bug 1614: revise GetMarcItem so that info dervies from items table

This should help make the items table more authoritative, and ensures
that the items editor does not blank circulation fields such as
issues.

Signed-off-by: Joshua Ferraro <jmf@liblime.com>

diff --git a/C4/Biblio.pm b/C4/Biblio.pm
index 7559ee2..9169fd7 100755 (executable)
--- a/C4/Biblio.pm
+++ b/C4/Biblio.pm
@@ -1729,23 +1729,49 @@ Returns MARC::Record of the item passed in parameter.
 
 sub GetMarcItem {
     my ( $biblionumber, $itemnumber ) = @_;
-    my $dbh = C4::Context->dbh;
-    my $newrecord = MARC::Record->new();
-    my $marcflavour = C4::Context->preference('marcflavour');
-    
-    my $marcxml = GetXmlBiblio($biblionumber);
-    my $record = MARC::Record->new();
-    $record = MARC::Record::new_from_xml( $marcxml, "utf8", $marcflavour );
-    # now, find where the itemnumber is stored & extract only the item
-    my ( $itemnumberfield, $itemnumbersubfield ) =
-      GetMarcFromKohaField( 'items.itemnumber', '' );
-    my @fields = $record->field($itemnumberfield);
-    foreach my $field (@fields) {
-        if ( $field->subfield($itemnumbersubfield) eq $itemnumber ) {
-            $newrecord->insert_fields_ordered($field);
-        }
-    }
-    return $newrecord;
+
+    # GetMarcItem has been revised so that it does the following:
+    #  1. Gets the item information from the items table.
+    #  2. Converts it to a MARC field for storage in the bib record.
+    #
+    # The previous behavior was:
+    #  1. Get the bib record.
+    #  2. Return the MARC tag corresponding to the item record.
+    #
+    # The difference is that one treats the items row as authoritative,
+    # while the other treats the MARC representation as authoritative
+    # under certain circumstances.
+    #
+    # FIXME - a big one
+    #
+    # As of 2007-11-27, this change hopefully does not introduce
+    # any bugs.  However, it does mean that for code that uses
+    # ModItemInMarconefield to update one subfield (corresponding to
+    # an items column) is now less efficient.
+    #
+    # The API needs to be shifted to the following:
+    #  1. User updates items record.
+    #  2. Linked bib is sent for indexing.
+    # 
+    # The missing step 1.5 is updating the item tag in the bib MARC record
+    # so that the indexes are updated.  Depending on performance considerations,
+    # this may ultimately mean of of the following:
+    #  a. MARC field for item is updated right away.
+    #  b. MARC field for item is updated only as part of indexing.
+    #  c. MARC field for item is never actually stored in bib record; instead
+    #     it is generated only when needed for indexing, item export, and
+    #     (maybe) OPAC display.
+    #
+
+    my $itemrecord = GetItem($itemnumber);
+
+    # Tack on 'items.' prefix to column names so that TransformKohaToMarc will work.
+    # Also, don't emit a subfield if the underlying field is blank.
+    my $mungeditem = { map {  $itemrecord->{$_} ne '' ? ("items.$_" => $itemrecord->{$_}) : ()  } keys %{ $itemrecord } };
+
+    my $itemmarc = TransformKohaToMarc($mungeditem);
+    return $itemmarc;
+
 }