Fix the problem that `EmptyMutation` may cause when used in `MergedObject`. #694

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Fix the problem that `EmptyMutation` may cause when used in `MergedObject`. [#694](https://github.com/async-graphql/async-graphql/issues/694)
+
+## [2.11.1] 2021-11-07
+
 - Add `chrono::Duration` custom scalar. [#689](https://github.com/async-graphql/async-graphql/pull/689)
 - Implement `From<Option<Option<T>>>` for `MaybeUndefined<T>`.
 - Add `MaybeUndefined::as_opt_ref`, `MaybeUndefined::as_opt_deref`, `MaybeUndefined::map`, `MaybeUndefined::map_value`, `MaybeUndefined::contains`, `MaybeUndefined::contains_value`, and `MaybeUndefined::transpose` methods.

src/types/empty_mutation.rs

@@ -57,7 +57,7 @@ impl ContainerType for EmptyMutation {
     }
 
     async fn resolve_field(&self, _ctx: &Context<'_>) -> ServerResult<Option<Value>> {
-        unreachable!()
+        Ok(None)
     }
 }
 

tests/merged_object.rs

@@ -401,3 +401,30 @@ pub async fn test_issue_539() {
         })
     )
 }
+
+#[tokio::test]
+pub async fn test_issue_694() {
+    struct Query;
+
+    #[Object]
+    impl Query {
+        async fn test(&self) -> bool {
+            true
+        }
+    }
+
+    #[derive(MergedObject)]
+    pub struct QueryRoot(Query, EmptyMutation);
+
+    let schema = Schema::new(
+        QueryRoot(Query, EmptyMutation),
+        EmptyMutation,
+        EmptySubscription,
+    );
+    assert_eq!(
+        schema.execute("{ test }").await.into_result().unwrap().data,
+        value!({
+            "test": true,
+        })
+    );
+}