Evaluatable expressions with parameters are no more pre-evaluated

[dbakuntsev]

Tried with the git clone https://github.com/nhibernate/nhibernate-core.git branch.

The following mock-up code will not work:

Guid guid = Guid.Parse("2D7E6EB3-BD08-4A40-A4E7-5150F7895821");
session.Query<Entity>().Where(x => x.TextField.Contains($"VALUE {guid}"))

That is, NhRelinqQueryParser.PreTransform() instead of evaluating String.Format to its final form "VALUE 2D7E6EB3-BD08-4A40-A4E7-5150F7895821" will stop short and will yield Format("VALUE {0}", Convert("2D7E6EB3-BD08-4A40-A4E7-5150F7895821")) instead. Naturally, that will not be translated to any meaningful SQL later on and will result in an exception System.NotSupportedException: System.String Format(System.String, System.Object, System.Object).

A trivial workaround exists:

Guid guid = Guid.Parse("2D7E6EB3-BD08-4A40-A4E7-5150F7895821");
session.Query<Entity>().Where(x => x.TextField.Contains($"VALUE {guid.ToString()}"))

But it occurs to me that this is a bug, as the workaround shouldn't be required.

Furthermore, it is not obvious what's going on from looking at the final exception (so the workaround may be implemented).

[bahusoid]

That is, NhRelinqQueryParser.PreTransform() instead of evaluating String.Format to its final form "VALUE 2D7E6EB3-BD08-4A40-A4E7-5150F7895821" will stop short and will yield Format("VALUE {0}", Convert("2D7E6EB3-BD08-4A40-A4E7-5150F7895821")) instead.

Maybe I'm wrong but seems should be reported to re-linq project.

A trivial workaround exists...

Just a suggestion. Avoid any possible in-code calculations from LINQ query. So in you case you can move value calculation out of LINQ query:

Guid guid = Guid.Parse("2D7E6EB3-BD08-4A40-A4E7-5150F7895821");
var value = $"VALUE {guid}";
session.Query<Entity>().Where(x => x.TextField.Contains(value))

That would simplify query parsing and might avoid you to encounter many unexpected behaviors.

[dbakuntsev]

Maybe I'm wrong but seems should be reported to re-linq project.

I thought so, too, initially. But NHibernate.Linq.Visitors.NhEvaluatableExpressionFilter may be a better candidate for the bugfix.

[maca88]

This is a regression from #2335, where NhEvaluatableExpressionFilter.IsEvaluatableUnary returns false in this case as guid is detected as a variable. I will make a fix, but most likely tomorrow.

[dbakuntsev]

Maybe related:

Guid[] guids = { Guid.Parse("07B430F0-C50F-4D8D-9206-073240B602E2") };
session.Query<Entity>().Where(x => guids.Length == 0 || guids.Contains(x.GuidField));

This causes a cryptic System.NotSupportedException: : ( : p1 ). Specifically, the heartburn is due to guids.Length == 0 as without it the expression executes just fine. A possible workaround is to use !guids.Any() expression instead of guids.Length == 0.

[maca88]

Maybe related

It is related. I made a fix for both queries in #2462.