Refactor code to get list of sortable fields

src/calibre/gui2/actions/sort.py

@@ -53,18 +53,10 @@ class SortByAction(InterfaceAction):
         except TypeError:
             sort_col, order = 'date', True
         fm = db.field_metadata
-        def get_name(k):
-            ans = fm[k]['name']
-            if k == 'cover':
-                ans = _('Has cover')
-            return ans
-
-        name_map = {get_name(k):k for k in fm.sortable_field_keys() if fm[k]['name']}
+        name_map = {v:k for k, v in fm.ui_sortable_field_keys().iteritems()}
         self._sactions = []
         for name in sorted(name_map, key=sort_key):
             key = name_map[name]
-            if key in {'sort', 'series_sort', 'formats', 'path'}:
-                continue
             if key == 'ondevice' and self.gui.device_connected is None:
                 continue
             ascending = None

src/calibre/library/field_metadata.py

@@ -448,6 +448,15 @@ class FieldMetadata(dict):
                 if self._tb_cats[k]['kind']=='field' and
                    self._tb_cats[k]['datatype'] is not None]
 
+    def ui_sortable_field_keys(self):
+        ans = {k:self._tb_cats[k]['name'] for k in set(self.sortable_field_keys()) - {
+            'sort', 'author_sort', 'au_map', 'series_sort', 'marked',
+            'series_index', 'path', 'formats', 'identifiers', 'uuid',
+            'comments',
+        } if self._tb_cats[k]['name']}
+        ans['cover'] = _('Has cover')
+        return ans
+
     def displayable_field_keys(self):
         return [k for k in self._tb_cats.keys()
                 if self._tb_cats[k]['kind']=='field' and

src/calibre/srv/code.py

@@ -107,6 +107,8 @@ def interface_data(ctx, rd):
         raise HTTPNotFound('Invalid number of books: %r' % rd.query.get('num'))
     with db.safe_read_lock:
         ans['search_result'] = search_result(ctx, rd, db, '', num, 0, ','.join(sorts), ','.join(orders))
+        ans['sortable_fields'] = sf = db.field_metadata.ui_sortable_field_keys()
+        sf.pop('ondevice', None)
         ans['field_metadata'] = db.field_metadata.all_metadata()
         # ans['categories'] = ctx.get_categories(rd, db)
         mdata = ans['metadata'] = {}