From 0220e401cd68256c2c0231284f566885cd7b07ba Mon Sep 17 00:00:00 2001
From: Lance Edgar <lance@edbob.org>
Date: Fri, 4 Dec 2020 15:26:21 -0600
Subject: [PATCH] Add "is empty" and related verbs, for "string" type grid
 filters

---
 tailbone/grids/filters.py | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/tailbone/grids/filters.py b/tailbone/grids/filters.py
index 9d08c881..02ca9130 100644
--- a/tailbone/grids/filters.py
+++ b/tailbone/grids/filters.py
@@ -134,19 +134,33 @@ class GridFilter(object):
         'greater_equal':        "greater than or equal to",
         'less_than':            "less than",
         'less_equal':           "less than or equal to",
+        'is_empty':             "is empty",
+        'is_not_empty':         "is not empty",
         'is_null':              "is null",
         'is_not_null':          "is not null",
         'is_true':              "is true",
         'is_false':             "is false",
         'is_false_null':        "is false or null",
+        'is_empty_or_null':     "is either empty or null",
         'contains':             "contains",
         'does_not_contain':     "does not contain",
         'is_me':                "is me",
         'is_not_me':            "is not me",
     }
 
-    valueless_verbs = ['is_any', 'is_null', 'is_not_null', 'is_true', 'is_false',
-                       'is_false_null', 'is_me', 'is_not_me']
+    valueless_verbs = [
+        'is_any',
+        'is_empty',
+        'is_not_empty',
+        'is_null',
+        'is_not_null',
+        'is_true',
+        'is_false',
+        'is_false_null',
+        'is_empty_or_null',
+        'is_me',
+        'is_not_me',
+    ]
 
     value_renderer_factory = DefaultValueRenderer
     data_type = 'string'        # default, but will be set from value renderer
@@ -380,7 +394,11 @@ class AlchemyStringFilter(AlchemyGridFilter):
         Expose contains / does-not-contain verbs in addition to core.
         """
         return ['contains', 'does_not_contain',
-                'equal', 'not_equal', 'is_null', 'is_not_null', 'is_any']
+                'equal', 'not_equal',
+                'is_empty', 'is_not_empty',
+                'is_null', 'is_not_null',
+                'is_empty_or_null',
+                'is_any']
 
     def filter_contains(self, query, value):
         """
@@ -408,6 +426,17 @@ class AlchemyStringFilter(AlchemyGridFilter):
                   for v in value.split()]),
         ))
 
+    def filter_is_empty(self, query, value):
+        return query.filter(sa.func.trim(self.column) == self.encode_value(''))
+
+    def filter_is_not_empty(self, query, value):
+        return query.filter(sa.func.trim(self.column) != self.encode_value(''))
+
+    def filter_is_empty_or_null(self, query, value):
+        return query.filter(
+            sa.or_(
+                sa.func.trim(self.column) == self.encode_value(''),
+                self.column == None))
 
 class AlchemyEmptyStringFilter(AlchemyStringFilter):
     """