graphql: Fix aliased scalar fields

Author: leoyvens

core/tests/interfaces.rs

@@ -1,6 +1,7 @@
 // Tests for graphql interfaces.
 
 use graph::prelude::*;
+use graph_graphql::prelude::object;
 use test_store::*;
 
 // `entities` is `(entity, type)`.
@@ -554,3 +555,48 @@ fn invalid_fragment() {
         e => panic!("error {} is not the expected one", e),
     }
 }
+
+#[test]
+fn alias() {
+    let subgraph_id = "Alias";
+    let schema = "interface Legged { id: ID!, legs: Int! }
+                  type Animal implements Legged @entity {
+                    id: ID!
+                    legs: Int!
+                    parent: Legged
+                  }";
+
+    let query = "query { l: legged(id: \"child\") { ... on Animal { p: parent { i: id, t: __typename } } } }";
+
+    let parent = (
+        Entity::from(vec![
+            ("id", Value::from("parent")),
+            ("legs", Value::from(4)),
+            ("parent", Value::Null),
+        ]),
+        "Animal",
+    );
+    let child = (
+        Entity::from(vec![
+            ("id", Value::from("child")),
+            ("legs", Value::from(3)),
+            ("parent", Value::String("parent".into())),
+        ]),
+        "Animal",
+    );
+
+    let res = insert_and_query(subgraph_id, schema, vec![parent, child], query).unwrap();
+
+    assert!(res.errors.is_none(), format!("{:#?}", res.errors));
+    assert_eq!(
+        res.data.unwrap(),
+        object! {
+            l: object! {
+                p: object! {
+                    i: "parent",
+                    t: "Animal"
+                }
+            }
+        }
+    )
+}

graphql/src/execution/execution.rs

@@ -303,8 +303,10 @@ fn execute_selection_set_to_map(
             let field_value = prefetched_object
                 .as_mut()
                 .map(|o| {
+                    // Prefetched objects associated to `prefetch:response_key`,
+                    // while scalars are associated to the field name.
                     o.remove(&format!("prefetch:{}", response_key))
-                        .or(o.remove(response_key))
+                        .or(o.remove(&fields[0].name))
                 })
                 .flatten();
             match execute_field(&ctx, object_type, field_value, &fields[0], field, fields) {