made changes to right() function

Author: jthandy

integration_tests/data/cross_db/data_right.csv

@@ -1,4 +1,5 @@
 string_text,length_expression,output
 abcdef,3,def
 fishtown,4,town
-december,5,ember
+december,5,ember
+december,0,

integration_tests/models/cross_db_utils/test_right.sql

@@ -7,6 +7,6 @@ with data as (
 select
 
     {{ dbt_utils.right('string_text', 'length_expression') }} as actual,
-    output as expected
+    coalesce(output, '') as expected
 
 from data

macros/cross_db_utils/right.sql

@@ -13,9 +13,26 @@
 
 {% macro bigquery__right(string_text, length_expression) %}
 
-    substr(
-        {{ string_text }},
-        -1 * ({{ length_expression }})
-    )
+    case when {{ length_expression }} = 0 
+        then ''
+    else 
+        substr(
+            {{ string_text }},
+            -1 * ({{ length_expression }})
+        )
+    end
+
+{%- endmacro -%}
+
+{% macro snowflake__right(string_text, length_expression) %}
+
+    case when {{ length_expression }} = 0 
+        then ''
+    else 
+        right(
+            {{ string_text }},
+            {{ length_expression }}
+        )
+    end
 
 {%- endmacro -%}