Search for documents which reference us only if our reference itself is

following format defined in system preference level.

bt5/erp5_dms/SkinTemplateItem/portal_skins/erp5_dms/Base_getImplicitPredecessorValueList.xml

@@ -58,7 +58,8 @@ and make sure we get latest/most relevant version\n
 should be reimplemented in SQL some sunny day.\n
 """\n
 reference = context.getReference()\n
-if reference is None:\n
+if reference is None or not context.isSearchableReference():\n
+  # empty or not following format preference\n
   return ()\n
 \n
 return context.Base_zGetImplicitPredecessorValueList(reference=reference)\n

bt5/erp5_dms/bt/revision

-1269
\ No newline at end of file
+1270
\ No newline at end of file

product/ERP5/Document/Document.py

@@ -317,6 +317,22 @@ class Document(DocumentExtensibleTraversableMixin, XMLObject, UrlMixin,
       preferences.
     """
     text = self.getSearchableText() # XXX getSearchableText or asText ?
+    return self._getSearchableReferenceList(text)
+
+  security.declareProtected(Permissions.AccessContentsInformation, 'getSearchableReferenceList')
+  def isSearchableReference(self):
+    """
+      Determine if current document's reference can be used for searching - i.e. follows
+      certain defined at system level preferences format.
+    """
+    reference = self.getReference()
+    return len(self._getSearchableReferenceList(reference))
+
+  def _getSearchableReferenceList(self, text):
+    """
+      Extract all reference alike strings from text using for that a 
+      regular expression defined at system level preferences.
+    """
     regexp = self.portal_preferences.getPreferredDocumentReferenceRegularExpression()
     try:
       rx_search = re.compile(regexp)