added a test

apollo-federation/tests/query_plan/build_query_plan_tests.rs

@@ -1361,3 +1361,53 @@ fn condition_order_router799() {
     "###
     );
 }
+
+#[test]
+fn rebase_non_intersecting_without_dropping_inline_fragment_due_to_directive() {
+    let planner = planner!(
+        Subgraph1: r#"
+          type Query {
+            test: X
+          }
+
+          interface I {
+            i: Int
+          }
+
+          type X implements I {
+            i: Int
+          }
+
+          type Y implements I {
+            i: Int
+          }
+          "#,
+    );
+    assert_plan!(
+        &planner,
+        r#"
+          {
+            test { # type X
+              ... on I { # upcast to I
+                ... @skip(if: false) { # This fragment can't be dropped due to its directive.
+                  ... on Y { # downcast to Y (non-intersecting)
+                    i
+                  }
+                }
+              }
+            }
+          }
+        "#,
+        @r###"
+    QueryPlan {
+      Fetch(service: "Subgraph1") {
+        {
+          test {
+            __typename @include(if: false)
+          }
+        }
+      },
+    }
+    "###
+    );
+}

apollo-federation/tests/query_plan/supergraphs/rebase_non_intersecting_without_dropping_inline_fragment_due_to_directive.graphql

@@ -0,0 +1,71 @@
+# Composed from subgraphs with hash: 8312d6d045a731f70fd2c9ced19d38ac8ae32ff5
+schema
+  @link(url: "https://specs.apollo.dev/link/v1.0")
+  @link(url: "https://specs.apollo.dev/join/v0.4", for: EXECUTION)
+{
+  query: Query
+}
+
+directive @join__directive(graphs: [join__Graph!], name: String!, args: join__DirectiveArguments) repeatable on SCHEMA | OBJECT | INTERFACE | FIELD_DEFINITION
+
+directive @join__enumValue(graph: join__Graph!) repeatable on ENUM_VALUE
+
+directive @join__field(graph: join__Graph, requires: join__FieldSet, provides: join__FieldSet, type: String, external: Boolean, override: String, usedOverridden: Boolean, overrideLabel: String) repeatable on FIELD_DEFINITION | INPUT_FIELD_DEFINITION
+
+directive @join__graph(name: String!, url: String!) on ENUM_VALUE
+
+directive @join__implements(graph: join__Graph!, interface: String!) repeatable on OBJECT | INTERFACE
+
+directive @join__type(graph: join__Graph!, key: join__FieldSet, extension: Boolean! = false, resolvable: Boolean! = true, isInterfaceObject: Boolean! = false) repeatable on OBJECT | INTERFACE | UNION | ENUM | INPUT_OBJECT | SCALAR
+
+directive @join__unionMember(graph: join__Graph!, member: String!) repeatable on UNION
+
+directive @link(url: String, as: String, for: link__Purpose, import: [link__Import]) repeatable on SCHEMA
+
+interface I
+  @join__type(graph: SUBGRAPH1)
+{
+  i: Int
+}
+
+scalar join__DirectiveArguments
+
+scalar join__FieldSet
+
+enum join__Graph {
+  SUBGRAPH1 @join__graph(name: "Subgraph1", url: "none")
+}
+
+scalar link__Import
+
+enum link__Purpose {
+  """
+  `SECURITY` features provide metadata necessary to securely resolve fields.
+  """
+  SECURITY
+
+  """
+  `EXECUTION` features provide metadata necessary for operation execution.
+  """
+  EXECUTION
+}
+
+type Query
+  @join__type(graph: SUBGRAPH1)
+{
+  test: X
+}
+
+type X implements I
+  @join__implements(graph: SUBGRAPH1, interface: "I")
+  @join__type(graph: SUBGRAPH1)
+{
+  i: Int
+}
+
+type Y implements I
+  @join__implements(graph: SUBGRAPH1, interface: "I")
+  @join__type(graph: SUBGRAPH1)
+{
+  i: Int
+}