From 6b30eb189e48e290136d6a838729cf2eb07ee82f Mon Sep 17 00:00:00 2001
From: Ludovic Courtès <ludo@gnu.org>
Date: Sat, 27 Nov 2021 22:10:38 +0100
Subject: gexp: 'file-append' correctly handles bases without an expander.

This fixes this use case:

  (file-append (let-system ...) ...)

* guix/gexp.scm (file-append-compiler): When BASE lacks an expander,
delegate to LOWERED.
* tests/gexp.scm ("let-system in file-append"): New test.
---
 guix/gexp.scm | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'guix')

diff --git a/guix/gexp.scm b/guix/gexp.scm
index 56b1bb4951..01dca902f7 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -685,7 +685,8 @@ (define-gexp-compiler file-append-compiler <file-append>
   expander => (lambda (obj lowered output)
                 (match obj
                   (($ <file-append> base suffix)
-                   (let* ((expand (lookup-expander base))
+                   (let* ((expand (or (lookup-expander base)
+                                      (lookup-expander lowered)))
                           (base   (expand base lowered output)))
                      (string-append base (string-concatenate suffix)))))))
 
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