encoder function explicitly?