If idris2 --ide-mode-socket is already running, idris2-run mistakenly tries to connect to port 98

[rntz]

Ubuntu 22.04 LTS
GNU Emacs 27.1
Idris version 0.5.1-68a144bf1

If I already have idris2 --ide-mode-socket running somewhere, running it again produces an error message:

$ idris2 --ide-mode-socket &
38398
$ idris2 --ide-mode-socket
Failed to bind socket with error: 98

If, while I have idris2 --ide-mode-socket running elsewhere, I try idris2-run in Emacs, I see this error:

Warning from Idris2: Failed to bind socket with error: 
error in process filter: open-network-stream: make client process failed: Connection refused, :name, Idris2 IDE support, :buffer, *idris2-connection*, :host, 127.0.0.1, :service, 98, :nowait, nil, :tls-parameters, nil
error in process filter: make client process failed: Connection refused, :name, Idris2 IDE support, :buffer, *idris2-connection*, :host, 127.0.0.1, :service, 98, :nowait, nil, :tls-parameters, nil
Idris2 disconnected: exited abnormally with code 1

This is a bit strange. What seems to be happening is that idris2-process-filter has a bug or misfeature:

(defun idris2-process-filter (string)
  "Accept output from the process"
  (if idris2-connection
      string
    ;; Idris2 sometimes prints a warning prior to the port number, which causes
    ;; `string-match' to return 0
    (cl-flet ((idris2-warn (msg)
                          (unless (or (null msg) (string-blank-p msg))
                            (message "Warning from Idris2: %s" msg))))
      (if (not (string-match idris2-process-port-output-regexp string))
          (idris2-warn string)
        (idris2-warn (match-string 1 string))
        (idris2-connect (string-to-number (match-string 2 string))))
      "")))

Here, string gets bound to "Failed to bind socket with error: 98\n". Then string-match succeeds (returning 0) because there is indeed a number in this string and idris2-process-port-output-regexp is not start-/end-anchored. So we take the second branch, warn about the part of the string before the number, and interpret 98 as a port number. Unfortunately, it isn't.

The simplest way to fix this would be to anchor idris2-process-port-output-regexp (add ^ to beginning and $ to the end). Unfortunately, the way the code is written suggests there's some case where idris2 --ide-mode-socket produces a warning followed by a genuine port number. I'm not sure what this case is, so I don't know the best way to distinguish between that case and this one.

I think I ran into this problem because I had tried loading a file with idris-mode, which had managed to start an idris2 process but had some unrelated problem, so I tried installing idris2-mode and when I tried to load the file with idris2-mode, the old process was still around.

It also seems unfortunate that idris2 --ide-mode-socket fails if a copy is already running, I'll try to report that upstream.

[dunhamsteve]

This issue should be fixed upstream now. When you get a chance, can you verify with a recent build from the main branch of Idris2?