Change flag_list to return the empty list on error and clear error.

Change the documentation to tell the caller to call error() after an
empty return to see if an error occurred.

1 files changed, 8 insertions, 4 deletions

diff --git a/perl/Wallet/Object/Base.pm b/perl/Wallet/Object/Base.pm
index fff06f4..b4e5939 100644
--- a/perl/Wallet/Object/Base.pm
+++ b/perl/Wallet/Object/Base.pm
@@ -378,9 +378,11 @@ sub flag_clear {
 }
 
 # List the flags on an object.  Returns a list of flag names, which may be
-# empty.  On error, returns (undef) (a list containing one undefined element).
+# empty.  On error, returns the empty list.  The caller should call error() in
+# this case to determine if an error occurred.
 sub flag_list {
     my ($self) = @_;
+    undef $self->{error};
     my @flags;
     eval {
         my $sql = 'select fl_flag from flags where fl_type = ? and
@@ -395,7 +397,7 @@ sub flag_list {
     if ($@) {
         my $id = $self->{type} . ':' . $self->{name};
         $self->error ("cannot retrieve flags for $id: $@");
-        return (undef);
+        return;
     } else {
         return @flags;
     }
@@ -494,7 +496,7 @@ sub show {
     for (my $i = 0; $i < @data; $i++) {
         if ($attrs[$i][0] eq 'ob_created_by') {
             my @flags = $self->flag_list;
-            if (@flags == 1 and not defined $flags[0]) {
+            if (not @flags and $self->error) {
                 return undef;
             }
             if (@flags) {
@@ -705,7 +707,9 @@ user and host from which the change is made and the time of the change.
 =item flag_list()
 
 List the flags set on an object.  If no flags are set, returns the empty
-list.  On failure, returns the list consisting of one undefined element.
+list.  On failure, returns an empty list.  To distinguish between the empty
+response and an error, the caller should call error() after an empty return.
+It is guaranteed to return undef if there was no error.
 
 =item flag_set(FLAG, PRINCIPAL, HOSTNAME [, DATETIME])