Tweak default "numeric" grid filter, to ignore UPC-like values

Those tend to cause SQL errors, so just "fail silently" for now.  This
situation needs to be improved on the front end at some point...

tailbone/newgrids/filters.py

@@ -366,12 +366,48 @@ class AlchemyNumericFilter(AlchemyGridFilter):
     """
     value_renderer_factory = NumericValueRenderer
 
-    def default_verbs(self):
-        """
-        Expose greater-than / less-than verbs in addition to core.
-        """
-        return ['equal', 'not_equal', 'greater_than', 'greater_equal',
-                'less_than', 'less_equal', 'is_null', 'is_not_null']
+    # expose greater-than / less-than verbs in addition to core
+    default_verbs = ['equal', 'not_equal', 'greater_than', 'greater_equal',
+                     'less_than', 'less_equal', 'is_null', 'is_not_null']
+
+    # TODO: what follows "works" in that it prevents an error...but from the
+    # user's perspective it still fails silently...need to improve on front-end
+
+    # try to detect (and ignore) common mistake where user enters UPC as search
+    # term for integer field...
+
+    def value_invalid(self, value):
+        return bool(value and len(value) > 8)
+
+    def filter_equal(self, query, value):
+        if self.value_invalid(value):
+            return query
+        return super(AlchemyNumericFilter, self).filter_equal(query, value)
+
+    def filter_not_equal(self, query, value):
+        if self.value_invalid(value):
+            return query
+        return super(AlchemyNumericFilter, self).filter_not_equal(query, value)
+
+    def filter_greater_than(self, query, value):
+        if self.value_invalid(value):
+            return query
+        return super(AlchemyNumericFilter, self).filter_greater_than(query, value)
+
+    def filter_greater_equal(self, query, value):
+        if self.value_invalid(value):
+            return query
+        return super(AlchemyNumericFilter, self).filter_greater_equal(query, value)
+
+    def filter_less_than(self, query, value):
+        if self.value_invalid(value):
+            return query
+        return super(AlchemyNumericFilter, self).filter_less_than(query, value)
+
+    def filter_less_equal(self, query, value):
+        if self.value_invalid(value):
+            return query
+        return super(AlchemyNumericFilter, self).filter_less_equal(query, value)
 
 
 class AlchemyBooleanFilter(AlchemyGridFilter):