Spacemacs can't create auto-save files when using tramp on Windows.

[batonius]

Description

Spacemacs can't create auto-save files in the cache directory when using tramp on Windows. dotspacemacs-auto-save-file-location is set to 'cache.

Reproduction guide 🪲

• Start Emacs on Windows via msys2.
• Open a file on a remote server with tramp.
• Edit the file.
• Wait for auto-save to kick in.

Observed behaviour: 👀 💔
No new auto-save files in .cache/dist or .cache/site directories, error message in the Messages buffer:

Auto-saving test.sh: Opening output file: Invalid argument, d:/msys64/home/user/.emacs.d/.cache/auto-save/dist/#!plinkx:188:!home!user!test.sh#

Expected behaviour: ❤️ 😄
Auto-saving working properly. I've looked in ~/.emacs.d/.cache/auto-save and found auto-save files created by the previous version of Spacemacs in the site subdir, their names being of form #_aplinkx_b188_b_ahome_auser_atest.sh#, so I guess the problem is broken file name escaping.

System Info 💻

• OS: windows-nt
• Emacs: 25.1.1
• Spacemacs: 0.200.0
• Spacemacs branch: master (rev. e6357a5)
• Graphic display: t
• Distribution: spacemacs
• Editing style: vim
• Completion: helm
• Layers:

(helm emacs-lisp dockerfile
      (shell :variables shell-default-height 30 shell-default-shell 'shell shell-default-position 'bottom)
      rust markdown c-c  
      (colors :variables colors-colorize-identifiers 'all)
      sql php html)

[TheBB]

If Spacemacs caused this to happen it should be possible to bisect this. If not, you should probably report this upstream to the relevant places, since I don't think (famous last words) we are doing anything that might affect this.

[batonius]

You're right, the problem is with vanilla emacs 25.1.

I've looked into it and it looks like tramp has two methods for auto-save file name escaping: if tramp-auto-save-directory is set it uses it's own transformations (/ -> _a, : -> _b, etc) and if it's nil it uses the default behavior for the system provided by make-auto-save-file-name. The problem is, after this commit make-auto-save-file-name can't detect the system as windows-nt and fails to replace the forbidden symbols in file names. I don't understand the reasoning behind the commit, but I got auto-saving working by explicitly setting tramp-auto-save-directory:

 (setq tramp-auto-save-directory (concat spacemacs-auto-save-directory "tramp/"))

I'm aware this isn't your bug, but maybe Spacemacs could set tramp-auto-save-directory when it sets auto-save-file-name-transforms? It seems reasonable and would solve the problem.

[hieudang9]

Same here, but in babun shell, Windows 10, hang up in this phase:
Wrote /home/dt/.emacs.d/.cache/layouts/persp-auto-save

[github-actions]

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