bug#64278: 29.0.92; tramp-rclone.el seems to be in a defunct state

[Sebastian Miele]

I am using the Tramp built into the most recent emacs-29 from the Emacs
repository.  Steps to reproduce the first problem:

Augment ~/.config/rclone/rclone.conf with:

  [memory]
  type = memory

Run:

  rm -rf ~/.emacs ~/.emacs.d && src/emacs -Q -l $DEBUG

The content of $DEBUG probably is not essential to this bug.  It
contains:

  (setq native-comp-jit-compilation nil)
  (setq load-prefer-newer t)
  (setq tramp-verbose 10)

Then write

  (find "/rclone:memory:/")

into the *scratch* buffer and evaluate it using C-x C-e.

After a while, a backtrace for an error "Lisp nesting exceeds
‘max-lisp-eval-depth’" appears.  Attached to this mail are the contents
of the backtrace buffer, and the contents of the *debug tramp/cache nil*
and *debug tramp/rclone memory* buffers.

I tried to debug the issue for myself for a while.  The first issue I
encountered, is that ‘tramp-rclone’ contains a call to
‘tramp-call-process’ with a DESTINATION of 0.  ‘tramp-call-process’
contains

  (tramp-get-buffer-string destination)

which in that case yields an error.  I tried changing "destination" in
that line into:

  (unless (eq destination 0) destination)

But then other problems occur.

Output of rclone --version:

  rclone v1.62.2
  - os/version: arch (64 bit)
  - os/kernel: 6.3.9-arch1-1 (x86_64)
  - os/type: linux
  - os/arch: amd64
  - go/version: go1.20.4
  - go/linking: dynamic
  - go/tags: none

In GNU Emacs 29.0.92 (build 2, x86_64-pc-linux-gnu, GTK+ Version
 3.24.38, cairo version 1.17.8) of 2023-06-25 built on huette
Repository revision: d0147ff9e507cc4e99e0574eab106f95c8e9df1f
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Arch Linux

Configured using:
 'configure --with-x-toolkit=gtk --with-native-compilation=yes
 --with-tree-sitter --with-json --with-mailutils --with-imagemagick'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
IMAGEMAGICK JPEG JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3
THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2
XPM GTK3 ZLIB

Important settings:
  value of $LC_COLLATE: C
  value of $LANG: C.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Outline

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec epa derived epg rfc6068 epg-config
gnus-util text-property-search mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils cl-extra debug help-fns
radix-tree cl-print backtrace help-mode find-func tramp-cache noutline
outline icons time-stamp tramp-rclone tramp-fuse tramp tramp-loaddefs
trampver tramp-integration files-x tramp-compat rx shell pcomplete
comint ansi-osc ansi-color ring parse-time iso8601 time-date format-spec
auth-source cl-seq eieio eieio-core cl-macs cl-loaddefs cl-lib
password-cache json subr-x map byte-opt gv bytecomp byte-compile rmc
iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting cairo move-toolbar gtk x-toolkit xinput2 x multi-tty
make-network-process native-compile emacs)

Memory information:
((conses 16 236774 13267)
 (symbols 48 10472 0)
 (strings 32 29017 1828)
 (string-bytes 1 931634)
 (vectors 16 22627)
 (vector-slots 8 718681 79929)
 (floats 8 42 131)
 (intervals 56 23110 0)
 (buffers 984 15))

backtrace.xz
Description: application/xz

debug-tramp-cache-nil.xz
Description: application/xz

debug-tramp-rclone-memory.xz
Description: application/xz