Add support for Buefy datepicker in grid filters

tailbone/grids/filters.py

@@ -52,6 +52,7 @@ class FilterValueRenderer(object):
     """
     Base class for all filter renderers.
     """
+    data_type = 'string'
 
     @property
     def name(self):
@@ -75,6 +76,8 @@ class NumericValueRenderer(FilterValueRenderer):
     """
     Input renderer for numeric values.
     """
+    # TODO
+    # data_type = 'number'
 
     def render(self, value=None, **kwargs):
         kwargs.setdefault('step', '0.001')
@@ -85,6 +88,7 @@ class DateValueRenderer(FilterValueRenderer):
     """
     Input renderer for date values.
     """
+    data_type = 'date'
 
     def render(self, value=None, **kwargs):
         kwargs['data-datepicker'] = 'true'
@@ -143,6 +147,7 @@ class GridFilter(object):
                        'is_me', 'is_not_me']
 
     value_renderer_factory = DefaultValueRenderer
+    data_type = 'string'        # default, but will be set from value renderer
 
     def __init__(self, key, label=None, verbs=None, value_enum=None, value_renderer=None,
                  default_active=False, default_verb=None, default_value=None,
@@ -189,6 +194,7 @@ class GridFilter(object):
             renderer = renderer()
         renderer.filter = self
         self.value_renderer = renderer
+        self.data_type = renderer.data_type
 
     def filter(self, data, verb=None, value=UNSPECIFIED):
         """