view: msg_html: reduce memory use on reused MIDs

In rare cases where Message-IDs get reused, we do not want to
hold onto the large Email::MIME objects in memory after showing
the first message.  So discard each message as soon as we're
done using it so we can save memory for the next message.

The new and expensive xt/mem-msgview.t test shows a nearly 14MB
reduction for two ~7MB messages.  run_script() also gets
upgraded to make it easier to pass large inputs via IO GLOBs.

2 files changed, 20 insertions, 13 deletions

diff --git a/lib/PublicInbox/TestCommon.pm b/lib/PublicInbox/TestCommon.pm
index 68785969..d6d1e939 100644
--- a/lib/PublicInbox/TestCommon.pm
+++ b/lib/PublicInbox/TestCommon.pm
@@ -195,14 +195,20 @@ sub run_script ($;$$) {
         my $spawn_opt = {};
         for my $fd (0..2) {
                 my $redir = $opt->{$fd};
-                next unless ref($redir);
-                open my $fh, '+>', undef or die "open: $!";
-                $fhref->[$fd] = $fh;
-                $spawn_opt->{$fd} = $fh;
-                next if $fd > 0;
-                $fh->autoflush(1);
-                print $fh $$redir or die "print: $!";
-                seek($fh, 0, SEEK_SET) or die "seek: $!";
+                my $ref = ref($redir);
+                if ($ref eq 'SCALAR') {
+                        open my $fh, '+>', undef or die "open: $!";
+                        $fhref->[$fd] = $fh;
+                        $spawn_opt->{$fd} = $fh;
+                        next if $fd > 0;
+                        $fh->autoflush(1);
+                        print $fh $$redir or die "print: $!";
+                        seek($fh, 0, SEEK_SET) or die "seek: $!";
+                } elsif ($ref eq 'GLOB') {
+                        $spawn_opt->{$fd} = $fhref->[$fd] = $redir;
+                } elsif ($ref) {
+                        die "unable to deal with $ref $redir";
+                }
         }
         if ($run_mode == 0) {
                 # spawn an independent new process, like real-world use cases:
diff --git a/lib/PublicInbox/View.pm b/lib/PublicInbox/View.pm
index c38a1289..69948c4a 100644
--- a/lib/PublicInbox/View.pm
+++ b/lib/PublicInbox/View.pm
@@ -31,8 +31,8 @@ sub msg_html_i {
                 # $more cannot be true w/o $smsg being defined:
                 my $upfx = $more ? '../'.mid_escape($ctx->{smsg}->mid).'/' : '';
                 $ctx->{tip} .
-                        multipart_text_as_html($ctx->{mime}, $upfx, $ctx) .
-                        '</pre><hr>'
+                        multipart_text_as_html(delete $ctx->{mime}, $upfx,
+                                                $ctx) . '</pre><hr>'
         } elsif ($more && @$more) {
                 ++$ctx->{end_nr};
                 msg_html_more($ctx, $more, $nr);
@@ -41,7 +41,7 @@ sub msg_html_i {
                 # we want to at least show the message if something
                 # here crashes:
                 eval {
-                        my $hdr = delete($ctx->{mime})->header_obj;
+                        my $hdr = delete($ctx->{hdr});
                         '<pre>' . html_footer($hdr, 1, $ctx) .
                         '</pre>' . msg_reply($ctx, $hdr)
                 };
@@ -56,7 +56,8 @@ sub msg_html {
         my ($ctx, $mime, $more, $smsg) = @_;
         my $ibx = $ctx->{-inbox};
         $ctx->{-obfs_ibx} = $ibx->{obfuscate} ? $ibx : undef;
-        $ctx->{tip} = _msg_html_prepare($mime->header_obj, $ctx, $more, 0);
+        my $hdr = $ctx->{hdr} = $mime->header_obj;
+        $ctx->{tip} = _msg_html_prepare($hdr, $ctx, $more, 0);
         $ctx->{more} = $more;
         $ctx->{end_nr} = 2;
         $ctx->{smsg} = $smsg;
@@ -95,8 +96,8 @@ sub msg_html_more {
                 my $next = $ibx->over->next_by_mid($mid, \$id, \$prev);
                 @$more = $next ? ($id, $prev, $next) : ();
                 if ($smsg) {
-                        my $mime = $smsg->{mime};
                         my $upfx = '../' . mid_escape($smsg->mid) . '/';
+                        my $mime = delete $smsg->{mime};
                         _msg_html_prepare($mime->header_obj, $ctx, $more, $nr) .
                                 multipart_text_as_html($mime, $upfx, $ctx) .
                                 '</pre><hr>'