Always return data loader registry from context

fix #287

Author: oliemansm

graphql-java-kickstart/src/main/java/graphql/kickstart/execution/context/DefaultGraphQLContext.java

@@ -1,5 +1,6 @@
 package graphql.kickstart.execution.context;
 
+import java.util.Objects;
 import java.util.Optional;
 import javax.security.auth.Subject;
 import org.dataloader.DataLoaderRegistry;
@@ -15,7 +16,7 @@ public class DefaultGraphQLContext implements GraphQLContext {
   private final DataLoaderRegistry dataLoaderRegistry;
 
   public DefaultGraphQLContext(DataLoaderRegistry dataLoaderRegistry, Subject subject) {
-    this.dataLoaderRegistry = dataLoaderRegistry;
+    this.dataLoaderRegistry = Objects.requireNonNull(dataLoaderRegistry, "dataLoaderRegistry is required");
     this.subject = subject;
   }
 
@@ -29,8 +30,8 @@ public Optional<Subject> getSubject() {
   }
 
   @Override
-  public Optional<DataLoaderRegistry> getDataLoaderRegistry() {
-    return Optional.ofNullable(dataLoaderRegistry);
+  public DataLoaderRegistry getDataLoaderRegistry() {
+    return dataLoaderRegistry;
   }
 
 }

graphql-java-kickstart/src/main/java/graphql/kickstart/execution/context/GraphQLContext.java

@@ -2,6 +2,7 @@
 
 import java.util.Optional;
 import javax.security.auth.Subject;
+import lombok.NonNull;
 import org.dataloader.DataLoaderRegistry;
 
 /**
@@ -15,7 +16,8 @@ public interface GraphQLContext {
   Optional<Subject> getSubject();
 
   /**
-   * @return the Dataloader registry to use for the execution.
+   * @return the Dataloader registry to use for the execution. Must not return <code>null</code>
    */
-  Optional<DataLoaderRegistry> getDataLoaderRegistry();
+  @NonNull DataLoaderRegistry getDataLoaderRegistry();
+
 }

graphql-java-kickstart/src/main/java/graphql/kickstart/execution/input/GraphQLSingleInvocationInput.java

@@ -7,7 +7,6 @@
 import graphql.schema.GraphQLSchema;
 import java.util.Optional;
 import javax.security.auth.Subject;
-import org.dataloader.DataLoaderRegistry;
 
 /**
  * Represents a single GraphQL execution.
@@ -50,7 +49,7 @@ private ExecutionInput createExecutionInput(GraphQLRequest graphQLRequest, Graph
         .context(context)
         .root(root)
         .variables(graphQLRequest.getVariables())
-        .dataLoaderRegistry(context.getDataLoaderRegistry().orElse(new DataLoaderRegistry()))
+        .dataLoaderRegistry(context.getDataLoaderRegistry())
         .executionId(ExecutionId.generate())
         .build();
   }