Use the configured HandleNullPropagationOption

[DanielBertocci]

Fix unexpected behavior when HandleNullPropagationOption is configured in ODataQuerySettings

Context

Although a developer can set the value of context.QuerySettings.HandleNullPropagationOption using

[EnableQuery(HandleNullPropagation = HandleNullPropagationOption.False)]

or using DI with ODataQuerySettings

services.AddSingleton(new ODataQuerySettings {
    HandleNullPropagation = HandleNullPropagationOption.False
});

In the current implementation, when execution enters SelectExpandBinder the setting is sometimes forced to true, regardless of the developer's configuration.

This is my first time contributing to this library, although I have used it extensively. I tried to trace the history of this behavior but couldn't find a clear reason for forcing the option. The oldest commit I found that introduced this change is Commit: Merge routing, formatter, query into one from five years ago, and the behavior appears to have been retained through subsequent refactorings.

@xuzhg — you authored that commit and have recently worked on this file, so perhaps you can help if I've missed something.

All the tests are green, and I don't think if it is valuable to introduce a new one to validate this behavior.

Current workaround (project side)

I register a custom FilterBinder that forces the HandleNullPropagation setting:

class CustomODataFilterBinder : FilterBinder
{
    public override Expression Bind(QueryNode node, QueryBinderContext context)
    {
        context.QuerySettings.HandleNullPropagation = HandleNullPropagationOption.False;
        return base.Bind(node, context);
    }
}

How I encountered this issue

I have a project that uses Entity Framework with PostgreSQL. I needed to build OData queries involving many-to-many relationships, for example:

1. nodes?$expand=children($filter=children/$count gt 0)
2. customers?$expand=orders($filter=products/$count eq 0)
3. customers?$expand=orders($filter=products/any(c: c/name eq 'Sample'))

In case 1, even though HandleNullPropagationOption was forced to true, the expression that joined the same table did not cause issues. However, when joining different tables (cases 2 and 3), the generated expression included null checks that Entity Framework could not translate.

[DanielBertocci]

@microsoft-github-policy-service agree

[WanjohiSammy]

/AzurePipelines run

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[WanjohiSammy]

Why not pass the HandleNullPropagation in the caller. For example:

• In SelectExpandBinder, you can pass as follows:

  // rest of code ..
  QueryBinderContext subContext = CreateSubContext(context, computeClause, clrElementType, settings.HandleNullPropagation);
  // rest of code ...

[DanielBertocci]

Hi @WanjohiSammy. The reason why I didn't pass HandleNullPropagation in the caller is because CreateSubContext originally clones the settings:

ODataQuerySettings newSettings = new ODataQuerySettings();
newSettings.CopyFrom(context.QuerySettings);

The CopyFrom method does copy the HandleNullPropagation value:

internal void CopyFrom(ODataQuerySettings settings)
{
    // ...
    HandleNullPropagation = settings.HandleNullPropagation;
    // ...
}

I kept this approach because the original code also cloned context.QuerySettings, and I wanted to preserve that behavior unless there's a specific reason to move to the overload that takes HandleNullPropagation directly. If using the explicit overload is preferred for clarity, I can switch to that as well.

[WanjohiSammy]

@DanielBertocci Could you add some tests for this fix.