Bill Poole created TINKERPOP-2789:
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Summary: Gremlin.Net cannot distinguish between an array parameter
and a parameter array
Key: TINKERPOP-2789
URL: https://issues.apache.org/jira/browse/TINKERPOP-2789
Project: TinkerPop
Issue Type: Bug
Components: dotnet
Affects Versions: 3.6.1
Reporter: Bill Poole
When an array is passed to a step (e.g., "inject(array)"), Gremlin.Net always
"flattens" the array into separate parameters, assuming it is a parameter list
(e.g., "inject(p1, p2, p3, ...)").
This means that traversals in Gremlin.Net are not strictly correct when passing
an array parameter. For example, this traversal below should actually require
an "unfold" step:
{code:java}
await g.Inject<object>(array).Promise(t => t.ToList()); {code}
i.e., it should be:
{code:java}
await g.Inject<object>(array).Unfold<object>().Promise(t => t.ToList()); {code}
This means that certain traversals like in the [Long
Traversals|https://tinkerpop.apache.org/docs/current/recipes/#long-traversals]
recipe shown below do not work in Gremlin.Net because the "unfold" step needs
to be removed.
{code:java}
g.withSideEffect("rels", relations).
inject(persons).sideEffect(
unfold().
addV("person").
property(id, select("id")).
property("name", select("name")).
property("age", select("age")).
group("m").
by(id).
by(unfold())).
select("rels").unfold().as("r").
addE("knows").
from(select("m").select(select("r").select("from"))).
to(select("m").select(select("r").select("to"))).
property("since", select("since")).iterate() {code}
I recognize that the C# language doesn't allow method overloads to distinguish
between an array parameter and a params array. But as it stands, it is
impossible to pass an array parameter to a step, so I think this needs to be
remedied somehow.
One possible solution could be for steps that accept a params array (like
"inject") to inspect the given type parameter to determine if it is an
array/list/collection and if so, recognize that the parameter being passed is
an array. An extra bool parameter could then be passed to the Bytecode.AddStep
method to specify whether the parameter being passed should be "flattened",
which should only be the case if the parameter passed to the step (like
"inject") was _not_ an array/list/collection - i.e., it was a params array.
This same solution could also address the issue with
GraphTraversalSource.WithSideEffect, where if an array parameter is passed, the
Bytecode.AddSource method incorrectly flattens the array elements into separate
parameters, which causes the server to throw an exception because its seeing
"withSideEffect" being invoked with more parameters than expected.
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