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https://issues.apache.org/jira/browse/TINKERPOP-2978?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17778767#comment-17778767
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ASF GitHub Bot commented on TINKERPOP-2978:
-------------------------------------------
xiazcy commented on code in PR #2302:
URL: https://github.com/apache/tinkerpop/pull/2302#discussion_r1369007819
##########
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/CombineStep.java:
##########
@@ -0,0 +1,96 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.tinkerpop.gremlin.process.traversal.step.map;
+
+import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
+import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
+import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
+import
org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
+import org.apache.tinkerpop.gremlin.process.traversal.util.ListFunction;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+/**
+ * A map step that returns the combination of the traverser and the provided
arguments. This is also commonly known as
+ * concatenation or append.
+ */
+public final class CombineStep<S, E> extends ScalarMapStep<S, List<?>>
implements TraversalParent, ListFunction {
+ private Traversal.Admin<S, E> valueTraversal;
+ private Object parameterItems;
+
+ public CombineStep(final Traversal.Admin traversal, final Object values) {
+ super(traversal);
+
+ if (values instanceof Traversal) {
+ valueTraversal = integrateChild(((Traversal<S, E>)
values).asAdmin());
+ } else {
+ parameterItems = values;
+ }
+ }
+
+ @Override
+ public String getStepName() { return "combine"; }
+
+ @Override
+ protected List<?> map(Traverser.Admin<S> traverser) {
+ final Collection listA = convertTraverserToCollection(traverser);
+ final Collection listB = (null != valueTraversal) ?
convertTraversalToCollection(traverser, valueTraversal) :
convertArgumentToCollection(parameterItems);
+
+ final List combined = new ArrayList(listA);
+ combined.addAll(listB);
+
+ return combined;
+ }
+
+ @Override
+ public List<Traversal.Admin<S, E>> getLocalChildren() {
+ return (null == valueTraversal) ? Collections.emptyList() :
Collections.singletonList(valueTraversal);
+ }
+
+ @Override
+ public Set<TraverserRequirement> getRequirements() { return
this.getSelfAndChildRequirements(); }
Review Comment:
I think you'd want to pass in the requirement for the self too?
```suggestion
public Set<TraverserRequirement> getRequirements() { return
this.getSelfAndChildRequirements(TraverserRequirement.OBJECT); }
```
> Add List Manipulation Steps to Gremlin
> --------------------------------------
>
> Key: TINKERPOP-2978
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2978
> Project: TinkerPop
> Issue Type: Improvement
> Components: language
> Reporter: Cole Greer
> Priority: Major
>
> Today Gremlin requires that users fall back to closures to handle many common
> list manipulation options that users want to do on data in the graph. This
> is a problem for many users as many of the providers prevent the use of
> closures due to the security risks so for these users there is no way to
> manipulate lists directly.
> A full list of proposed functions and semantics is detailed here:
> https://github.com/apache/tinkerpop/blob/3.7.0/docs/src/dev/future/proposal-3-remove-closures.asciidoc
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