Set metatable to _preconnect when disconnected and add connected field

doc/irc.luadoc

@@ -130,6 +130,7 @@ function irc:shutdown()
 -- @name Connection
 -- @class table
 -- @field authed Boolean indicating whether the connection has completed registration.
+-- @field connected Whether the connection is currently connected.
 -- @field motd The server's message of the day.  Can be nil.
 -- @field nick The current nickname.
 -- @field realname The real name sent to the server.

init.lua

@@ -16,12 +16,15 @@ local meta_preconnect = {}
 function meta_preconnect.__index(o, k)
 	local v = rawget(meta_preconnect, k)
 
-	if not v and meta[k] then
+	if v == nil and meta[k] ~= nil then
 		error(("field '%s' is not accessible before connecting"):format(k), 2)
 	end
 	return v
 end
 
+meta.connected = true
+meta_preconnect.connected = false
+
 function new(data)
 	local o = {
 		nick = assert(data.nick, "Field 'nick' is required");
@@ -148,7 +151,7 @@ end
 
 function meta:shutdown()
 	self.socket:close()
-	setmetatable(self, nil)
+	setmetatable(self, meta_preconnect)
 end
 
 local function getline(self, errlevel)