Don't keep "disabled" substituters running

For instance, it's pointless to keep copy-from-other-stores running if
there are no other stores, or download-using-manifests if there are no
manifests.  This also speeds things up because we don't send queries
to those substituters.

1 files changed, 7 insertions, 4 deletions

diff --git a/scripts/download-from-binary-cache.pl.in b/scripts/download-from-binary-cache.pl.in
index 10444dc61bc8..abd1f7b712c4 100644
--- a/scripts/download-from-binary-cache.pl.in
+++ b/scripts/download-from-binary-cache.pl.in
@@ -199,10 +199,6 @@ sub getAvailableCaches {
     return if $gotCaches;
     $gotCaches = 1;
 
-    return if
-        ($Nix::Config::config{"use-binary-caches"} // "true") eq "false" ||
-        ($Nix::Config::config{"untrusted-use-binary-caches"} // "true") eq "false";
-
     sub strToList {
         my ($s) = @_;
         return map { s/\/+$//; $_ } split(/ /, $s);
@@ -543,6 +539,13 @@ sub downloadBinary {
 }
 
 
+# Bail out right away if binary caches are disabled.
+exit 0 if
+    ($Nix::Config::config{"use-binary-caches"} // "true") eq "false" ||
+    ($Nix::Config::config{"untrusted-use-binary-caches"} // "true") eq "false";
+print "\n";
+flush STDOUT;
+
 initCache();