newdb: Fix sorting of is_multiple fields

Fix sorting of book list by multi-valued fields like tags not correct in
the new backend. Fixes #1215820 [different ordering by tags in the 1.0 version](https://bugs.launchpad.net/calibre/+bug/1215820)

src/calibre/db/fields.py

@@ -13,7 +13,7 @@ from collections import defaultdict, Counter
 
 from calibre.db.tables import ONE_ONE, MANY_ONE, MANY_MANY, null
 from calibre.db.write import Writer
-from calibre.ebooks.metadata import title_sort
+from calibre.ebooks.metadata import title_sort, author_to_author_sort
 from calibre.utils.config_base import tweaks
 from calibre.utils.icu import sort_key
 from calibre.utils.date import UNDEFINED_DATE
@@ -48,6 +48,10 @@ class Field(object):
             self._sort_key = lambda x:sort_key(calibre_langcode_to_name(x))
         self.is_multiple = (bool(self.metadata['is_multiple']) or self.name ==
                 'formats')
+        self.sort_sort_key = True
+        if self.is_multiple and '&' in self.metadata['is_multiple']['list_to_ui']:
+            self._sort_key = lambda x: sort_key(author_to_author_sort(x))
+            self.sort_sort_key = False
         self.default_value = {} if name == 'identifiers' else () if self.is_multiple else None
         self.category_formatter = type(u'')
         if dt == 'rating':
@@ -378,9 +382,9 @@ class ManyToManyField(Field):
         all_cids = set()
         for cids in ans.itervalues():
             all_cids = all_cids.union(set(cids))
-        sk_map = {cid: self._sort_key(self.table.id_map[cid])
+        sk_map = {cid: self._sort_key(self.table.id_map[cid]) for cid in all_cids}
-                for cid in all_cids}
+        sort_func = (lambda x:tuple(sorted(x))) if self.sort_sort_key else tuple
-        return {id_: (tuple(sk_map[cid] for cid in cids) if cids else
+        return {id_: (sort_func(sk_map[cid] for cid in cids) if cids else
                         (self._default_sort_key,))
                 for id_, cids in ans.iteritems()}
 

src/calibre/db/tests/reading.py

@@ -161,6 +161,25 @@ class ReadingTest(BaseTest):
         # Test subsorting
         self.assertEqual([3, 2, 1], cache.multisort([('identifiers', True),
             ('title', True)]), 'Subsort failed')
+
+        # Test sorting of is_multiple fields.
+
+        # Author like fields should be sorted by generating sort names from the
+        # actual values in entry order
+        for field in ('authors', '#authors'):
+            self.assertEqual(
+                cache.set_field(field, {1:('aa bb', 'bb cc', 'cc dd'), 2:('bb aa', 'xx yy'), 3: ('aa bb', 'bb aa')}), {1, 2, 3})
+            self.assertEqual([2, 3, 1], cache.multisort([(field, True)], ids_to_sort=(1, 2, 3)))
+            self.assertEqual([1, 3, 2], cache.multisort([(field, False)], ids_to_sort=(1, 2, 3)))
+
+        # All other is_multiple fields should be sorted by sorting the values
+        # for each book and using that as the sort key
+        for field in ('tags', '#tags'):
+            self.assertEqual(
+                cache.set_field(field, {1:('b', 'a'), 2:('c', 'y'), 3: ('b', 'z')}), {1, 2, 3})
+            self.assertEqual([1, 3, 2], cache.multisort([(field, True)], ids_to_sort=(1, 2, 3)))
+            self.assertEqual([2, 3, 1], cache.multisort([(field, False)], ids_to_sort=(1, 2, 3)))
+
     # }}}
 
     def test_get_metadata(self):  # {{{

src/calibre/gui2/library/models.py

@@ -685,7 +685,7 @@ class BooksModel(QAbstractTableModel):  # {{{
             elif dt in {'text', 'comments', 'composite', 'enumeration'}:
                 if m['is_multiple'] and not field_obj.is_composite:
                     jv = m['is_multiple']['list_to_ui']
-                    do_sort = field == 'tags'
+                    do_sort = '&' not in jv
                     if do_sort:
                         def func(idx):
                             return QVariant(jv.join(sorted(fffunc(field_obj, idfunc(idx), default_value=()), key=sort_key)))