Sorting an interface by child-level entity

Author: kamilkisiela

graphql/src/store/query.rs

@@ -561,22 +561,47 @@ fn build_order_by(
                     })
             }
             OrderByValue::Child(parent_field_name, child_field_name) => {
-                if entity.is_interface() {
-                    return Err(QueryExecutionError::OrderByNotSupportedError(
-                        entity.name().to_owned(),
-                        parent_field_name,
-                    ));
-                }
+                // Finds the field that connects the parent entity with the child entity.
+                // In the case of an interface, we need to find the field on one of the types that implement the interface,
+                // as the `@derivedFrom` directive is only allowed on object types.
+                let field = match entity {
+                    ObjectOrInterface::Object(_) => {
+                        sast::get_field(entity, parent_field_name.as_str()).ok_or_else(|| {
+                            QueryExecutionError::EntityFieldError(
+                                entity.name().to_owned(),
+                                parent_field_name.clone(),
+                            )
+                        })?
+                    }
+                    ObjectOrInterface::Interface(_) => {
+                        let object_types = schema
+                            .types_for_interface()
+                            .get(&EntityType::new(entity.name().to_string()))
+                            .ok_or(QueryExecutionError::EntityFieldError(
+                                entity.name().to_owned(),
+                                parent_field_name.clone(),
+                            ))?;
 
-                let field =
-                    sast::get_field(entity, parent_field_name.as_str()).ok_or_else(|| {
-                        QueryExecutionError::EntityFieldError(
-                            entity.name().to_owned(),
-                            parent_field_name.clone(),
-                        )
-                    })?;
+                        if let Some(first_entity) = object_types.first() {
+                            sast::get_field(first_entity, parent_field_name.as_str()).ok_or_else(
+                                || {
+                                    QueryExecutionError::EntityFieldError(
+                                        entity.name().to_owned(),
+                                        parent_field_name.clone(),
+                                    )
+                                },
+                            )?
+                        } else {
+                            Err(QueryExecutionError::EntityFieldError(
+                                entity.name().to_owned(),
+                                parent_field_name.clone(),
+                            ))?
+                        }
+                    }
+                };
                 let derived = field.is_derived();
                 let base_type = field.field_type.get_base_type();
+
                 let child_entity = schema
                     .object_or_interface(base_type)
                     .ok_or_else(|| QueryExecutionError::NamedTypeError(base_type.into()))?;

graphql/tests/query.rs

@@ -978,7 +978,7 @@ fn can_query_with_sorting_by_child_interface() {
 }
 
 #[test]
-fn can_not_query_interface_with_sorting_by_child_entity() {
+fn can_query_interface_with_sorting_by_child_entity() {
     const QUERY: &str = "
     query {
         desc: medias(first: 100, orderBy: author__name, orderDirection: desc) {
@@ -996,8 +996,27 @@ fn can_not_query_interface_with_sorting_by_child_entity() {
     }";
 
     run_query(QUERY, |result, _| {
-        // Sorting an interface by child-level entity (derived) is not supported
-        assert!(result.has_errors());
+        let author1 = object! { name: "Baden" };
+        let author2 = object! { name: "Goodwill" };
+        let desc_medias = vec![
+            object! { title: "Folk Tune Music Video",       author: author2.clone() },
+            object! { title: "Rock Tune Music Video",       author: author2.clone() },
+            object! { title: "Cheesy Tune Music Video",     author: author2.clone() },
+            object! { title: "Pop Tune Single Cover",       author: author1.clone() },
+            object! { title: "Rock Tune Single Cover",      author: author1.clone() },
+            object! { title: "Cheesy Tune Single Cover",    author: author1.clone() },
+        ];
+        let mut asc_medias = desc_medias.clone();
+
+        asc_medias.reverse();
+
+        let exp = object! {
+            desc: desc_medias,
+            asc: asc_medias,
+        };
+
+        let data = extract_data!(result).unwrap();
+        assert_eq!(data, exp);
     });
 }
 
@@ -1020,8 +1039,27 @@ fn can_not_query_interface_with_sorting_by_derived_child_entity() {
     }";
 
     run_query(QUERY, |result, _| {
-        // Sorting an interface by child-level entity is not supported
-        assert!(result.has_errors());
+        let exp = object! {
+            desc: vec![
+                object! { title: "Rock Tune Music Video", song : object! { title: "Rock Tune" } },
+                object! { title: "Rock Tune Single Cover", song : object! { title: "Rock Tune" } },
+                object! { title: "Pop Tune Single Cover", song : object! { title: "Pop Tune" } },
+                object! { title: "Folk Tune Music Video", song : object! { title: "Folk Tune" } },
+                object! { title: "Cheesy Tune Music Video", song : object! { title: "Cheesy Tune" } },
+                object! { title: "Cheesy Tune Single Cover", song : object! { title: "Cheesy Tune" } },
+            ],
+            asc: vec![
+                object! { title: "Cheesy Tune Single Cover", song : object! { title: "Cheesy Tune" } },
+                object! { title: "Cheesy Tune Music Video", song : object! { title: "Cheesy Tune" } },
+                object! { title: "Folk Tune Music Video", song : object! { title: "Folk Tune" } },
+                object! { title: "Pop Tune Single Cover", song : object! { title: "Pop Tune" } },
+                object! { title: "Rock Tune Single Cover", song : object! { title: "Rock Tune" } },
+                object! { title: "Rock Tune Music Video", song : object! { title: "Rock Tune" } },
+            ]
+        };
+
+        let data = extract_data!(result).unwrap();
+        assert_eq!(data, exp);
     });
 }