Make --eval print values to the shell

[aartaka]

This would allow to create Nyxt front-ends (like the one discussed on IRC recently) and have better shell interaction in general.

[aartaka]

Command that doesn't print anything, even though it should:
nyxt --remote --eval '(nyxt:current-buffer)'

[Ambrevar]

Any idea how to do this?

For now all I have in mind is that the remote evaluator should open its own temporary socket and send 2 commands to the server: 1 with the remote socket information, 1 with the actual command.
Then when the server is done, it writes to the remote socket.
The remote evaluator listens to its socket and upon reception it closes it, outputs the result to stdout and exits.

There must be a simpler way though, no?
Any idea what emacsclient does?

[Ambrevar]

Forget what I said: Unix sockets are bidrectional, this works:

(iolib:with-open-socket (s :address-family :local :remote-filename "foo.socket")
  (write-string "foo" s)
  (read-line s))

and on the Nyxt server side, write to the accepted connection.
Don't forget to flush.

[aadcg]

I don't see any issues here. It does seem to print values to stdout.

$ nyxt --remote --quit --eval '4'

(process:31943): Gtk-WARNING **: 16:16:17.309: Locale not supported by C library.
	Using the fallback 'C' locale.
<INFO> [16:16:17] Probing remote instance listening to /run/user/1000/nyxt/nyxt.socket.
<INFO> [16:16:17] External evaluation request: "4"
4

$ nyxt --remote --quit --eval '(nyxt:current-buffer)'

(process:31964): Gtk-WARNING **: 16:16:35.845: Locale not supported by C library.
	Using the fallback 'C' locale.
<INFO> [16:16:35] Probing remote instance listening to /run/user/1000/nyxt/nyxt.socket.
<INFO> [16:16:35] External evaluation request: "(nyxt:current-buffer)"
#<WEB-BUFFER 1665 {1007EDB4C3}>

EDIT: The above works because nyxt and nyxt --remote were both issued under the same shell process. When that's not the case, the output is written to stout of the shell that started nyxt. Interesting!

Then this is a bug, not a feature request.

[aartaka]

Yes, that's a bug.

[aadcg]

I'm not sure how to fix this bug since I don't know much about Unix sockets. My primitive understanding is that when we connect to the socket and send a sexp (nyxt --server --eval ...) we need to set the right output stream since, by default, it will pick the *standard-output* from the moment when nyxt (not the server) was started.

[Ambrevar]

I don't think it's a bug: the nyxt server instance prints to its stdout, so if the remote instance is in the same shell, it's only normal that that result is printed in the same shell.

To fix this, we need to go as I mentioned in #1453 (comment), but sionescu/iolib#79 is kind of blocking here.