[jira] [Commented] (TINKERPOP-3029) Gremlin.Net: Traversal enumeration fails on .NET 8

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TINKERPOP-3029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17802254#comment-17802254 ] 

ASF GitHub Bot commented on TINKERPOP-3029:
-------------------------------------------

FlorianHockmann opened a new pull request, #2424:
URL: https://github.com/apache/tinkerpop/pull/2424

   https://issues.apache.org/jira/browse/TINKERPOP-3029
   
   `IEnumerable<T>.Current` has been changed in .NET 8. Before .NET 8, it simply returned `null` if `MoveNext()` wasn't called first. With .NET 8 however it throws an exception.
   Since this has apparently already been undefined behavior before, we should fix this irrespective of .NET 8:
   https://github.com/dotnet/runtime/issues/85243#issuecomment-1521085177
   
   The problem can be reproduced by executing the Gherkin tests with .NET without the change in `DefaultTraversal` (by changing the `TargetFramework` in `Gremlin.Net.IntegrationTest.csproj` to `net8.0`). .NET 8 needs to be installed for this of course.
   
   VOTE +1




> Gremlin.Net: Traversal enumeration fails on .NET 8
> --------------------------------------------------
>
>                 Key: TINKERPOP-3029
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-3029
>             Project: TinkerPop
>          Issue Type: Bug
>          Components: dotnet
>    Affects Versions: 3.5.8, 3.6.6, 3.7.1
>            Reporter: Florian Hockmann
>            Assignee: Florian Hockmann
>            Priority: Critical
>
> This has been reported by Eric Sites on the dev mailing list: [https://lists.apache.org/thread/snztwgk3s18h83mx8ql455hmx6ncl2r4]
> ----
> I am having a lot of issues using the Gremlin.Net driver version 3.7.1 with .Net 8.
> It is almost entirely unusable.
> Any request that uses an Iterator throws an exception ({{{}MoveNext{}}}, {{{}Next{}}}, {{{}Iterate{}}}).
> {{{}System.InvalidOperationException: Enumeration has not started. Call MoveNext{}}}.
> Tracked it down to a change in .Net 8 {{IEnumerable<T>.Current}} behavior. Here is an issue about this filed in dotnet runtime:
> [https://github.com/dotnet/runtime/issues/85243]
> New bad code:
> {code:java}
> var enumerator = saves.GetEnumerator();
> while (enumerator.Current == null) // <- Throws exception now
> {
>    if (!enumerator.MoveNext())
>       return list;
> }
> {code}
> Should be changed to something like this:
> {code:java}
> while (enumerator.MoveNext())
> {
>     var item = enumerator.Current;
> }
> {code}
> Here is an example of the issue in the Gremlin.Net code:
> [https://github.com/apache/tinkerpop/blob/e8b9532fc0ec811460e97ebf5e00b8b9ec9192ac/gremlin-dotnet/src/Gremlin.Net/Process/Traversal/DefaultTraversal.cs#L132]
> {code:java}
> private object? GetCurrent()
> {
>     // Use dynamic to object to prevent runtime dynamic conversion evaluation
>     return TraverserEnumerator.Current?.Object;
> }
> {code}



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