[bug#70829] [PATCH v4] guix: gexp: Add assume-source-relative-file-name

[Richard Sent]

guix/gexp.scm (assume-source-relative-file-name): Create syntax rule
(local-file): Use assume-source-relative-file-name to look up a non-literal
file relative to the current source directory.
doc/guix.texi (G-expressions): Document it.
tests: gexp.scm: Test it.
---
Hi all,

Since #70830 wound up being merged, I'm resubmitting this patch
rebased on master and without the documentation for
assume-valid-file-name.

 doc/guix.texi  |  5 +++++
 guix/gexp.scm  | 15 ++++++++++++++-
 tests/gexp.scm |  6 ++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 8cc01b2e65..d291da4b98 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -12204,6 +12204,11 @@ G-Expressions
 (local-file (assume-valid-file-name alice-key-file-path))
 @end lisp
 
+@var{file} can be wrapped in the @code{assume-source-relative-file-name}
+syntactic keyword.  When this is done, the file name will be looked up
+relative to the source file where it appears even when it is not a
+string literal.
+
 This is the declarative counterpart of the @code{interned-file} monadic
 procedure (@pxref{The Store Monad, @code{interned-file}}).
 @end deffn
diff --git a/guix/gexp.scm b/guix/gexp.scm
index 74b4c49f90..871e59cfdc 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -52,6 +52,7 @@ (define-module (guix gexp)
             gexp-input-native?
 
             assume-valid-file-name
+            assume-source-relative-file-name
             local-file
             local-file?
             local-file-file
@@ -485,6 +486,12 @@ (define-syntax-rule (assume-valid-file-name file)
 warn about it."
   file)
 
+(define-syntax-rule (assume-source-relative-file-name file)
+  "This is a syntactic keyword to tell 'local-file' that it can assume that
+the given file is relative to the source directory, even if it's not a string
+literal."
+  file)
+
 (define-syntax local-file
   (lambda (s)
     "Return an object representing local file FILE to add to the store; this
@@ -503,13 +510,19 @@ (define-syntax local-file
 This is the declarative counterpart of the 'interned-file' monadic procedure.
 It is implemented as a macro to capture the current source directory where it
 appears."
-    (syntax-case s (assume-valid-file-name)
+    (syntax-case s (assume-valid-file-name assume-source-relative-file-name)
       ((_ file rest ...)
        (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)))
                       rest ...))
+      ((_ (assume-source-relative-file-name file) rest ...)
+       ;; FILE is not a literal, but the user requested we look it up
+       ;; relative to the current source directory.
+       #'(%local-file file
+                      (delay (absolute-file-name file 
(current-source-directory)))
+                      rest ...))
       ((_ (assume-valid-file-name file) rest ...)
        ;; FILE is not a literal, so resolve it relative to the current
        ;; directory.  Since the user declared FILE is valid, do not pass
diff --git a/tests/gexp.scm b/tests/gexp.scm
index 905009caee..8774097bd0 100644
--- a/tests/gexp.scm
+++ b/tests/gexp.scm
@@ -244,6 +244,12 @@ (define %extension-package
       (let ((file (local-file (string-copy "../base32.scm"))))
         (local-file-absolute-file-name file)))))
 
+(test-equal "local-file, non-literal source relative file name"
+  (current-filename)
+  (let ((file (local-file (assume-source-relative-file-name
+                           (string-append "gexp" ".scm")))))
+    (local-file-absolute-file-name file)))
+
 (test-assert "local-file, relative file name, within gexp"
   (let* ((file     (search-path %load-path "guix/base32.scm"))
          (interned (add-to-store %store "base32.scm" #f "sha256" file)))

base-commit: 2e53fa5346bf52f6d6d26e035bc905ebd410dabb
-- 
2.45.1