GNU bug report logs - #78378
[PATCH 0/2] home: services: Build "files" union allowing dangling symlinks.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Sergey Trofimov <sarg <at> sarg.org.ru>
To: guix-patches <at> gnu.org
Cc: Sergey Trofimov <sarg <at> sarg.org.ru>
Subject: [PATCH 0/2] home: services: Build "files" union allowing dangling
 symlinks.
Date: Sun, 11 May 2025 18:00:50 +0200

This patch enables guix home users to create arbitrary symlinks in their home
environment. I.e. a user having "/storage" directory (probably residing on
another disk partition) could symlink e.g. "~/.mail" from
"/storage/data/mail". 

Sergey Trofimov (2):
  gexp: Add symlink-to procedure.
  home: services: Build "files" union allowing dangling symlinks.

 doc/guix.texi         | 11 +++++++++++
 gnu/home/services.scm | 16 +++++++++++++++-
 guix/gexp.scm         |  5 +++++
 tests/guix-home.sh    |  8 +++++++-
 4 files changed, 38 insertions(+), 2 deletions(-)


base-commit: f6363db18636172f959e2709982bbe09b411c3d8
-- 
2.49.0

Message #8 received at 78378 <at> debbugs.gnu.org (full text, mbox):

From: Sergey Trofimov <sarg <at> sarg.org.ru>
To: 78378 <at> debbugs.gnu.org
Cc: Sergey Trofimov <sarg <at> sarg.org.ru>
Subject: [PATCH 1/2] gexp: Add symlink-to procedure.
Date: Sun, 11 May 2025 18:08:02 +0200

* guix/gexp.scm (symlink-to): New procedure.
* doc/guix.texi (G-Expressions): Document it.

Change-Id: I7c1ba3a29a4e5350cb4f196185b7171c4750b6b8
---
 doc/guix.texi | 11 +++++++++++
 guix/gexp.scm |  5 +++++
 2 files changed, 16 insertions(+)

diff --git a/doc/guix.texi b/doc/guix.texi
index cbc4dd0fc9..ebc8a5e5d3 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -12689,6 +12689,17 @@ G-Expressions
 This yields an @code{etc} directory containing these two files.
 @end deffn
 
+@deffn {Procedure} symlink-to target
+Return a @code{<computed-file>} that is a symbolic link to target.
+Note, that the target does not need to exist at the build time.  One of
+uses is to put arbitrary symlinks into user's home:
+
+@lisp
+(service home-files-service-type
+  `(("Sync" ,(symlink-to "/storage/Sync"))))
+@end lisp
+@end deffn
+
 @deffn {Procedure} directory-union name things
 Return a directory that is the union of @var{things}, where @var{things} is a list of
 file-like objects denoting directories.  For example:
diff --git a/guix/gexp.scm b/guix/gexp.scm
index 8dd746eee0..ef83c671ec 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -119,6 +119,7 @@ (define-module (guix gexp)
             file-union
             directory-union
             references-file
+            symlink-to
 
             imported-files
             imported-modules
@@ -2181,6 +2182,10 @@ (define* (file-union name files #:key guile)
                             files)))))
                  #:guile guile))
 
+(define (symlink-to target)
+  "Return an object that is a symlink to TARGET."
+  (computed-file "link" (gexp (symlink (ungexp target) (ungexp output)))))
+
 (define* (directory-union name things
                           #:key (copy? #f) (quiet? #f)
                           (resolve-collision 'resolve-collision/default))
-- 
2.49.0

Message #11 received at 78378 <at> debbugs.gnu.org (full text, mbox):

From: Sergey Trofimov <sarg <at> sarg.org.ru>
To: 78378 <at> debbugs.gnu.org
Cc: Sergey Trofimov <sarg <at> sarg.org.ru>
Subject: [PATCH 2/2] home: services: Build "files" union allowing dangling
 symlinks.
Date: Sun, 11 May 2025 18:08:03 +0200

* gnu/home/services.scm (files->files-directory): Build file union
without checking for existence of included items.

* tests/guix-home.sh: Verify symlinking files out of store works.

Change-Id: I94054003f4a6be944252ce7a397cf56f0b979554
---
 gnu/home/services.scm | 16 +++++++++++++++-
 tests/guix-home.sh    |  8 +++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/gnu/home/services.scm b/gnu/home/services.scm
index 2342dc5e07..55f9365922 100644
--- a/gnu/home/services.scm
+++ b/gnu/home/services.scm
@@ -343,7 +343,21 @@ (define (files->files-directory files)
   ;; leading to a build failure of "files.drv".
   (assert-no-duplicates files)
 
-  (file-union "files" files))
+  ;; Compute the file-union allowing dangling symlinks
+  ;; This enables creating symlinks to locations out of store
+  (computed-file
+   "files"
+   (with-imported-modules '((guix build utils))
+     #~(begin
+         (use-modules (guix build utils)
+                      (ice-9 match))
+         (mkdir #$output)
+         (chdir #$output)
+         (for-each (match-lambda
+                     ((target source)
+                      (mkdir-p (dirname target))
+                      (symlink source target)))
+                   '#$files)))))
 
 ;; Used by symlink-manager
 (define home-files-directory "files")
diff --git a/tests/guix-home.sh b/tests/guix-home.sh
index dbfe7dbd48..b8d90196f1 100644
--- a/tests/guix-home.sh
+++ b/tests/guix-home.sh
@@ -73,7 +73,9 @@ trap 'chmod -Rf +w "$test_directory"; rm -rf "$test_directory"' EXIT
                    (list `(".config/test.conf"
                            ,(plain-file
                              "tmp-file.txt"
-                             "the content of ~/.config/test.conf"))))
+                             "the content of ~/.config/test.conf"))
+
+                         `("symlink" ,(symlink-to "<test_directory>"))))
 
    (service home-bash-service-type
             (home-bash-configuration
@@ -104,6 +106,7 @@ trap 'chmod -Rf +w "$test_directory"; rm -rf "$test_directory"' EXIT
                        "# the content of bashrc-test-config.sh"))))))))
 EOF
 
+    sed -i "s,<test_directory>,$test_directory," home.scm
     echo -n "# dot-bashrc test file for guix home" > "dot-bashrc"
 
     # Check whether the graph commands work as expected.
@@ -126,6 +129,7 @@ EOF
 	guix home container home.scm -- cat '~/.config/test.conf' | \
 	    grep "the content of"
 	guix home container home.scm -- test -h '~/.bashrc'
+	guix home container home.scm -- test -h '~/symlink'
 	test "$(guix home container home.scm -- id -u)" = 1000
 	guix home container home.scm -- test -f '$HOME/sample/home.scm' && false
 	guix home container home.scm --expose="$PWD=$HOME/sample" -- \
@@ -153,6 +157,8 @@ EOF
     test -d "${HOME}/.guix-home"
     test -h "${HOME}/.bash_profile"
     test -h "${HOME}/.bashrc"
+    test -h "${HOME}/symlink"
+    test "$(readlink -f $HOME/symlink)" == "$test_directory"
     grep 'alias run="guix shell"' "$HOME/.bashrc"
     grep "alias path='echo \$PATH'" "$HOME/.bashrc"
     test "$(tail -n 2 "${HOME}/.bashrc")" == "\
-- 
2.49.0

Message #14 received at 78378 <at> debbugs.gnu.org (full text, mbox):

From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: Sergey Trofimov <sarg <at> sarg.org.ru>
Cc: Josselin Poiret <dev <at> jpoiret.xyz>, Tobias Geerinckx-Rice <me <at> tobias.gr>,
 Simon Tournier <zimon.toutoune <at> gmail.com>, Mathieu Othacehe <othacehe <at> gnu.org>,
 Ludovic Courtès <ludo <at> gnu.org>,
 Gabriel Wicki <gabriel <at> erlikon.ch>, 78378 <at> debbugs.gnu.org,
 Christopher Baines <guix <at> cbaines.net>
Subject: Re: [bug#78378] [PATCH 1/2] gexp: Add symlink-to procedure.
Date: Mon, 12 May 2025 16:49:08 +0900

Sergey Trofimov <sarg <at> sarg.org.ru> writes:

> * guix/gexp.scm (symlink-to): New procedure.
> * doc/guix.texi (G-Expressions): Document it.
>
> Change-Id: I7c1ba3a29a4e5350cb4f196185b7171c4750b6b8

Reviewed-by: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>

-- 
Thanks,
Maxim

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