return empty response when subscription are running on the internal introspection service

lib/src/main/java/graphql/nadel/engine/blueprint/IntrospectionService.kt

@@ -4,12 +4,13 @@ import graphql.ExecutionInput
 import graphql.GraphQL
 import graphql.GraphqlErrorHelper.toSpecification
 import graphql.language.AstPrinter
+import graphql.language.OperationDefinition
 import graphql.nadel.NadelDefinitionRegistry
+import graphql.nadel.NadelServiceExecutionResultImpl
 import graphql.nadel.Service
 import graphql.nadel.ServiceExecution
 import graphql.nadel.ServiceExecutionParameters
 import graphql.nadel.ServiceExecutionResult
-import graphql.nadel.NadelServiceExecutionResultImpl
 import graphql.nadel.engine.util.makeFieldCoordinates
 import graphql.nadel.engine.util.toBuilder
 import graphql.nadel.engine.util.toBuilderWithoutTypes
@@ -40,6 +41,9 @@ open class NadelDefaultIntrospectionRunner(schema: GraphQLSchema) : ServiceExecu
         .build()
 
     override fun execute(serviceExecutionParameters: ServiceExecutionParameters): CompletableFuture<ServiceExecutionResult> {
+        if (serviceExecutionParameters.operationDefinition.operation == OperationDefinition.Operation.SUBSCRIPTION) {
+            return CompletableFuture.completedFuture(NadelServiceExecutionResultImpl())
+        }
         return graphQL
             .executeAsync(
                 ExecutionInput.newExecutionInput()

test/src/test/kotlin/graphql/nadel/tests/hooks/remove-fields.kt

@@ -101,6 +101,18 @@ class `top-level-field-is-removed` : EngineTestHook {
     override fun makeExecutionHints(builder: NadelExecutionHints.Builder) = builder.shortCircuitEmptyQuery { true }
 }
 
+@UseHook
+class `top-level-field-is-removed-for-a-subscription` : EngineTestHook {
+    override val customTransforms = listOf(RemoveFieldTestTransform())
+    override fun makeExecutionHints(builder: NadelExecutionHints.Builder) = builder.shortCircuitEmptyQuery { true }
+}
+
+@UseHook
+class `top-level-field-is-removed-for-a-subscription-with-namespaced-field` : EngineTestHook {
+    override val customTransforms = listOf(RemoveFieldTestTransform())
+    override fun makeExecutionHints(builder: NadelExecutionHints.Builder) = builder.shortCircuitEmptyQuery { true }
+}
+
 @UseHook
 class `top-level-field-is-removed-hint-is-off` : EngineTestHook {
     override val customTransforms = listOf(RemoveFieldTestTransform())

test/src/test/resources/fixtures/field removed/top-level-field-is-removed-for-a-subscription-with-namespaced-field.yml

@@ -0,0 +1,60 @@
+name: "top level field is removed for a subscription with namespaced field"
+enabled: true
+# language=GraphQL
+overallSchema:
+  CommentService: |
+    directive @toBeDeleted on FIELD_DEFINITION
+    type Query {
+      commentById(id: ID): Comment @toBeDeleted
+    }
+    type Subscription {
+      commentsApi: CommentsApi @namespaced
+    }
+    type CommentsApi {
+      onCommentUpdated(id: ID): Comment @toBeDeleted
+    }
+    type Comment {
+      id: ID
+    }
+# language=GraphQL
+underlyingSchema:
+  CommentService: |
+    type Query {
+      commentById(id: ID): Comment
+    }
+    type Subscription {
+      commentsApi: CommentsApi
+    }
+    type CommentsApi {
+      onCommentUpdated(id: ID): Comment
+    }
+    type Comment {
+      id: ID
+    }
+# language=GraphQL
+query: |
+  subscription {
+    commentsApi {
+      onCommentUpdated(id: "C1") {
+        id
+      }
+    }
+  }
+variables: { }
+serviceCalls: [ ]
+# language=JSON
+response: |-
+  {
+    "errors": [
+      {
+        "locations": [],
+        "message": "null",
+        "extensions": {
+          "classification": "ValidationError"
+        }
+      }
+    ],
+    "data": {
+      "commentsApi": null
+    }
+  }

test/src/test/resources/fixtures/field removed/top-level-field-is-removed-for-a-subscription.yml

@@ -0,0 +1,52 @@
+name: "top level field is removed for a subscription"
+enabled: true
+# language=GraphQL
+overallSchema:
+  CommentService: |
+    directive @toBeDeleted on FIELD_DEFINITION
+    type Query {
+      commentById(id: ID): Comment
+    }
+    type Subscription {
+      onCommentUpdated(id: ID): Comment @toBeDeleted
+    }
+    type Comment {
+      id: ID
+    }
+# language=GraphQL
+underlyingSchema:
+  CommentService: |
+    type Query {
+      commentById(id: ID): Comment
+    }
+    type Subscription {
+      onCommentUpdated(id: ID): Comment
+    }
+    type Comment {
+      id: ID
+    }
+# language=GraphQL
+query: |
+  subscription {
+    onCommentUpdated(id: "C1") {
+      id
+    }
+  }
+variables: { }
+serviceCalls: [ ]
+# language=JSON
+response: |-
+  {
+    "errors": [
+      {
+        "locations": [],
+        "message": "null",
+        "extensions": {
+          "classification": "ValidationError"
+        }
+      }
+    ],
+    "data": {
+      "onCommentUpdated": null
+    }
+  }

test/src/test/resources/fixtures/introspection/no-introspections-on-subscriptions.yml

@@ -0,0 +1,52 @@
+name: "no introspections on subscriptions"
+enabled: true
+# language=GraphQL
+overallSchema:
+  MyService: |
+    type Query {
+      comment: Comment
+    }
+    type Subscription {
+      onComment: Comment @namespaced
+    }
+    type Comment {
+      id: ID
+    }
+# language=GraphQL
+underlyingSchema:
+  MyService: |
+    type Query {
+      comment: Comment
+    }
+    type Subscription {
+      onComment: Comment
+    }
+    type Comment {
+      id: ID
+    }
+# language=GraphQL
+query: |
+  subscription {
+    __typename
+  }
+variables: { }
+serviceCalls: [ ]
+# language=JSON
+response: |-
+  {
+    "data": null,
+    "errors": [
+      {
+        "message": "Validation error (SubscriptionIntrospectionRootField) : Subscription operation 'null' root field '__typename' cannot be an introspection field",
+        "locations": [
+          {
+            "line": 2,
+            "column": 3
+          }
+        ],
+        "extensions": {
+          "classification": "ValidationError"
+        }
+      }
+    ]
+  }