From 874e96c2423c772564c9dc63254baa99e86f270b Mon Sep 17 00:00:00 2001
From: Dylan William Hardison <dylan@hardison.net>
Date: Sat, 12 Nov 2016 11:41:08 -0500
Subject: Bug 1314201 - ThrowUserError and ThrowCodeError should print headers
 if headers have not already been printed

---
 Bugzilla/CGI.pm                                 | 23 +++++++++++++++++++----
 Bugzilla/Error.pm                               |  4 ++--
 Bugzilla/Template.pm                            | 13 ++++++++++++-
 template/en/default/global/code-error.html.tmpl |  4 ++++
 4 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/Bugzilla/CGI.pm b/Bugzilla/CGI.pm
index 78987ab71..ec8b8e52b 100644
--- a/Bugzilla/CGI.pm
+++ b/Bugzilla/CGI.pm
@@ -21,6 +21,7 @@ use Bugzilla::Search::Recent;
 
 use File::Basename;
 use URI;
+use Carp qw(cluck);
 
 BEGIN {
     if (ON_WINDOWS) {
@@ -306,7 +307,6 @@ sub check_etag {
     return 0;
 }
 
-# Overwrite to ensure nph doesn't get set, and unset HEADERS_ONCE
 sub multipart_init {
     my $self = shift;
 
@@ -330,6 +330,7 @@ sub multipart_init {
     # CGI.pm's header() sets nph according to a param or $CGI::NPH, which
     # is the desired behaviour.
 
+    $self->{_bz_multipart} = 1;
     return $self->header(
         %param,
     ) . "WARNING: YOUR BROWSER DOESN'T SUPPORT THIS SERVER-PUSH TECHNOLOGY." . $self->multipart_end;
@@ -384,7 +385,12 @@ sub header {
     my %headers;
     my $user = Bugzilla->user;
 
-    # If there's only one parameter, then it's a Content-Type.
+    if ($self->{_bz_headers_sent} && !$self->{_bz_multipart}) {
+        # cluck for the warning log so we can see where this was called.
+        cluck "attempt to send headers after headers already sent!";
+        ThrowCodeError("headers_already_sent");
+    }
+
     if (scalar(@_) == 1) {
         %headers = ('-type' => shift(@_));
     }
@@ -460,9 +466,18 @@ sub header {
     Bugzilla::Hook::process('cgi_headers',
         { cgi => $self, headers => \%headers }
     );
-    $self->{_header_done} = 1;
 
-    return $self->SUPER::header(%headers) || "";
+    my $headers = $self->SUPER::header(%headers) || "";
+    if ($headers && Bugzilla->usage_mode != USAGE_MODE_XMLRPC) {
+        $self->{_bz_headers_sent} = 1;
+    }
+
+    return $headers;
+}
+
+sub sent_headers {
+    my ($self) = @_;
+    return $self->{_bz_headers_sent};
 }
 
 sub param {
diff --git a/Bugzilla/Error.pm b/Bugzilla/Error.pm
index fc0e4812e..226078f9c 100644
--- a/Bugzilla/Error.pm
+++ b/Bugzilla/Error.pm
@@ -112,7 +112,7 @@ sub _throw_error {
         }
 
         my $cgi = Bugzilla->cgi;
-        $cgi->close_standby_message('text/html', 'inline', 'error', 'html');
+        $cgi->close_standby_message('text/html', 'inline', 'error', 'html') unless $cgi->sent_headers;
         $template->process($name, $vars)
           || ThrowTemplateError($template->error());
         print $cgi->multipart_final() if $cgi->{_multipart_in_progress};
@@ -279,7 +279,7 @@ sub ThrowErrorPage {
         my $template = Bugzilla->template;
         my $vars = {};
         $vars->{message} = $message;
-        print $cgi->header();
+        print $cgi->header() unless $cgi->sent_headers();
         $template->process($template_name, $vars)
           || ThrowTemplateError($template->error());
         exit;
diff --git a/Bugzilla/Template.pm b/Bugzilla/Template.pm
index eb1496fca..dec9885c2 100644
--- a/Bugzilla/Template.pm
+++ b/Bugzilla/Template.pm
@@ -653,10 +653,21 @@ our $is_processing = 0;
 
 sub process {
     my $self = shift;
+    my ($template, undef, $output) = @_;
+
+    if (!$output && Bugzilla->usage_mode == USAGE_MODE_BROWSER) {
+        # if $output is not passed, this will print.
+        my $cgi = Bugzilla->cgi;
+        unless ($cgi->sent_headers) {
+            warn "attempted to process $template before sending headers!";
+            print $cgi->header();
+        }
+    }
+
     # All of this current_langs stuff allows template_inner to correctly
     # determine what-language Template object it should instantiate.
     my $current_langs = Bugzilla->request_cache->{template_current_lang} ||= [];
-    unshift(@$current_langs, $self->context->{bz_language});
+    unshift @$current_langs, $self->context->{bz_language};
     local $is_processing = 1;
     my $retval = $self->SUPER::process(@_);
     shift @$current_langs;
diff --git a/template/en/default/global/code-error.html.tmpl b/template/en/default/global/code-error.html.tmpl
index 18650de7d..f78c954d7 100644
--- a/template/en/default/global/code-error.html.tmpl
+++ b/template/en/default/global/code-error.html.tmpl
@@ -198,6 +198,10 @@
     [% title = "Field Type Not Specified" %]
     You must specify a type when creating a custom field.
 
+  [% ELSIF error == "headers_already_sent" %]
+    [% title = "Tried to send headers twice" %]
+    Somewhere inside [% terms.Bugzilla %], code attempted to sent HTTP headers more than once.
+
   [% ELSIF error == "illegal_content_type_method" %]
     Your form submission got corrupted somehow.  The <em>content
     method</em> field, which specifies how the content type gets determined,
-- 
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