From 2c15ea798c1bd7df5bede24495fba541c1c84b2d Mon Sep 17 00:00:00 2001
From: Lukas Kalbertodt <lukas.kalbertodt@gmail.com>
Date: Wed, 9 Dec 2020 19:26:59 +0100
Subject: [PATCH] Check type before resolving in inline fragments to fix panic
 when using inline fragments with interfaces (#816, #815)

---
 juniper/src/schema/schema.rs     |  4 +++
 juniper/src/tests/query_tests.rs | 34 ++++++++++++++++++++++++++
 juniper/src/types/async_await.rs | 42 +++++++++++++++++---------------
 juniper/src/types/base.rs        | 28 ++++++++++++---------
 4 files changed, 77 insertions(+), 31 deletions(-)

diff --git a/juniper/src/schema/schema.rs b/juniper/src/schema/schema.rs
index 62f03cc51..261da6422 100644
--- a/juniper/src/schema/schema.rs
+++ b/juniper/src/schema/schema.rs
@@ -51,6 +51,10 @@ where
         QueryT::name(info)
     }
 
+    fn concrete_type_name(&self, context: &Self::Context, info: &Self::TypeInfo) -> String {
+        self.query_type.concrete_type_name(context, info)
+    }
+
     fn resolve_field(
         &self,
         info: &Self::TypeInfo,
diff --git a/juniper/src/tests/query_tests.rs b/juniper/src/tests/query_tests.rs
index d671c5bf6..32d79c1ca 100644
--- a/juniper/src/tests/query_tests.rs
+++ b/juniper/src/tests/query_tests.rs
@@ -1,6 +1,7 @@
 use crate::{
     ast::InputValue,
     executor::Variables,
+    graphql_value,
     schema::model::RootNode,
     tests::fixtures::starwars::schema::{Database, Query},
     types::scalars::{EmptyMutation, EmptySubscription},
@@ -731,3 +732,36 @@ async fn test_object_typename() {
         ))
     );
 }
+
+#[tokio::test]
+async fn interface_inline_fragment_friends() {
+    let doc = r#"{
+        human(id: "1002") {
+            friends {
+                name
+                ... on Human { homePlanet }
+                ... on Droid { primaryFunction }
+            }
+        }
+    }"#;
+    let database = Database::new();
+    let schema = RootNode::new(
+        Query,
+        EmptyMutation::<Database>::new(),
+        EmptySubscription::<Database>::new(),
+    );
+
+    assert_eq!(
+        crate::execute(doc, None, &schema, &Variables::new(), &database).await,
+        Ok((
+            graphql_value!({"human": {
+                "friends": [
+                    {"name": "Luke Skywalker", "homePlanet": "Tatooine"},
+                    {"name": "Leia Organa", "homePlanet": "Alderaan"},
+                    {"name": "R2-D2", "primaryFunction": "Astromech"},
+                ],
+            }}),
+            vec![],
+        ))
+    );
+}
diff --git a/juniper/src/types/async_await.rs b/juniper/src/types/async_await.rs
index 395faf5ef..6979e15ab 100644
--- a/juniper/src/types/async_await.rs
+++ b/juniper/src/types/async_await.rs
@@ -323,26 +323,30 @@ where
                 );
 
                 if let Some(ref type_condition) = fragment.type_condition {
-                    let sub_result = instance
-                        .resolve_into_type_async(
-                            info,
-                            type_condition.item,
-                            Some(&fragment.selection_set[..]),
-                            &sub_exec,
-                        )
-                        .await;
-
-                    if let Ok(Value::Object(obj)) = sub_result {
-                        for (k, v) in obj {
-                            async_values.push(AsyncValueFuture::InlineFragment1(async move {
-                                AsyncValue::Field(AsyncField {
-                                    name: k,
-                                    value: Some(v),
-                                })
-                            }));
+                    // Check whether the type matches the type condition.
+                    let concrete_type_name = instance.concrete_type_name(sub_exec.context(), info);
+                    if type_condition.item == concrete_type_name {
+                        let sub_result = instance
+                            .resolve_into_type_async(
+                                info,
+                                type_condition.item,
+                                Some(&fragment.selection_set[..]),
+                                &sub_exec,
+                            )
+                            .await;
+
+                        if let Ok(Value::Object(obj)) = sub_result {
+                            for (k, v) in obj {
+                                async_values.push(AsyncValueFuture::InlineFragment1(async move {
+                                    AsyncValue::Field(AsyncField {
+                                        name: k,
+                                        value: Some(v),
+                                    })
+                                }));
+                            }
+                        } else if let Err(e) = sub_result {
+                            sub_exec.push_error_at(e, *start_pos);
                         }
-                    } else if let Err(e) = sub_result {
-                        sub_exec.push_error_at(e, *start_pos);
                     }
                 } else {
                     async_values.push(AsyncValueFuture::InlineFragment2(async move {
diff --git a/juniper/src/types/base.rs b/juniper/src/types/base.rs
index 1b395d440..d25f7441d 100644
--- a/juniper/src/types/base.rs
+++ b/juniper/src/types/base.rs
@@ -532,19 +532,23 @@ where
                 );
 
                 if let Some(ref type_condition) = fragment.type_condition {
-                    let sub_result = instance.resolve_into_type(
-                        info,
-                        type_condition.item,
-                        Some(&fragment.selection_set[..]),
-                        &sub_exec,
-                    );
-
-                    if let Ok(Value::Object(object)) = sub_result {
-                        for (k, v) in object {
-                            merge_key_into(result, &k, v);
+                    // Check whether the type matches the type condition.
+                    let concrete_type_name = instance.concrete_type_name(sub_exec.context(), info);
+                    if type_condition.item == concrete_type_name {
+                        let sub_result = instance.resolve_into_type(
+                            info,
+                            type_condition.item,
+                            Some(&fragment.selection_set[..]),
+                            &sub_exec,
+                        );
+
+                        if let Ok(Value::Object(object)) = sub_result {
+                            for (k, v) in object {
+                                merge_key_into(result, &k, v);
+                            }
+                        } else if let Err(e) = sub_result {
+                            sub_exec.push_error_at(e, *start_pos);
                         }
-                    } else if let Err(e) = sub_result {
-                        sub_exec.push_error_at(e, *start_pos);
                     }
                 } else if !resolve_selection_set_into(
                     instance,