From 90ad5c8836138b7fd4d1bd0243dfa8b30ae0cf21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Mon, 16 Jan 2017 21:59:00 +0100
Subject: [PATCH] grafts: Actually cache grafts during the derivation DAG
 traversal.

This fixes a regression introduced in
d38bc9a9f6feefc465964531520fee5663a12f48 whereby the cache was
effectively disabled.

Reported by Thomas Danckaert <thomas.danckaert@gmail.com>.

* guix/grafts.scm (with-cache): In the cache miss case, wrap body in
'mbegin'.
---
 guix/grafts.scm | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/guix/grafts.scm b/guix/grafts.scm
index 2006d3908e..b60c8cfd90 100644
--- a/guix/grafts.scm
+++ b/guix/grafts.scm
@@ -222,8 +222,9 @@ available."
        (return result))
       (#f                                         ;cache miss
        (mlet %state-monad ((result (begin exp ...)))
-         (set-current-state (vhash-consq key result cache))
-         (return result))))))
+         (mbegin %state-monad
+           (set-current-state (vhash-consq key result cache))
+           (return result)))))))
 
 (define* (cumulative-grafts store drv grafts
                             references