Implement result single in sync and async Testkit backends (#1210)

This update enables Testkit tests with `Feature:API:Result.Single` flag.

Author: injectives

testkit-backend/src/main/java/neo4j/org/testkit/backend/channel/handler/TestkitRequestProcessorHandler.java

@@ -37,6 +37,7 @@
 import java.util.function.BiFunction;
 
 import org.neo4j.driver.exceptions.Neo4jException;
+import org.neo4j.driver.exceptions.NoSuchRecordException;
 import org.neo4j.driver.exceptions.UntrustedServerException;
 import org.neo4j.driver.internal.spi.ConnectionPool;
 
@@ -138,7 +139,7 @@ private TestkitResponse createErrorResponse( Throwable throwable )
                                                                 .build() )
                               .build();
         }
-        else if ( isConnectionPoolClosedException( throwable ) || throwable instanceof UntrustedServerException )
+        else if ( isConnectionPoolClosedException( throwable ) || throwable instanceof UntrustedServerException || throwable instanceof NoSuchRecordException )
         {
             String id = testkitState.newId();
             return DriverError.builder()

testkit-backend/src/main/java/neo4j/org/testkit/backend/messages/requests/GetFeatures.java

@@ -66,15 +66,17 @@ public class GetFeatures implements TestkitRequest
             "Optimization:PullPipelining",
             "Feature:API:Result.List",
             "Feature:API:Result.Peek",
-            "Optimization:ResultListFetchAll"
+            "Optimization:ResultListFetchAll",
+            "Feature:API:Result.Single"
     ) );
 
     private static final Set<String> ASYNC_FEATURES = new HashSet<>( Arrays.asList(
             "Feature:Bolt:3.0",
             "Optimization:PullPipelining",
             "Feature:API:Result.List",
             "Feature:API:Result.Peek",
-            "Optimization:ResultListFetchAll"
+            "Optimization:ResultListFetchAll",
+            "Feature:API:Result.Single"
     ) );
 
     @Override

testkit-backend/src/main/java/neo4j/org/testkit/backend/messages/requests/ResultSingle.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package neo4j.org.testkit.backend.messages.requests;
+
+import lombok.Getter;
+import lombok.Setter;
+import neo4j.org.testkit.backend.TestkitState;
+import neo4j.org.testkit.backend.holder.ResultCursorHolder;
+import neo4j.org.testkit.backend.messages.responses.TestkitResponse;
+import reactor.core.publisher.Mono;
+
+import java.util.concurrent.CompletionStage;
+
+import org.neo4j.driver.Record;
+import org.neo4j.driver.async.ResultCursor;
+
+@Setter
+@Getter
+public class ResultSingle implements TestkitRequest
+{
+    private ResultSingleBody data;
+
+    @Override
+    public TestkitResponse process( TestkitState testkitState )
+    {
+        return createResponse( testkitState.getResultHolder( data.getResultId() ).getResult().single() );
+    }
+
+    @Override
+    public CompletionStage<TestkitResponse> processAsync( TestkitState testkitState )
+    {
+        return testkitState.getAsyncResultHolder( data.getResultId() )
+                           .thenApply( ResultCursorHolder::getResult )
+                           .thenCompose( ResultCursor::singleAsync )
+                           .thenApply( this::createResponse );
+    }
+
+    @Override
+    public Mono<TestkitResponse> processRx( TestkitState testkitState )
+    {
+        throw new UnsupportedOperationException( "Single method is not supported by reactive API" );
+    }
+
+    @Override
+    public Mono<TestkitResponse> processReactive( TestkitState testkitState )
+    {
+        throw new UnsupportedOperationException( "Single method is not supported by reactive API" );
+    }
+
+    private neo4j.org.testkit.backend.messages.responses.TestkitResponse createResponse( Record record )
+    {
+        return neo4j.org.testkit.backend.messages.responses.Record.builder()
+                                                                  .data( neo4j.org.testkit.backend.messages.responses.Record.RecordBody.builder()
+                                                                                                                                       .values( record )
+                                                                                                                                       .build() )
+                                                                  .build();
+    }
+
+    @Setter
+    @Getter
+    public static class ResultSingleBody
+    {
+        private String resultId;
+    }
+}

testkit-backend/src/main/java/neo4j/org/testkit/backend/messages/requests/TestkitRequest.java

@@ -42,7 +42,7 @@
         @JsonSubTypes.Type( GetRoutingTable.class ), @JsonSubTypes.Type( TransactionClose.class ),
         @JsonSubTypes.Type( ResultList.class ), @JsonSubTypes.Type( GetConnectionPoolMetrics.class ),
         @JsonSubTypes.Type( ResultPeek.class ), @JsonSubTypes.Type( CheckDriverIsEncrypted.class ),
-        @JsonSubTypes.Type( CypherTypeField.class )
+        @JsonSubTypes.Type( CypherTypeField.class ), @JsonSubTypes.Type( ResultSingle.class )
 } )
 public interface TestkitRequest
 {