[jira] [Created] (TINKERPOP-2926) Gremlin-Java > An UnsupportedOperationException occurs on calling next() after a merge step with the option step modulator if the element does not exist

[Andrew Kirk (Jira)]

Andrew Kirk created TINKERPOP-2926:
--------------------------------------

             Summary: Gremlin-Java > An UnsupportedOperationException occurs on 
calling next() after a merge step with the option step modulator if the element 
does not exist
                 Key: TINKERPOP-2926
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2926
             Project: TinkerPop
          Issue Type: Bug
          Components: driver
    Affects Versions: 3.6.2
            Reporter: Andrew Kirk
         Attachments: MergeTestApp.java

Using Gremlin-Java, when the option step modulator is used in combination with 
a merge step, an `UnsupportedOperationException` is thrown upon calling 
`next()` if the specified element does not already exist.

Using an example from the docs, the following construct works fine in the 
console if the element does not already exist:

{code:groovy}
gremlin> g.mergeV([(T.id):300]). 
  option(Merge.onCreate,[(T.label):'Dog', name:'Toby', age:10]).
  option(Merge.onMatch,[age:11])
{code}

But, if we try to do the same thing in Java, we'll get an exception:

{code:java}
g.mergeV(Map.of(T.id, 300))
                .option(
                        Merge.onCreate,
                        Map.of(
                                T.label, "Dog",
                                "name", "Toby",
                                "age", 10
                        )
                )
                .option(
                        Merge.onMatch,
                        Map.of("age", 11)
                )
                .next();
{code}

Exception:
{noformat}
Exception in thread "main" java.lang.UnsupportedOperationException
        at 
java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:142)
        at 
java.base/java.util.ImmutableCollections$AbstractImmutableMap.putAll(ImmutableCollections.java:1073)
        at 
org.apache.tinkerpop.gremlin.process.traversal.step.map.MergeVertexStep.onCreateMap(MergeVertexStep.java:205)
        at 
org.apache.tinkerpop.gremlin.process.traversal.step.map.MergeVertexStep.flatMap(MergeVertexStep.java:168)
        at 
org.apache.tinkerpop.gremlin.process.traversal.step.map.FlatMapStep.processNextStart(FlatMapStep.java:49)
        at 
org.apache.tinkerpop.gremlin.process.traversal.step.map.MergeStep.processNextStart(MergeStep.java:165)
        at 
org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:135)
        at 
org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.next(AbstractStep.java:40)
        at 
org.apache.tinkerpop.gremlin.process.traversal.util.DefaultTraversal.next(DefaultTraversal.java:249)
        at 
io.integralla.tinkerpop.poc.MergeWithOption.main(MergeWithOption.java:44)
{noformat}

If the element is first added (via an add or merge step), the merge with option 
works as expected.

A full example is provided in the attached MergeTestApp.java



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