store: Attempt to decode build logs as UTF-8.

* guix/serialization.scm (read-maybe-utf8-string): New procedure.
* guix/store.scm (process-stderr): Use it for the build log and errors.
* tests/store.scm ("current-build-output-port, UTF-8",
  "current-build-output-port, UTF-8 + garbage"): New tests.

1 files changed, 6 insertions, 3 deletions

diff --git a/guix/store.scm b/guix/store.scm
index d88fb3ea54..a3f3cbf43b 100644
--- a/guix/store.scm
+++ b/guix/store.scm
@@ -418,15 +418,18 @@ encoding conversion errors."
              (write-padding len p)
              #f))
           ((= k %stderr-next)
-           ;; Log a string.
-           (let ((s (read-latin1-string p)))
+           ;; Log a string.  Build logs are usually UTF-8-encoded, but they
+           ;; may also contain arbitrary byte sequences that should not cause
+           ;; this to fail.  Thus, use the permissive
+           ;; 'read-maybe-utf8-string'.
+           (let ((s (read-maybe-utf8-string p)))
              (display s (current-build-output-port))
              (when (string-any %newlines s)
                (flush-output-port (current-build-output-port)))
              #f))
           ((= k %stderr-error)
            ;; Report an error.
-           (let ((error  (read-latin1-string p))
+           (let ((error  (read-maybe-utf8-string p))
                  ;; Currently the daemon fails to send a status code for early
                  ;; errors like DB schema version mismatches, so check for EOF.
                  (status (if (and (>= (nix-server-minor-version server) 8)