From 6b83a74b3c3df08a7e1360e03462164fa2d71532 Mon Sep 17 00:00:00 2001
From: Geoffroy Couprie <geoffroy@apollographql.com>
Date: Thu, 1 Sep 2022 13:38:29 +0200
Subject: [PATCH] do not nullify the entire query if the root operation is not
 present (#1674)

if the root operation was not returned by the subgraph (example: when
there's an error), we should not nullify the entire data objet. Instead,
it's the root operation field that should be null (unless it is not
nullable)

Co-authored-by: Martin Bonnin <martin@mbonnin.net>
---
 NEXT_CHANGELOG.md               |  9 ++++
 apollo-router/src/spec/query.rs | 90 +++++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)

diff --git a/NEXT_CHANGELOG.md b/NEXT_CHANGELOG.md
index 7c3a769f92..7fd7c22e34 100644
--- a/NEXT_CHANGELOG.md
+++ b/NEXT_CHANGELOG.md
@@ -63,6 +63,15 @@ The 2.1.1 release of the query planner fixes an issue with the `@defer` directiv
 
 By [@Geal](https://github.com/Geal) in https://github.com/apollographql/router/pull/1650 and https://github.com/apollographql/router/pull/1672
 
+### Do not nullify the entire query if the root operation is not present ([PR #1674](https://github.com/apollographql/router/issues/1674))
+
+if a root field was not returned by the subgraph (example: when
+there's an error), we should not nullify the entire data objet. Instead,
+it's the root field that should be null (unless it is non
+nullable).
+
+By [@Geal](https://github.com/Geal) in https://github.com/apollographql/router/pull/1674
+
 ## 🛠 Maintenance
 
 ### Remove cache layer ([PR #1647](https://github.com/apollographql/router/pull/1647))
diff --git a/apollo-router/src/spec/query.rs b/apollo-router/src/spec/query.rs
index f430b4a336..53e87f86a6 100644
--- a/apollo-router/src/spec/query.rs
+++ b/apollo-router/src/spec/query.rs
@@ -581,6 +581,8 @@ impl Query {
                         }
                     } else if field_type.is_non_null() {
                         return Err(InvalidValue);
+                    } else {
+                        output.insert(field_name.clone(), Value::Null);
                     }
                 }
                 Selection::InlineFragment {
@@ -5574,4 +5576,92 @@ mod tests {
             }},
         );
     }
+
+    #[test]
+    fn query_operation_nullification() {
+        assert_format_response!(
+            "type Query {
+                get: Thing
+            }
+            type Thing {
+                name: String
+            }
+            ",
+            "{
+                get {
+                    name
+                }
+            }",
+            json! {{}},
+            None,
+            json! {{
+                "get": null,
+            }},
+        );
+
+        assert_format_response!(
+            "type Query {
+                get: Thing
+            }
+            type Thing {
+                name: String
+            }
+            ",
+            "query {
+               ...F
+            }
+            
+            fragment F on Query {
+                get {
+                    name
+                }
+            }
+            ",
+            json! {{}},
+            None,
+            json! {{
+                "get": null,
+            }},
+        );
+
+        assert_format_response!(
+            "type Query {
+                get: Thing
+            }
+            type Thing {
+                name: String
+            }
+            ",
+            "query {
+               ... on Query {
+                get {
+                    name
+                }
+               }
+            }",
+            json! {{}},
+            None,
+            json! {{
+                "get": null,
+            }},
+        );
+
+        assert_format_response!(
+            "type Query {
+                get: Thing!
+            }
+            type Thing {
+                name: String
+            }
+            ",
+            "{
+                get {
+                    name
+                }
+            }",
+            json! {{}},
+            None,
+            Value::Null,
+        );
+    }
 }