Allow setting the "exclusive" sequence of grid filters

i.e. let caller specify that any not included, should be omitted

tailbone/grids/core.py

@@ -28,6 +28,7 @@ from __future__ import unicode_literals, absolute_import
 
 import datetime
 import warnings
+import logging
 
 import six
 from six.moves import urllib
@@ -49,6 +50,9 @@ from tailbone.db import Session
 from tailbone.util import raw_datetime
 
 
+log = logging.getLogger(__name__)
+
+
 class FieldList(list):
     """
     Convenience wrapper for a field list.
@@ -1047,7 +1051,7 @@ class Grid(object):
 
         return render(template, context)
 
-    def set_filters_sequence(self, filters):
+    def set_filters_sequence(self, filters, only=False):
         """
         Explicitly set the sequence for grid filters, using the sequence
         provided.  If the grid currently has more filters than are mentioned in
@@ -1055,11 +1059,20 @@ class Grid(object):
         tacked on at the end.
 
         :param filters: Sequence of filter keys, i.e. field names.
+
+        :param only: If true, then *only* those filters specified will
+           be kept, and all others discarded.  If false then any
+           filters not specified will still be tacked onto the end, in
+           alphabetical order.
         """
         new_filters = gridfilters.GridFilterSet()
         for field in filters:
+            if field in self.filters:
                 new_filters[field] = self.filters.pop(field)
-        for field in self.filters:
+            else:
+                log.warning("field '%s' is not in current filter set", field)
+        if not only:
+            for field in sorted(self.filters):
                 new_filters[field] = self.filters[field]
         self.filters = new_filters