Bug 108528 - knob is not defined doesn't explain to 2001110503 users what to do

CGI.pl

@@ -111,10 +111,11 @@ sub CheckFormField (\%$;\@) {
 sub CheckFormFieldDefined (\%$) {
     my ($formRef,                # a reference to the form to check (a hash)
         $fieldname,              # the fieldname to check
+        $info,                   # (optional) error message to give
        ) = @_;
 
     if (!defined $formRef->{$fieldname}) {
-        ThrowCodeError("undefined_field", { field => $fieldname });
+        ThrowCodeError("undefined_field", { field => $fieldname, info => $info });
     }
 }
 

process_bug.cgi

@@ -858,7 +858,7 @@ if (defined $::FORM{newcc} || defined $::FORM{removecc} || defined $::FORM{massc
 }
 
 
-CheckFormFieldDefined(\%::FORM, 'knob');
+CheckFormFieldDefined(\%::FORM, 'knob', "check that \"Leave as...\" was selected.");
 SWITCH: for ($::FORM{'knob'}) {
     /^none$/ && do {
         last SWITCH;

template/en/default/global/code-error.html.tmpl

@@ -208,7 +208,12 @@
      I was unable to retrieve your old password from the database.
 
   [% ELSIF error == "undefined_field" %]
-    [% field FILTER html %] was not defined; [% Param('browserbugmessage') %]
+    [% field FILTER html %] was not defined; 
+    [% IF info %]
+      [% info FILTER html %]
+    [% ELSE %]
+      [% Param('browserbugmessage') %]
+    [% END %]
 
   [% ELSIF error == "unknown_action" %]
     [% IF action %]