css.xml.sax.XAttributeList is broken by design

In the Java interface it was reportedly copied from, getValue can return null to
indicate a missing attribute, but in UNOIDL that's not possible.  The workaround
that implementations of the UNOIDL interface resorted to is apparently to return
an empty string (another option would have been to throw an exception).

But the code in xmlsecurity appears to be written under the ill assumption that
getValueByName would return null for a missing attribute.  What the code as
written actually did check was whether the return value is an empty string
(because it picks the operator ==(OUString const &, sal_Unicode const *)
overload, which happens to treat a null second argument like an empty string).

Ideally, the code in xmlsecurity would have some way to tell a missing attribute
from an empty one (via some extended XAttributeList2, or by iterating over all
getNameByIndex, or ...).  But for none of the affected attributes it seems
expected that the attribute's value could be an empty string, so checking for an
empty string seems to work reasonably well in practice.  So keep it simple and
just check for an empty string properly.

Thanks to Tor for spotting that odd xmlsecurity code.

Change-Id: Ib068ee98ef818683a43309ab4d7c3a4731e8deff

1 files changed, 4 insertions, 2 deletions

diff --git a/offapi/com/sun/star/xml/sax/XAttributeList.idl b/offapi/com/sun/star/xml/sax/XAttributeList.idl
index 65aef1f87c60..51924375edcb 100644
--- a/offapi/com/sun/star/xml/sax/XAttributeList.idl
+++ b/offapi/com/sun/star/xml/sax/XAttributeList.idl
@@ -33,8 +33,10 @@ module com {  module sun {  module star {  module xml {  module sax {
     allow the user to make a copy of the instance.
 
     </p>
-    <p>This interface is an IDL version of the Java interface
-    <em>org.xml.sax.AttributeList</em>.</p>
+    <p>This interface is a poor IDL version of the Java interface
+    <em>org.xml.sax.AttributeList</em>.  For example in getValueByName, it does
+    not allow to distinguish a missing value (for which the Java interface
+    returns null) from an empty string value.</p>
  */
 published interface XAttributeList: com::sun::star::uno::XInterface
 {