msg_iter: support read-only elements

Apparently, it's possible to have read-only bodies in
Email::MIME objects.  Haven't gotten a chance to reliably
reproduce it, though...

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/PublicInbox/MsgIter.pm b/lib/PublicInbox/MsgIter.pm
index e0127ab9..ef0d209f 100644
--- a/lib/PublicInbox/MsgIter.pm
+++ b/lib/PublicInbox/MsgIter.pm
@@ -7,6 +7,7 @@ use warnings;
 use base qw(Exporter);
 our @EXPORT = qw(msg_iter);
 use Email::MIME;
+use Scalar::Util qw(readonly);
 
 # Workaround Email::MIME versions without
 # commit dcef9be66c49ae89c7a5027a789bbbac544499ce
@@ -36,7 +37,14 @@ sub msg_iter ($$) {
                                 @parts = (@sub, @parts);
                         } else {
                                 if ($extra_nl) {
-                                        ${$part->{body}} .= $part->{mycrlf};
+                                        my $lf = $part->{mycrlf};
+                                        my $bref = $part->{body};
+                                        if (readonly($$bref)) {
+                                                my $s = $$bref . $lf;
+                                                $part->{body} = \$s;
+                                        } else {
+                                                $$bref .= $lf;
+                                        }
                                 }
                                 $cb->($p);
                         }