Re: How to convert to-be-closed variable to normal one in runtime?

[Mimmo Mane <pocomane_7a@...>]

On Tue, Jul 21, 2020 at 1:19 PM Egor Skriptunoff wrote:
> I have a problem while trying to use a to-be-closed variable as usual upvalue.
> An upvalue's lifespan might go beyond the current block, and the lifespan is unknown at compile time.
...
>       -- Now I want the file to remain opened after exiting from the current function
>       -- I need to de-<close>-ify the variable "logfile"
>       -- How can I do that?

Normally, you can declosify just overriding the __close() metamethod,
but here it is impossible without affecting the other files. You can
still use the proxy trick suggested by Andrew, or invert the logic:

```
local say = print

local function log_start_time()
   local logfile = assert(io.open("log.txt", "a"))

   local function write_to_log(msg)
      logfile:write(msg.."\n")
   end

   write_to_log("Started at "..os.date())
   if arg[1] ~= "--log-everything" then
     local please <close> = logfile
   else
      function say(msg)
         print(msg)
         write_to_log(msg)
      end
   end
end
```

About the sub-scope trick: in this case it would be simpler to just
call file:close() or getmetatable().__close(), however in some cases
you just can do it (`getmetatable().__metatable = "Not your buisness"`
with an ad-hoc __close() metamethod).