bug#74385: [PATCH 1/4] srfi-64: Fix maybe-print-prop.

[Tomas Volf <~@wolfsden.cz>]

Previously it always printed the property, regardless of whether it was set or
not.

* module/srfi/srfi-64.scm (test-on-test-end-simple)[maybe-print-prop]:
Print only set properties.
---
 module/srfi/srfi-64.scm | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/module/srfi/srfi-64.scm b/module/srfi/srfi-64.scm
index 98fcef645..13ae26d48 100644
--- a/module/srfi/srfi-64.scm
+++ b/module/srfi/srfi-64.scm
@@ -418,15 +418,16 @@ instead."
 (define (test-on-test-end-simple runner)
   "Log that test is done."
   (define (maybe-print-prop prop pretty?)
-    (let* ((val (test-result-ref runner prop))
-           (val (string-trim-both
-                 (with-output-to-string
-                   (λ ()
-                     (if pretty?
-                         (pretty-print val #:per-line-prefix "             ")
-                         (display val)))))))
-      (when val
-        (format #t "~a: ~a~%" prop val))))
+    (let* ((default (list))
+           (val (test-result-ref runner prop default)))
+      (unless (eq? val default)
+        (let ((val (string-trim-both
+                    (with-output-to-string
+                      (λ ()
+                        (if pretty?
+                            (pretty-print val #:per-line-prefix "             ")
+                            (display val)))))))
+          (format #t "~a: ~a~%" prop val)))))
 
   (let ((result-kind (test-result-kind runner)))
     ;; Skip tests not executed due to run list.
-- 
2.46.0