i3status-wrapper: don't ignore decoding errors in monitoring loop

1 files changed, 32 insertions, 19 deletions

diff --git a/scripts/desktop/i3status-wrapper b/scripts/desktop/i3status-wrapper
index 97c76034..91f83032 100755
--- a/scripts/desktop/i3status-wrapper
+++ b/scripts/desktop/i3status-wrapper
@@ -60,6 +60,11 @@ unless (fork // die "couldn't fork()!") {
 
     # Read lines forever, ignore a comma at the beginning if it exists.
     while (my ($statusline) = (<> =~ /^,?(.*)/)) {
+	# If there is a decoding error, just skip this line, to minimise
+	# status bar freezes.  This should be fine here because this filtering
+	# loop is in itself stateless.  It's only if the decoding error
+	# involves newlines in the wrong places, or similar, that this skip
+	# could cause us to produce invalid output.
         my $blocks = eval { decode_json $statusline } // next;
 
         unshift @$blocks,
@@ -97,26 +102,34 @@ while (@trees) {
     }
 }
 
-while (my $event = eval { decode_json <$events> } // next) {
-    if ($event->{change} eq "mark") {
-        if (grep $_ eq "caffeinated", $event->{container}{marks}->@*) {
-	    register_caffeinated($event->{container});
-        } elsif ($caffeinated_id
-            and $caffeinated_id == $event->{container}{id}) {
-            clear_caffeinated();
-        }
-    } elsif ($event->{change} eq "init") {
-	++$workspaces == 2 and wsbuttons("yes");
-    } elsif ($event->{change} eq "empty") {
-	--$workspaces == 1 and wsbuttons("no");
-
-	# For simplicity, only fresh-workspace script calls compact_workspaces
-	# atm.  For greater consistency we could call it here, too, without
-	# supplying a leave_gap argument.
-
-	# compact_workspaces;
+# Now loop forever reading events, assuming no exceptions.
+
+eval {
+    while (my $event = decode_json <$events>) {
+	if ($event->{change} eq "mark") {
+	    if (grep $_ eq "caffeinated", $event->{container}{marks}->@*) {
+		register_caffeinated($event->{container});
+	    } elsif ($caffeinated_id
+		and $caffeinated_id == $event->{container}{id}) {
+		clear_caffeinated();
+	    }
+	} elsif ($event->{change} eq "init") {
+	    ++$workspaces == 2 and wsbuttons("yes");
+	} elsif ($event->{change} eq "empty") {
+	    --$workspaces == 1 and wsbuttons("no");
+	    # For simplicity, only fresh-workspace script calls
+	    # compact_workspaces atm.  For greater consistency we could call
+	    # it here, too, without supplying a leave_gap argument.
+	}
     }
-}
+};
+
+# Here we give up if there's a decoding error.  We can't ignore the problem
+# because we don't want our ideas regarding how many workspaces there are, and
+# whether anything is caffeinated, to get out of sync.
+#
+# The user can use the WM's "reload" command to restart the loop.
+$@ and wsbuttons("yes"), clear_caffeinated();
 
 sub wsbuttons {
     return unless $ENV{XDG_CURRENT_DESKTOP} eq "sway";