01/04: .dir-locals.el: Prevent errors if .dir-locals.el isn't found.

[guix-commits]

civodul pushed a commit to branch version-1.2.0
in repository guix.

commit e385e5fc3c6839ad3d700b50f908df8f6b9f3ad8
Author: Christopher Lemmer Webber <cwebber@dustycloud.org>
AuthorDate: Mon Nov 16 13:04:38 2020 -0500

    .dir-locals.el: Prevent errors if .dir-locals.el isn't found.
    
    While this repo should presumably always have a .dir-locals.el
    by the nature of this file itself, it seems that this behavior "leaks".
    See added comment for more details on the fix to this strange bug,
    which is likely an upstream emacs or vc-mode issue.
    
    Thanks to Miguel Ángel Arruga Vivas and Maxim Cournoyer for helping
    investigate this problem.
    
    * .dir-locals.el: Don't error out if .dir-locals.el isn't found.
---
 .dir-locals.el | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/.dir-locals.el b/.dir-locals.el
index b1cb936..4599f06 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -17,17 +17,27 @@
      ;; Geiser
      ;; This allows automatically setting the `geiser-guile-load-path'
      ;; variable when using various Guix checkouts (e.g., via git worktrees).
-     (eval . (let* ((root-dir (expand-file-name
-                               (locate-dominating-file
-                                default-directory ".dir-locals.el")))
-                    ;; Workaround for bug https://issues.guix.gnu.org/43818.
-                    (root-dir* (directory-file-name root-dir)))
-               (unless (boundp 'geiser-guile-load-path)
-                 (defvar geiser-guile-load-path '()))
-               (make-local-variable 'geiser-guile-load-path)
-               (require 'cl-lib)
-               (cl-pushnew root-dir* geiser-guile-load-path
-                           :test #'string-equal)))))
+     (eval . (let ((root-dir-unexpanded (locate-dominating-file
+                                         default-directory ".dir-locals.el")))
+               ;; While Guix should in theory always have a .dir-locals.el
+               ;; (we are reading this file, after all) there seems to be a
+               ;; strange problem where this code "escapes" to some other 
buffers,
+               ;; at least vc-mode.  See:
+               ;;   
https://lists.gnu.org/archive/html/guix-devel/2020-11/msg00296.html
+               ;; (TODO: add/replace with upstream emacs bug link when 
reported)
+               ;; Hence the following "when", which might otherwise be 
unnecessary;
+               ;; it prevents causing an error when root-dir-unexpanded is nil.
+               (when root-dir-unexpanded
+                 (let* ((root-dir (expand-file-name root-dir-unexpanded))
+                        ;; Workaround for bug 
https://issues.guix.gnu.org/43818.
+                        (root-dir* (directory-file-name root-dir)))
+
+                   (unless (boundp 'geiser-guile-load-path)
+                     (defvar geiser-guile-load-path '()))
+                   (make-local-variable 'geiser-guile-load-path)
+                   (require 'cl-lib)
+                   (cl-pushnew root-dir* geiser-guile-load-path
+                               :test #'string-equal)))))))
 
  (c-mode          . ((c-file-style . "gnu")))
  (scheme-mode