gnu: home: dotfiles: Properly support both plain and Stow directory layouts.

Fixes <https://issues.guix.gnu.org/68848>.

The current implementation of the home-dotfiles-service-type contradicts
the Guix manual.  This patch properly implements both the plain and Stow
dotfiles directory layouts.

It does so by refactoring home-dotfiles-configuration adding a new
packages field to support GNU Stow's users workflow and introducing
a new layout field to switch between the two directory layouts.

* gnu/home/services/dotfiles (home-dotfiles-configuration): Migrate to
(gnu services configuration);
[packages]: new field;
[layout]: new field;
(strip-stow-dotfile): new variable;
(strip-plain-dotfile): new variable;
(home-dotfiles-configuration->files): use the new fields;
[directory-contents]: allow for
selecting a subset of application dotfile directories;
* doc/guix.texi: document the new layouts.

Change-Id: I2e96037608353e360828290f055ec5271cfdfd48
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 151 insertions, 48 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 176c92971fc..858d5751bfe 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -111,7 +111,7 @@ Copyright @copyright{} 2022 (@*
 Copyright @copyright{} 2022 John Kehayias@*
 Copyright @copyright{} 2022⁠–⁠2023 Bruno Victal@*
 Copyright @copyright{} 2022 Ivan Vilata-i-Balaguer@*
-Copyright @copyright{} 2023 Giacomo Leidi@*
+Copyright @copyright{} 2023-2024 Giacomo Leidi@*
 Copyright @copyright{} 2022 Antero Mejr@*
 Copyright @copyright{} 2023 Karl Hallsby@*
 Copyright @copyright{} 2023 Nathaniel Nicandro@*
@@ -44667,17 +44667,42 @@ directory, and some way of automatically deploy changes to their user home.
 @cindex Stow-like dot file management
 The @code{home-dotfiles-service-type} from @code{(gnu home services dotfiles)}
 is designed to ease the way into using Guix Home for this kind of users,
-allowing them to point the service to their dotfiles directory, which must
-follow the layout suggested by
-@uref{https://www.gnu.org/software/stow/, GNU Stow},
-and have their dotfiles automatically deployed to their user home, without
+allowing them to point the service to their dotfiles directory without
 migrating them to Guix native configurations.
 
-The dotfiles directory layout is expected to be structured as follows. Please
-keep in mind that it is advisable to keep your dotfiles directories under
+Please keep in mind that it is advisable to keep your dotfiles directories under
 version control, for example in the same repository where you'd track your
 Guix Home configuration.
 
+There are two supported dotfiles directory layouts, for now. The
+@code{'plain} layout, which is structured as follows:
+
+@example
+~$ tree -a ./dotfiles/
+dotfiles/
+├── .gitconfig
+├── .gnupg
+│   ├── gpg-agent.conf
+│   └── gpg.conf
+├── .guile
+├── .config
+│   ├── guix
+│   │   └── channels.scm
+│   └── nixpkgs
+│       └── config.nix
+├── .nix-channels
+├── .tmux.conf
+└── .vimrc
+@end example
+
+This tree structure is installed as is to the
+home directory upon @command{guix home reconfigure}.
+
+The @code{'stow} layout, which must
+follow the layout suggested by
+@uref{https://www.gnu.org/software/stow/, GNU Stow} presents an additional
+application specific directory layer, just like:
+
 @example
 ~$ tree -a ./dotfiles/
 dotfiles/
@@ -44707,8 +44732,10 @@ dotfiles/
 @end example
 
 For an informal specification please refer to the Stow manual
-(@pxref{Top,,, stow, Introduction}). A suitable configuration would then
-be:
+(@pxref{Top,,, stow, Introduction}). This tree structure is installed following
+GNU Stow's logic to the home directory upon @command{guix home reconfigure}.
+
+A suitable configuration with a @code{'plain} layout could be:
 
 @lisp
 (home-environment
@@ -44716,7 +44743,7 @@ be:
   (services
     (service home-dotfiles-service-type
              (home-dotfiles-configuration
-               (directories (list "./dotfiles"))))))
+               (directories '("./dotfiles"))))))
 @end lisp
 
 The expected home directory state would then be:
@@ -44743,32 +44770,47 @@ Return a service which is very similiar to @code{home-files-service-type}
 (and actually extends it), but designed to ease the way into using Guix
 Home for users that already track their dotfiles under some kind of version
 control.  This service allows users to point Guix Home to their dotfiles
-directory and have their files automatically deployed to their home directory
-just like Stow would, without migrating all of their dotfiles to Guix native
+directory and have their files automatically provisioned to their home
+directory, without migrating all of their dotfiles to Guix native
 configurations.
 @end defvar
 
+@c %start of fragment
+
 @deftp {Data Type} home-dotfiles-configuration
 Available @code{home-dotfiles-configuration} fields are:
 
 @table @asis
-@item @code{source-directory} (default: @code{(current-source-directory)})
-The path where dotfile directories are resolved. By default dotfile directories
-are resolved relative the source location where
+@item @code{source-directory} (default: @code{(current-source-directory)}) (type: string)
+The path where dotfile directories are resolved.  By default dotfile
+directories are resolved relative the source location where
 @code{home-dotfiles-configuration} appears.
 
-@item @code{directories} (type: list-of-strings)
-The list of dotfiles directories where @code{home-dotfiles-service-type} will
-look for application dotfiles.
+@item @code{layout} (default: @code{'plain}) (type: symbol)
+The intended layout of the specified @code{directory}.  It can be either
+@code{'stow} or @code{'plain}.
+
+@item @code{directories} (default: @code{'()}) (type: list-of-strings)
+The list of dotfiles directories where @code{home-dotfiles-service-type}
+will look for application dotfiles.
+
+@item @code{packages} (type: maybe-list-of-strings)
+The names of a subset of the GNU Stow package layer directories.  When provided
+the @code{home-dotfiles-service-type} will only provision dotfiles from this
+subset of applications.  This field will be ignored if @code{layout} is set
+to @code{'plain}.
 
-@item @code{exclude} (default: @code{'(".*~" ".*\\.swp" "\\.git" "\\.gitignore")})
-The list of file patterns @code{home-dotfiles-service-type} will exclude while
-visiting each one of the @code{directories}.
+@item @code{excluded} (default: @code{'(".*~" ".*\\.swp" "\\.git" "\\.gitignore")}) (type: list-of-strings)
+The list of file patterns @code{home-dotfiles-service-type} will exclude
+while visiting each one of the @code{directories}.
 
 @end table
 
 @end deftp
 
+
+@c %end of fragment
+
 @defvar home-xdg-configuration-files-service-type
 The service is very similar to @code{home-files-service-type} (and
 actually extends it), but used for defining files, which will go to
diff --git a/gnu/home/services/dotfiles.scm b/gnu/home/services/dotfiles.scm
index 6a740c42ce4..823bdb03fb4 100644
--- a/gnu/home/services/dotfiles.scm
+++ b/gnu/home/services/dotfiles.scm
@@ -20,17 +20,25 @@
 (define-module (gnu home services dotfiles)
   #:use-module (gnu home services)
   #:use-module (gnu services)
+  #:use-module (gnu services configuration)
   #:autoload   (guix build utils) (find-files)
+  #:use-module (guix diagnostics)
   #:use-module (guix gexp)
-  #:use-module (guix records)
+  #:use-module (guix i18n)
   #:use-module ((guix utils) #:select (current-source-directory))
   #:use-module (srfi srfi-1)
   #:use-module (ice-9 ftw)
+  #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
   #:export (home-dotfiles-service-type
+            home-dotfiles-configuration->files
+
             home-dotfiles-configuration
             home-dotfiles-configuration?
+            home-dotfiles-configuration-fields
+            home-dotfiles-configuration-layout
             home-dotfiles-configuration-source-directory
+            home-dotfiles-configuration-packages
             home-dotfiles-configuration-directories
             home-dotfiles-configuration-excluded))
 
@@ -40,26 +48,64 @@
     "\\.git"
     "\\.gitignore"))
 
-(define-record-type* <home-dotfiles-configuration>
-  home-dotfiles-configuration make-home-dotfiles-configuration
-  home-dotfiles-configuration?
-  (source-directory  home-dotfiles-configuration-source-directory
-                     (default (current-source-directory))
-                     (innate))
-  (directories       home-dotfiles-configuration-directories       ;list of strings
-                     (default '()))
-  (excluded          home-dotfiles-configuration-excluded       ;list of strings
-                     (default %home-dotfiles-excluded)))
-
-(define (import-dotfiles directory files)
+(define %home-dotfiles-layouts
+  '(plain stow))
+
+(define (sanitize-layout value)
+  (if (member value %home-dotfiles-layouts)
+      value
+      (raise
+       (formatted-message
+        (G_ "layout field of home-dotfiles-configuration should be either 'plain
+or 'stow, but ~a was found.")
+        value))))
+
+(define list-of-strings?
+  (list-of string?))
+
+(define-maybe list-of-strings)
+
+(define-configuration/no-serialization home-dotfiles-configuration
+  (source-directory
+   (string (current-source-directory))
+   "The path where dotfile directories are resolved.  By default dotfile
+directories are resolved relative the source location where
+@code{home-dotfiles-configuration} appears.")
+  (layout
+   (symbol 'plain)
+   "The intended layout of the specified @code{directory}.  It can be either
+@code{'stow} or @code{'plain}."
+   (sanitizer sanitize-layout))
+  (directories
+   (list-of-strings '())
+   "The list of dotfiles directories where @code{home-dotfiles-service-type}
+will look for application dotfiles.")
+  (packages
+   (maybe-list-of-strings)
+   "The names of a subset of the GNU Stow package layer directories.  When provided
+the @code{home-dotfiles-service-type} will only provision dotfiles from this
+subset of applications.  This field will be ignored if @code{layout} is set
+to @code{'plain}.")
+  (excluded
+   (list-of-strings %home-dotfiles-excluded)
+   "The list of file patterns @code{home-dotfiles-service-type} will exclude
+while visiting @code{directory}."))
+
+(define (strip-stow-dotfile file-name directory)
+  (let ((dotfile-name (string-drop file-name (1+ (string-length directory)))))
+    (match (string-split dotfile-name #\/)
+      ((package parts ...)
+       (string-join parts "/")))))
+
+(define (strip-plain-dotfile file-name directory)
+  (string-drop file-name (+ 1 (string-length directory))))
+
+(define (import-dotfiles directory files strip)
   "Return a list of objects compatible with @code{home-files-service-type}'s
 value.  Each object is a pair where the first element is the relative path
 of a file and the second is a gexp representing the file content.  Objects are
 generated by recursively visiting DIRECTORY and mapping its contents to the
 user's home directory, excluding files that match any of the patterns in EXCLUDED."
-  (define (strip file)
-    (string-drop file (+ 1 (string-length directory))))
-
   (define (format file)
     ;; Remove from FILE characters that cannot be used in the store.
     (string-append
@@ -73,7 +119,7 @@ user's home directory, excluding files that match any of the patterns in EXCLUDE
                  file)))
 
   (map (lambda (file)
-         (let ((stripped (strip file)))
+         (let ((stripped (strip file directory)))
            (list stripped
                  (local-file file (format stripped)
                              #:recursive? #t))))
@@ -81,18 +127,25 @@ user's home directory, excluding files that match any of the patterns in EXCLUDE
 
 (define (home-dotfiles-configuration->files config)
   "Return a list of objects compatible with @code{home-files-service-type}'s
-value, generated following GNU Stow's algorithm for each of the
-directories in CONFIG, excluding files that match any of the patterns configured."
+value, excluding files that match any of the patterns configured."
+  (define stow? (eq? (home-dotfiles-configuration-layout config) 'stow))
   (define excluded
     (home-dotfiles-configuration-excluded config))
   (define exclusion-rx
     (make-regexp (string-append "^.*(" (string-join excluded "|") ")$")))
 
-  (define (directory-contents directory)
-    (find-files directory
-                (lambda (file stat)
-                  (not (regexp-exec exclusion-rx
-                                    (basename file))))))
+  (define* (directory-contents directory #:key (packages #f))
+    (define (filter-files directory)
+      (find-files directory
+                  (lambda (file stat)
+                    (not (regexp-exec exclusion-rx
+                                      (basename file))))))
+    (if (and stow? packages (maybe-value-set? packages))
+        (append-map filter-files
+                    (map (lambda (pkg)
+                           (string-append directory "/" pkg))
+                         packages))
+        (filter-files directory)))
 
   (define (resolve directory)
     ;; Resolve DIRECTORY relative to the 'source-directory' field of CONFIG.
@@ -103,15 +156,23 @@ directories in CONFIG, excluding files that match any of the patterns configured
 
   (append-map (lambda (directory)
                 (let* ((directory (resolve directory))
-                       (contents  (directory-contents directory)))
-                  (import-dotfiles directory contents)))
+                       (packages
+                        (home-dotfiles-configuration-packages config))
+                       (contents
+                        (directory-contents directory
+                                            #:packages packages))
+                       (strip
+                        (if stow? strip-stow-dotfile strip-plain-dotfile)))
+                  (import-dotfiles directory contents strip)))
               (home-dotfiles-configuration-directories config)))
 
 (define-public home-dotfiles-service-type
   (service-type (name 'home-dotfiles)
                 (extensions
                  (list (service-extension home-files-service-type
-                                          home-dotfiles-configuration->files)))
+                                          (lambda (config)
+                                            (when config
+                                              (home-dotfiles-configuration->files config))))))
                 (default-value (home-dotfiles-configuration))
                 (description "Files that will be put in the user's home directory
 following GNU Stow's algorithm, and further processed during activation.")))