Add defaut sort on artist_sort field.

For items and albums, defaulting on artist field if artist field
is empty.

beets/dbcore/query.py

@@ -628,6 +628,36 @@ class FixedFieldSort(Sort):
         order = "ASC" if self.is_ascending else "DESC"
         return "{0} {1}".format(self.field, order)
 
+class SmartArtistSort(Sort):
+    """ Sort Album or Item on artist sort fields, defaulting back on
+        artist field if the sort specific field is empty.
+    """
+    def __init__(self, model_cls, is_ascending=True):
+        self.model_cls = model_cls
+        self.is_ascending = is_ascending
+
+    def select_clause(self):
+        return ""
+
+    def union_clause(self):
+        return ""
+
+    def order_clause(self):
+        order = "ASC" if self.is_ascending else "DESC"
+        if 'albumartist_sort' in self.model_cls._fields:
+            exp1 = 'albumartist_sort'
+            exp2 = 'albumartist'
+        elif 'artist_sort' in self.model_cls_fields:
+            exp1 = 'artist_sort'
+            exp2 = 'artist'
+        else:
+            return ""
+
+        order_str = ('(CASE {0} WHEN NULL THEN {1} '
+                     'WHEN "" THEN {1} '
+                     'ELSE {0} END) {2} ').format(exp1, exp2, order)
+        return order_str
+
 
 def build_sql(model_cls, query, sort_order):
     """ Generate a sql statement (and the values that must be injected into it)

beets/library.py

@@ -29,6 +29,7 @@ from beets.util import bytestring_path, syspath, normpath, samefile
 from beets.util.functemplate import Template
 from beets import dbcore
 from beets.dbcore import types
+from beets.dbcore.query import SmartArtistSort
 import beets
 
 
@@ -1013,11 +1014,11 @@ class Library(dbcore.Database):
     # Querying.
 
     def _fetch(self, model_cls, query, sort_order=None):
-        """Parse a query and fetch. If a sort_order is explicitly given,
-        any sort order specification present in the query string is ignored.
+        """Parse a query and fetch. If a order specification is present in the
+        query string the sort_order argument is ignored.
           """
         (query, sort) = get_query(query, model_cls)
-        sort = sort if sort_order is None else sort_order
+        sort = sort_order if sort is None else sort
 
         return super(Library, self)._fetch(
             model_cls, query, sort
@@ -1025,16 +1026,20 @@ class Library(dbcore.Database):
 
     def albums(self, query=None, sort_order=None):
         """Get a sorted list of :class:`Album` objects matching the
-        given sort order. If a sort_order is explicitly given,
-        any sort order specification present in the query string is ignored.
+        given sort order. If a order specification is present in the query
+        string the sort_order argument is ignored. 
         """
+        if sort_order is None:
+            sort_order = SmartArtistSort(Album)
         return self._fetch(Album, query, sort_order)
 
     def items(self, query=None, sort_order=None):
         """Get a sorted list of :class:`Item` objects matching the given
-        given sort order. If a sort_order is explicitly given,
-        any sort order specification present in the query string is ignored.
+        given sort order. If a order specification is present in the query
+        string the sort_order argument is ignored.
         """
+        if sort_order is None:
+            sort_order = SmartArtistSort(Item)
         return self._fetch(Item, query, sort_order)
 
     # Convenience accessors.