Tramp hangs indefinitely when using doas on Linux

Question

Tramp works fine when I try to edit with sudo or ssh, but when I try to edit with doas it will hang (while also maxing out my cpu). Here is some tramp output:

  backtrace()
  tramp-signal-hook-function(quit (""))
  signal(quit (""))
  tramp-maybe-open-connection((tramp-file-name "doas" "root" nil "localhost" nil "/etc/doas.conf" nil))
  tramp-send-command((tramp-file-name "doas" "root" nil "localhost" nil "/etc/doas.conf" nil) "test 0 2>/dev/null; echo tramp_exit_status $?")
  tramp-send-command-and-check((tramp-file-name "doas" "root" nil "localhost" nil "/etc/doas.conf" nil) "test 0")
  tramp-get-test-command((tramp-file-name "doas" "root" nil "localhost" nil "/etc/doas.conf" nil))
  tramp-run-test("-d" "/doas:root@localhost:/etc/doas.conf")
  tramp-sh-handle-file-directory-p("/doas:root@localhost:/etc/doas.conf")
  apply(tramp-sh-handle-file-directory-p "/doas:root@localhost:/etc/doas.conf")
  tramp-sh-file-name-handler(file-directory-p "/doas:root@localhost:/etc/doas.conf")
  apply(tramp-sh-file-name-handler file-directory-p "/doas:root@localhost:/etc/doas.conf")
  tramp-file-name-handler(file-directory-p "/doas:root@localhost:/etc/doas.conf")
  file-directory-p("/doas:root@localhost:/etc/doas.conf")
  find-file-noselect("/doas:root@localhost:/etc/doas.conf" nil nil nil)
  find-alternate-file("/doas:root@localhost:/etc/doas.conf")
  (if (or arg (not buffer-file-name)) (find-file (concat "/doas:root@localhost:" (ido-read-file-name "Find file(as root): "))) (find-alternate-file (concat "/doas:root@localhost:" buffer-file-name)))
  er-doas-edit(nil)
  funcall-interactively(er-doas-edit nil)
  call-interactively(er-doas-edit record nil)
  command-execute(er-doas-edit record)
  execute-extended-command(nil "er-doas-edit" "er-do")
  funcall-interactively(execute-extended-command nil "er-doas-edit" "er-do")
  call-interactively(execute-extended-command nil nil)
  command-execute(execute-extended-command)

Tramp also made another buffer called debug Tramp/ doas root@Southpark which only contains this line:

11:05:44.458693 tramp-get-connection-property (7) # process-buffer nil

Here is Tramp's output to the message buffer:

Tramp: Opening connection for root@Southpark using doas...
Tramp: Sending command ‘exec doas -u root -s’
Tramp: Waiting for prompts from remote shell...failed
Tramp: Opening connection for root@Southpark using doas...failed

I set tramp-verbose to 10 and this was the output:

  backtrace()
  tramp-signal-hook-function(quit (""))
  signal(quit (""))
  tramp-maybe-open-connection((tramp-file-name "doas" #("root" 0 4 (tramp-default t)) nil #("Southpark" 0 9 (tramp-default t)) nil "/lol" nil))
  tramp-send-command((tramp-file-name "doas" #("root" 0 4 (tramp-default t)) nil #("Southpark" 0 9 (tramp-default t)) nil "/lol" nil) "/bin/test -e / 2>/dev/null; echo tramp_exit_status...")
  tramp-send-command-and-check((tramp-file-name "doas" #("root" 0 4 (tramp-default t)) nil #("Southpark" 0 9 (tramp-default t)) nil "/lol" nil) "/bin/test -e /")
  tramp-find-file-exists-command((tramp-file-name "doas" #("root" 0 4 (tramp-default t)) nil #("Southpark" 0 9 (tramp-default t)) nil "/lol" nil))
  tramp-get-file-exists-command((tramp-file-name "doas" #("root" 0 4 (tramp-default t)) nil #("Southpark" 0 9 (tramp-default t)) nil "/lol" nil))
  tramp-sh-handle-file-exists-p(#("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)))
  apply(tramp-sh-handle-file-exists-p #("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)))
  tramp-sh-file-name-handler(file-exists-p #("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)))
  apply(tramp-sh-file-name-handler file-exists-p #("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)))
  tramp-file-name-handler(file-exists-p #("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)))
  file-exists-p(#("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)))
  completion-file-name-table(#("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)) file-exists-p lambda)
  test-completion(#("/doas:root@Southpark:/lol" 6 10 (tramp-default t) 11 20 (tramp-default t)) completion-file-name-table file-exists-p)
  completion--file-name-table("/doas::/lol" file-exists-p lambda)
  complete-with-action(lambda completion--file-name-table "/doas::/lol" file-exists-p)
  #f(compiled-function (table) #<bytecode 0x156dc8a263a1>)(completion--file-name-table)
  completion--some(#f(compiled-function (table) #<bytecode 0x156dc8a263a1>) (completion--embedded-envvar-table completion--file-name-table))
  read-file-name-internal("/doas::/lol" file-exists-p lambda)
  test-completion("/doas::/lol" read-file-name-internal file-exists-p)
  completion--complete-and-exit(12 23 exit-minibuffer #f(compiled-function () #<bytecode 0x156dc8a26381>))
  completion-complete-and-exit(12 23 exit-minibuffer)
  minibuffer-complete-and-exit()
  funcall-interactively(minibuffer-complete-and-exit)
  call-interactively(minibuffer-complete-and-exit nil nil)
  command-execute(minibuffer-complete-and-exit)
  read-from-minibuffer("Find file: " "~/" (keymap (keymap (32)) keymap (10 . minibuffer-complete-and-exit) (13 . minibuffer-complete-and-exit) keymap (menu-bar keymap (minibuf "Minibuf" keymap (tab menu-item "Complete" minibuffer-complete :help "Complete as far as possible") (space menu-item "Complete Word" minibuffer-complete-word :help "Complete at most one word") (63 menu-item "List Completions" minibuffer-completion-help :help "Display all possible completions") "Minibuf")) (27 keymap (118 . switch-to-completions)) (prior . switch-to-completions) (63 . minibuffer-completion-help) (32 . minibuffer-complete-word) (9 . minibuffer-complete) keymap (menu-bar keymap (minibuf "Minibuf" keymap (previous menu-item "Previous History Item" previous-history-element :help "Put previous minibuffer history element in the min...") (next menu-item "Next History Item" next-history-element :help "Put next minibuffer history element in the minibuf...") (isearch-backward menu-item "Isearch History Backward" isearch-backward :help "Incrementally search minibuffer history backward") (isearch-forward menu-item "Isearch History Forward" isearch-forward :help "Incrementally search minibuffer history forward") (return menu-item "Enter" exit-minibuffer :key-sequence "\15" :help "Terminate input and exit minibuffer") (quit menu-item "Quit" abort-recursive-edit :help "Abort input and exit minibuffer") "Minibuf")) (10 . exit-minibuffer) (13 . exit-minibuffer) (7 . minibuffer-keyboard-quit) (C-tab . file-cache-minibuffer-complete) (9 . self-insert-command) (XF86Back . previous-history-element) (up . previous-line-or-history-element) (prior . previous-history-element) (XF86Forward . next-history-element) (down . next-line-or-history-element) (next . next-history-element) (27 keymap (60 . minibuffer-beginning-of-buffer) (114 . previous-matching-history-element) (115 . next-matching-history-element) (112 . previous-history-element) (110 . next-history-element))) nil file-name-history "~/" nil)
  completing-read-default("Find file: " read-file-name-internal file-exists-p confirm-after-completion "~/" file-name-history "~/" nil)
  completing-read("Find file: " read-file-name-internal file-exists-p confirm-after-completion "~/" file-name-history "~/")
  read-file-name-default("Find file: " nil "~/" confirm-after-completion nil nil)
  read-file-name("Find file: " nil "~/" confirm-after-completion)
  find-file-read-args("Find file: " confirm-after-completion)
  byte-code("\300\301\302 \"\207" [find-file-read-args "Find file: " confirm-nonexistent-file-or-buffer] 3)
  call-interactively(joe-edit nil nil)
  command-execute(joe-edit)

And the debug tramp/doas root@Southpark buffer was enormous, se here's the first few dozen lines

;; Emacs: 27.1 Tramp: 2.4.3.27.1 -*- mode: outline; -*-
;; Location: /usr/share/emacs/27.1/lisp/net/tramp.elc Git: /
11:05:39.354574 tramp-get-file-property (8) # /lol file-exists-p undef
11:05:39.354639 tramp-get-file-property (8) # /lol file-attributes-integer nil
11:05:39.354685 tramp-get-file-property (8) # /lol file-attributes-string nil
11:05:39.354721 tramp-get-connection-property (7) # file-exists undef
11:05:39.354752 tramp-get-file-exists-command (5) # Finding command to check if file exists
11:05:39.354812 tramp-get-connection-property (7) # test undef
11:05:39.354847 tramp-get-test-command (5) # Finding a suitable ‘test’ command
11:05:39.354886 tramp-get-connection-property (7) # process-name nil
11:05:39.354921 tramp-get-connection-property (7) # process-name nil
11:05:39.354952 tramp-get-connection-property (7) # process-buffer nil
11:05:39.354990 tramp-get-connection-property (7) # process-buffer nil
11:05:39.355020 tramp-set-connection-property (7) # process-buffer nil
11:05:39.355090 tramp-maybe-open-connection (3) # Opening connection for root@Southpark using doas...
11:05:39.355176 tramp-call-process (6) # ‘locale -a’ nil  *temp*
11:05:39.355887 tramp-call-process (6) # 0
C
en_US.utf8
ja_JP
ja_JP.eucjp
ja_JP.ujis
ja_JP.utf8
japanese
japanese.euc
POSIX
11:05:39.355948 tramp-get-local-locale (7) # locale en_US.utf8
11:05:39.356016 tramp-get-connection-property (7) # login-args undef
11:05:39.356063 tramp-get-connection-property (7) # login-args undef
11:05:39.356112 tramp-get-connection-property (7) # process-name nil
11:05:39.356151 tramp-get-connection-property (7) # process-buffer nil
11:05:39.356394 tramp-maybe-open-connection (6) # /bin/sh -i
11:05:39.356447 tramp-get-connection-property (7) # check-remote-echo nil
11:05:39.356482 tramp-get-connection-property (7) # check-remote-echo nil
11:05:39.362229 tramp-accept-process-output (10) # *tramp/doas root@Southpark* nil run t
#$ 
11:05:39.362301 tramp-get-connection-property (7) # check-remote-echo nil
11:05:39.362341 tramp-get-connection-property (7) # check-remote-echo nil
11:05:39.362390 tramp-wait-for-regexp (6) # 
#$ 
11:05:39.362439 tramp-get-connection-property (7) # login-program undef
11:05:39.362485 tramp-get-connection-property (7) # login-args undef
11:05:39.362529 tramp-get-connection-property (7) # remote-shell undef
11:05:39.362574 tramp-get-connection-property (7) # async-args undef
11:05:39.362618 tramp-get-connection-property (7) # connection-timeout undef
11:05:39.362658 tramp-get-connection-property (7) # temp-file undef
11:05:39.362738 tramp-set-connection-property (7) # temp-file /tmp/tramp.LaiDu1
11:05:39.362779 tramp-set-connection-property (7) # password-vector (tramp-file-name doas root nil Southpark nil nil nil)
11:05:39.362829 tramp-get-connection-property (7) # session-timeout undef
11:05:39.362872 tramp-get-connection-property (7) # session-timeout undef
11:05:39.362910 tramp-set-connection-property (7) # session-timeout 300
11:05:39.363072 tramp-maybe-open-connection (3) # Sending command ‘exec doas -u root -s’
11:05:39.363120 tramp-get-connection-property (7) # process-name nil
11:05:39.363162 tramp-get-connection-property (7) # remote-echo nil
11:05:39.363197 tramp-send-command (6) # exec doas -u root -s
11:05:39.363240 tramp-get-connection-property (7) # process-name nil
11:05:39.363280 tramp-get-connection-property (7) # chunksize nil
11:05:39.363317 tramp-set-connection-property (7) # last-cmd-time (24604 17795 363305 774000)
11:05:39.363358 tramp-send-string (10) # exec doas -u root -s
11:05:39.363397 tramp-get-connection-property (7) # process-buffer nil
11:05:39.363454 tramp-get-connection-property (7) # password-vector (tramp-file-name doas root nil Southpark nil nil nil)
11:05:39.363499 tramp-set-connection-property (7) # first-password-request 
11:05:39.363548 tramp-process-actions (3) # Waiting for prompts from remote shell...
11:05:39.363641 tramp-accept-process-output (10) # *tramp/doas root@Southpark* 0 run nil

This happens when I try to run the following er-doas-edit edit function on the (already opened) /etc/doas.conf.

(defun er-doas-edit (&optional arg)
  "Edit currently visited file as root With a prefix ARG prompt for a file to visit.
Will also prompt for a file to visit if current buffer is not visiting a file."
  (interactive "P")
  (if (or arg (not buffer-file-name))
      (find-file (concat "/doas:root@localhost:"
                         (ido-read-file-name "Find file(as root): ")))
    (find-alternate-file (concat "/doas:root@localhost:" buffer-file-name))))

The same error happens no matter how I try to open the file with doas.

I'm on Arch Linux.

emacs --version reports: GNU Emacs 27.1

Here is the full tramp debug buffer

Answer 1

See line 178058 of the debug output. Your prompt is not understandable by Tramp, I suppose zsh is in game. Pls read the Tramp manual how to configure zsh properly.