Make tags' values optional

Author: gotocoding-DB

kernel/src/actions/mod.rs

@@ -744,7 +744,7 @@ pub(crate) struct Add {
 
     /// Map containing metadata about this logical file.
     #[cfg_attr(test, serde(skip_serializing_if = "Option::is_none"))]
-    pub tags: Option<HashMap<String, String>>,
+    pub tags: Option<HashMap<String, Option<String>>>,
 
     /// Information about deletion vector (DV) associated with this add action
     #[cfg_attr(test, serde(skip_serializing_if = "Option::is_none"))]
@@ -1111,7 +1111,7 @@ mod tests {
                 StructField::nullable("stats", DataType::STRING),
                 StructField::nullable(
                     "tags",
-                    MapType::new(DataType::STRING, DataType::STRING, false),
+                    MapType::new(DataType::STRING, DataType::STRING, true),
                 ),
                 deletion_vector_field(),
                 StructField::nullable("baseRowId", DataType::LONG),

kernel/src/schema/derive_macro_utils.rs

@@ -66,6 +66,13 @@ impl<K: ToDataType, V: ToDataType> ToDataType for HashMap<K, V> {
     }
 }
 
+// ToDataType impl for maps with nullable values
+impl<K: ToDataType, V: ToDataType> ToDataType for HashMap<K, Option<V>> {
+    fn to_data_type() -> DataType {
+        MapType::new(K::to_data_type(), V::to_data_type(), true).into()
+    }
+}
+
 /// The [`delta_kernel_derive::ToSchema`] macro uses this to convert a struct field's name + type
 /// into a `StructField` definition. A blanket impl for `Option<T: ToDataType>` supports nullable
 /// struct fields, which otherwise default to non-nullable.