httpd: avoid crash on cgit -> coderepo 404 fallback

A trickled cgit response can cause HTTPD::Async->event_step to
fire an extra time after header parsing.  We need to account for
the lack of async_pass call populating ->{fh} and ->{http} in
that case and avoid calling $self->{fh}->write when there's
no {fh}.

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/PublicInbox/GitHTTPBackend.pm b/lib/PublicInbox/GitHTTPBackend.pm
index 1eb51f27..974a1831 100644
--- a/lib/PublicInbox/GitHTTPBackend.pm
+++ b/lib/PublicInbox/GitHTTPBackend.pm
@@ -128,7 +128,7 @@ sub input_prepare {
         { 0 => $in };
 }
 
-sub parse_cgi_headers {
+sub parse_cgi_headers { # {parse_hdr} for Qspawn
         my ($r, $bref, $ctx) = @_;
         return r(500) unless defined $r && $r >= 0;
         $$bref =~ s/\A(.*?)\r?\n\r?\n//s or return $r == 0 ? r(500) : undef;
@@ -145,7 +145,9 @@ sub parse_cgi_headers {
         }
 
         # fallback to WwwCoderepo if cgit 404s.  Duplicating $ctx prevents
-        # ->finalize from the current Qspawn from using qspawn.wcb
+        # ->finalize from the current Qspawn from using qspawn.wcb.
+        # This makes qspawn skip ->async_pass and causes
+        # PublicInbox::HTTPD::Async::event_step to close shortly after
         if ($code == 404 && $ctx->{www} && !$ctx->{_coderepo_tried}++) {
                 my %ctx = %$ctx;
                 $ctx{env} = +{ %{$ctx->{env}} };