gexp: Make 'local-file' follow symlinks.issue-72867

Fix <https://lists.gnu.org/archive/html/guix-devel/2024-08/msg00047.html>
via making 'current-source-directory' always follow symlinks.

* guix/utils.scm (absolute-dirname, current-source-directory): Make
them follow symlinks.
* tests/gexp.scm ("local-file, load through symlink"): New test.

Change-Id: Ieb30101275deb56b7436df444f9bc21d240fba59

2 files changed, 35 insertions, 6 deletions

diff --git a/guix/utils.scm b/guix/utils.scm
index f161cb4ef3..d4591caced 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -1121,11 +1121,7 @@ failure."
     (match (search-path %load-path file)
       (#f #f)
       ((? string? file)
-       ;; If there are relative names in %LOAD-PATH, FILE can be relative and
-       ;; needs to be canonicalized.
-       (if (string-prefix? "/" file)
-           (dirname file)
-           (canonicalize-path (dirname file)))))))
+       (dirname (canonicalize-path file))))))
 
 (define-syntax current-source-directory
   (lambda (s)
@@ -1141,7 +1137,7 @@ be determined."
           ;; run time rather than expansion time is necessary to allow files
           ;; to be moved on the file system.
           (if (string-prefix? "/" file-name)
-              (dirname file-name)
+              (dirname (canonicalize-path file-name))
               #`(absolute-dirname #,file-name)))
          ((or ('filename . #f) #f)
           ;; raising an error would upset Geiser users
diff --git a/tests/gexp.scm b/tests/gexp.scm
index e066076c5c..cd502a1fb2 100644
--- a/tests/gexp.scm
+++ b/tests/gexp.scm
@@ -298,6 +298,39 @@
                  (equal? (scandir (string-append dir "/tests"))
                          '("." ".." "gexp.scm"))))))
 
+(test-assert "local-file, load through symlink"
+  ;; See <https://issues.guix.gnu.org/72867>.
+  (call-with-temporary-directory
+   (lambda (tmp-dir)
+     (chdir tmp-dir)
+     ;; create content file
+     (call-with-output-file "content"
+       (lambda (port) (display "Hi!" port)))
+     ;; Create module that call 'local-file'
+     ;; with the content file and returns its
+     ;; absolute file-name. An error is raised
+     ;; if the content file can't be found.
+     (call-with-output-file "test-local-file.scm"
+       (lambda (port) (display "\
+(define-module (test-local-file)
+  #:use-module (guix gexp))
+(define file (local-file \"content\" \"test-file\"))
+(local-file-absolute-file-name file)" port)))
+     (mkdir "dir")
+     (chdir "dir")
+     (symlink "../test-local-file.scm" "test-local-file.scm")
+     ;; 'local-file' in turn calls 'current-source-directory'
+     ;; which has an 'if' branching condition depending on whether
+     ;; 'file-name' is absolute or relative path. To test both
+     ;; of these branches we execute 'test-local-file.scm' symlink
+     ;; first as a module (corresponds to relative path):
+     (dynamic-wind
+       (lambda () (set! %load-path (cons "." %load-path)))
+       (lambda () (use-modules (test-local-file)))
+       (lambda () (set! %load-path (cdr %load-path))))
+     ;; and then as a regular code (corresponds to absolute path):
+     (load (string-append tmp-dir "/dir/test-local-file.scm")))))
+
 (test-assert "one plain file"
   (let* ((file     (plain-file "hi" "Hello, world!"))
          (exp      (gexp (display (ungexp file))))