A few changes to improve robustness. Also some cosmetic changes.

src/calibre/gui2/dialogs/tag_list_editor.py

@@ -31,9 +31,12 @@ class TagListEditor(QDialog, Ui_TagListEditor):
             result = db.get_publishers_with_ids()
             compare = (lambda x,y:cmp(x.lower(), y.lower()))
         else: # should be a custom field
+            self.cc_label = None
+            if category in db.field_metadata:
                 self.cc_label = db.field_metadata[category]['label']
-            print 'here', self.cc_label
                 result = self.db.get_custom_items_with_ids(label=self.cc_label)
+            else:
+                result = []
             compare = (lambda x,y:cmp(x.lower(), y.lower()))
 
         for k,v in result:

src/calibre/gui2/tag_view.py

@@ -135,8 +135,12 @@ class TagsView(QTreeView): # {{{
         if item.type == TagTreeItem.CATEGORY:
             category = unicode(item.name.toString())
             key = item.category_key
+            # Verify that we are working with a field that we know something about
+            if key not in self.db.field_metadata:
+                return True
+
             self.context_menu = QMenu(self)
-            # If the user right-clicked on a tag/series/publisher, then offer
+            # If the user right-clicked on an editable item, then offer
             # the possibility of renaming that item
             if tag_name and \
                     (key in ['authors', 'tags', 'series', 'publisher', 'search'] or \
@@ -378,7 +382,7 @@ class TagsModel(QAbstractItemModel): # {{{
             if category in data: # They should always be there, but ...
                 # make a map of sets of names per category for duplicate
                 # checking when editing
-                self.category_items[category] = [tag.name for tag in data[category]]
+                self.category_items[category] = set([tag.name for tag in data[category]])
                 self.row_map.append(category)
                 self.categories.append(tb_categories[category]['name'])
 
@@ -425,13 +429,16 @@ class TagsModel(QAbstractItemModel): # {{{
             error_dialog(self.tags_view, _('Item is blank'),
                         _('An item cannot be set to nothing. Delete it instead.')).exec_()
             return False
-
         item = index.internalPointer()
         key = item.parent.category_key
+        # make certain we know about the category
+        if key not in self.db.field_metadata:
+            return
         if val in self.category_items[key]:
             error_dialog(self.tags_view, 'Duplicate item',
                         _('The name %s is already used.')%val).exec_()
             return False
+        oldval = item.tag.name
         if key == 'search':
             saved_searches.rename(unicode(item.data(role).toString()), val)
             self.tags_view.search_item_renamed.emit()
@@ -449,7 +456,10 @@ class TagsModel(QAbstractItemModel): # {{{
                                     label=self.db.field_metadata[key]['label'])
             self.tags_view.tag_item_renamed.emit()
         item.tag.name = val
-        self.refresh()
+        self.dataChanged.emit(index, index)
+        # replace the old value in the duplicate detection map with the new one
+        self.category_items[key].discard(oldval)
+        self.category_items[key].add(val)
         return True
 
     def headerData(self, *args):

src/calibre/library/database2.py

@@ -986,6 +986,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
                 self.notify('metadata', [id])
 
     # Convenience methods for tags_list_editor
+    # Note: we generally do not need to refresh_ids because library_view will
+    # refresh everything.
     def get_tags_with_ids(self):
         result = self.conn.get('SELECT id,name FROM tags')
         if not result:
@@ -1017,11 +1019,11 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
     def delete_series_using_id(self, id):
         if id:
             books = self.conn.get('SELECT book from books_series_link WHERE series=?', (id,))
-            for (book_id,) in books:
-                self.conn.execute('UPDATE books SET series_index=1.0 WHERE id=?', (book_id,))
             self.conn.execute('DELETE FROM books_series_link WHERE series=?', (id,))
             self.conn.execute('DELETE FROM series WHERE id=?', (id,))
             self.conn.commit()
+            for (book_id,) in books:
+                self.conn.execute('UPDATE books SET series_index=1.0 WHERE id=?', (book_id,))
 
     def get_publishers_with_ids(self):
         result = self.conn.get('SELECT id,name FROM publishers')
@@ -1040,6 +1042,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             self.conn.execute('DELETE FROM publishers WHERE id=?', (id,))
             self.conn.commit()
 
+    # There is no editor for author, so we do not need get_authors_with_ids or
+    # delete_author_using_id.
     def rename_author(self, id, new_name):
         if id:
             # Make sure that any commas in new_name are changed to '|'!