Keeping a tidy .emacs.d/ with no-littering.el

No-littering.el keeps your .emacs.d clean. I’ve been using it for years—in fact it’s one of the only third-party packages I first installed several years ago when I started using Emacs that I still have in my config today.

It establishes conventions for keeping files created from packages:

1. The no-littering-etc-directory. The directory where packages place their configuration files.
2. The no-littering-var-directory. The directory where packages place their persistent data files.

If every package followed this convention, then no files should litter (pun intended) your emacs configuration directory. Unfortunately, not every package does… fortunately, no-littering already sets the relevant option of dozens of packages to use these directories. But if you use a package that isn’t already set, you can easily use no-littering-expand-var-file-name and no-littering-expand-etc-file-name to change that. For example: (setopt cursory-latest-state-file (no-littering-expand-var-file-name "cursory/cursory-latest-state")) sets cursory-latest-state-file to ~/.emacs.d/var/cursory/cursory-latest-state.

Here’s a look at my own directories.

1. My no-littering-etc-directory, located at ~/.emacs.d/etc/:

   $ tree -L 1
   .
   ├── abbrev.el
   ├── custom.el
   ├── gnus
   └── transient
   
   3 directories, 2 files

2. My no-littering-var-directory, located at ~/.emacs.d/var/:

   $ tree -L 1
   .
   ├── abbrev-mode
   ├── amx-save.el
   ├── anaconda-mode
   ├── annotations.el
   ├── auto-save
   ├── backup
   ├── bookmark-default.el
   ├── citre
   ├── company
   ├── cursory
   ├── dap
   ├── dape-adapters
   ├── desktop
   ├── devdocs
   ├── diary
   ├── eaf
   ├── eafpdf
   ├── eglot-java
   ├── elfeed
   ├── emacs-gc-stats.eld.gz
   ├── emms
   ├── emojify
   ├── erc
   ├── eshell
   ├── eww
   ├── flycheck
   ├── fontaine
   ├── fontaine-latest-state.eld
   ├── forge
   ├── gamegrid-user-score
   ├── gdb-bp-session
   ├── .gitignore
   ├── .gitmodules
   ├── gnus
   ├── helm
   ├── ielm-history.eld
   ├── image-dired
   ├── irony
   ├── ispell
   ├── keyfreq.el
   ├── languagetool
   ├── ledger
   ├── logview-cache
   ├── lsp
   ├── mc-list.el
   ├── multisession
   ├── newsticker
   ├── nov-save-place.el
   ├── nsm-settings.el
   ├── org
   ├── org-remark
   ├── persist
   ├── popweb
   ├── prescient-save.el
   ├── projectile
   ├── project-list.el
   ├── project-x
   ├── psession
   ├── racket-mode
   ├── recentf-save.el
   ├── request
   ├── savehist.el
   ├── save-place.el
   ├── semantic
   ├── shadow
   ├── speed-type
   ├── spell-fu
   ├── srecode-map.el
   ├── svg-lib
   ├── tempel-templates
   ├── tramp
   ├── transient
   ├── trash
   ├── treemacs
   ├── treesit
   ├── tree-sitter
   ├── type-break.el
   ├── undohist
   ├── url
   ├── vimish-fold
   └── wombag
   
   60 directories, 22 files

Without no-littering, I would either (i) have a ton of directories in my .emacs.d or (ii) have to define my own variables whose values are directories and manually, whenever I install a new package, set their options to write their files into these directories—basically what no-littering already does but without no-littering’s existing integrations. This way, my Emacs directory is neater.

Bonus: (no-littering-theme-backups) §

No-littering also provides the little-known no-littering-theme-backups. The TL;DR is this: this function makes Emacs’s built-in auto-saving and backing up functions create files within no-littering’s directories so that sensitive data is not written to disk in unsecured locations. Calling this function sets the value of three variables:

1. auto-save-file-name-transforms: Transforms to apply to buffer file name before making auto-save file name.
2. backup-directory-alist: Similar to auto-save-file-name-transforms but for backup files.
3. undo-tree-history-directory-alist (from undo-tree): Similar to auto-save-file-name-transforms but for backup files.

Its docstring elaborates the mechanism and purpose of this function in greater depth:

no-littering-theme-backups is an autoloaded native-comp-function in
no-littering.el.

(no-littering-theme-backups)

Theme locations where backups of various sorts are created.

The purpose of this package is to store data files of various
sorts in a handful of central locations, instead of spreading
them all over the place.  When doing that for temporary files,
which contain backups of some sort, that increases the odds that
sensitive data is written to disk in clear text and/or that such
clear text files persist longer, if they would be created anyway.

Because of that, simply loading ‘no-littering’ does not theme
certain, potentially unsafe variables.  Instead, this function is
provided, so that you can decide whether to take the risk or not.

Calling this function sets these variables:
- auto-save-file-name-transforms (built-in)
- backup-directory-alist (built-in)
- undo-tree-history-directory-alist (from ‘undo-tree’)

The default values of these variables cause additional files to
be created in the same directories as the files that are being
visited.  Calling this function changes the values of these
variables, so that this is only done for visited files located in
certain directories.  For all other visited files, the additional
files are created in files inside no-littering-var-directory.

Additional files are created in the same directory as the visited
file, for files located in:
- "/tmp/"
- "/dev/shm"
- temporary-file-directory

With these settings it is still possible that sensitive data is
written to additional files, but you are more likely to spot it,
and because these directories usually use a ‘tmpfs’ file-system,
the leaked secrets should not persist after a reboot.

If you do *not* call this function, then these additional files
are always created in the same directory as the visited files,
regardless of the location of the visited files.  In other words,
even when using the default values, there is a significant risk
of leaking sensitive data, and if you want to reduce that, then
you must turn of these features completely.