diff mbox series

[bug#72867,v3] gexp: Make 'local-file' follow symlinks.

Message ID 2d4b593eaea4fed1fb08031a599aaab032442041.1725263612.git.nigko.yerden@gmail.com
State New
Headers show
Series [bug#72867,v3] gexp: Make 'local-file' follow symlinks. | expand

Commit Message

Nigko Yerden Sept. 2, 2024, 7:53 a.m. UTC
Fixes <https://lists.gnu.org/archive/html/guix-devel/2024-08/msg00047.html>

While the issue can be easily fixed (a one line change in 'absolute-dirname')
by changing 'current-source-directory' so that it always follows symlinks,
such a change may break someone else's code. Instead, this patch keeps the
original behavior of 'current-source-directory' macro and adds optional
'follow-symlinks?' argument to it.

This patch is the result of collective work of
Florian Pelz <pelzflorian@pelzflorian.de> and
Nigko Yerden <nigko.yerden@gmail.com>

* guix/utils.scm (absolute-dirname): Add 'follow-symlinks?' mandatory
argument.
(%guix-source-root-directory): Pass #f to 'absolute-dirname'
'follow-symlinks?' argument.
(current-source-directory): Add 'follow-symlinks?' optional argument.
* guix/gexp.scm (local-file): Pass #t to 'current-source-directory'
'follow-symlinks?' argument.
* tests/gexp.scm ("local-file, load through symlink"): New test.

Change-Id: Ieb30101275deb56b7436df444f9bc21d240fba59
---
Forgot to unwrap #'follow-symlinks? syntax object with 'syntax->datum'
when calling 'source-directory' inside 'current-source-directory'.

 guix/gexp.scm  |  2 +-
 guix/utils.scm | 53 ++++++++++++++++++++++++++++----------------------
 tests/gexp.scm | 23 ++++++++++++++++++++++
 3 files changed, 54 insertions(+), 24 deletions(-)


base-commit: 4c49cd171e2aa06af05cf52403050b18f100867a

Comments

pelzflorian (Florian Pelz) Sept. 3, 2024, 3:05 p.m. UTC | #1
Hello Nigko.

Nigko Yerden <nigko.yerden@gmail.com> writes:
> This patch is the result of collective work of
> Florian Pelz <pelzflorian@pelzflorian.de> and
> Nigko Yerden <nigko.yerden@gmail.com>

Thanks for the credit, but it would be unusual to mention me in the
commit message, where discussion does not count.

Please do not put me in the commit message; I made no code contribution.

I also would favor to simplify `current-source-directory' and not add an
optional follow-symlinks? argument.  I believe processing profiles is
the only reasonable case that unconditionally following symlinks would
break, and people do not do profile processing in outside code.

> * tests/gexp.scm ("local-file, load through symlink"): New test.

This one is a good test; but it tests only half, namely the
rare-in-practice case of `local-file' when loading a Scheme file.  Here,
`current-source-directory' evaluate file-name to
"/tmp/guix-directory.VxrxZT/dir/link-to-code.scm", which has a slash as
prefix, so absolute-dirname is not called.

The original issue is that the package in a channel according to
cookbook’s “The Repository as a Channel” cannot be built when the
load-path is set up in the usual way.  There, absolute-dirname gets
called.  I think we would need a (very similar) test that covers this.

Instead of primitive-load, we would need to invoke Guile on a file in a
channel or in the GUILE_LOAD_PATH, or set %load-path.  I may be wrong
here and do not know how, but we definitely should cover when
`file-name' in is not prefixed with a slash.

Regards,
Florian
Nigko Yerden Sept. 5, 2024, 5:06 a.m. UTC | #2
Hello Florian,

pelzflorian (Florian Pelz) wrote:
> I also would favor to simplify `current-source-directory' and not add an
> optional follow-symlinks? argument.  I believe processing profiles is
> the only reasonable case that unconditionally following symlinks would
> break, and people do not do profile processing in outside code.
Why do you think that making 'current-source-directory' to always follow
symlinks would not break Guix's own code as well?

What are these people whose code would be broken supposed to do? I think
they would need to write their own 'current-source-directory' from scratch.
Why not help them by providing 'follow-symlinks?' argument?

Instead of 'current-source-directory' simplification we can also consider
changing the default for 'follow-symlinks?' to #t.

Regards,
Nigko
diff mbox series

Patch

diff --git a/guix/gexp.scm b/guix/gexp.scm
index 74b4c49f90..5911ca4815 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -508,7 +508,7 @@  (define-syntax local-file
        (string? (syntax->datum #'file))
        ;; FILE is a literal, so resolve it relative to the source directory.
        #'(%local-file file
-                      (delay (absolute-file-name file (current-source-directory)))
+                      (delay (absolute-file-name file (current-source-directory #t)))
                       rest ...))
       ((_ (assume-valid-file-name file) rest ...)
        ;; FILE is not a literal, so resolve it relative to the current
diff --git a/guix/utils.scm b/guix/utils.scm
index d8ce6ed886..ea3d80707e 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -1110,41 +1110,48 @@  (define (canonical-newline-port port)
 
 (define (%guix-source-root-directory)
   "Return the source root directory of the Guix found in %load-path."
-  (dirname (absolute-dirname "guix/packages.scm")))
+  (dirname (absolute-dirname "guix/packages.scm" #f)))
 
 (define absolute-dirname
   ;; Memoize to avoid repeated 'stat' storms from 'search-path'.
-  (mlambda (file)
+  (mlambda (file follow-symlinks?)
     "Return the absolute name of the directory containing FILE, or #f upon
-failure."
+failure. Follow symlinks if FOLLOW-SYMLINKS? is true."
     (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)))))))
+       (if follow-symlinks?
+	   (dirname (canonicalize-path 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))))))))
 
 (define-syntax current-source-directory
   (lambda (s)
     "Return the absolute name of the current directory, or #f if it could not
-be determined."
+be determined. Do not follow symlinks if FOLLOW-SYMLINKS? is false (the default)."
+    (define (source-directory follow-symlinks?)
+      (match (assq 'filename (or (syntax-source s) '()))
+	(('filename . (? string? file-name))
+	 ;; If %FILE-PORT-NAME-CANONICALIZATION is 'relative, then FILE-NAME
+	 ;; can be relative.  In that case, we try to find out at run time
+	 ;; the absolute file name by looking at %LOAD-PATH; doing this at
+	 ;; run time rather than expansion time is necessary to allow files
+	 ;; to be moved on the file system.
+	 (if (string-prefix? "/" file-name)
+	     (dirname (if follow-symlinks?
+			  (canonicalize-path file-name)
+			  file-name))
+	     #`(absolute-dirname #,file-name #,follow-symlinks?)))
+	((or ('filename . #f) #f)
+	 ;; raising an error would upset Geiser users
+	 #f)))
     (syntax-case s ()
-      ((_)
-       (match (assq 'filename (or (syntax-source s) '()))
-         (('filename . (? string? file-name))
-          ;; If %FILE-PORT-NAME-CANONICALIZATION is 'relative, then FILE-NAME
-          ;; can be relative.  In that case, we try to find out at run time
-          ;; the absolute file name by looking at %LOAD-PATH; doing this at
-          ;; 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)
-              #`(absolute-dirname #,file-name)))
-         ((or ('filename . #f) #f)
-          ;; raising an error would upset Geiser users
-          #f))))))
+      ((_) (source-directory #f))
+      ((_ follow-symlinks?)
+       (source-directory (syntax->datum #'follow-symlinks?))))))
 
 
 ;;;
diff --git a/tests/gexp.scm b/tests/gexp.scm
index b35bfc920f..843037fa84 100644
--- a/tests/gexp.scm
+++ b/tests/gexp.scm
@@ -292,6 +292,29 @@  (define %extension-package
                  (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 code 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 "code.scm"
+       (lambda (port) (display "\
+(use-modules (guix gexp))
+(define file (local-file \"content\" \"test-file\"))
+(local-file-absolute-file-name file)" port)))
+     (mkdir "dir")
+     (chdir "dir")
+     (symlink "../code.scm" "link-to-code.scm")
+     ;; call 'local-file' through symlink
+     (primitive-load (string-append tmp-dir "/dir/link-to-code.scm")))))
+
 (test-assert "one plain file"
   (let* ((file     (plain-file "hi" "Hello, world!"))
          (exp      (gexp (display (ungexp file))))