TdsParserStateObject.ResetSnapshot() Debug.Assert failing

[paulmedynski]

Failure is here:

    /home/paul/dev/SqlClient/dev/paul/app-context-switch-test-helper/src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStateObject.cs(3441): error TESTERROR:
      Microsoft.Data.SqlClient.ManualTesting.Tests.DataReaderTest.CanReadXmlData (354ms): Error Message: Microsoft.VisualSt
      udio.TestPlatform.TestHost.DebugAssertException : Method Debug.Fail failed with 'snapshot._storage == null
      ', and was translated to Microsoft.VisualStudio.TestPlatform.TestHost.DebugAssertException to avoid terminating the p
      rocess hosting the test.

Here's the code:

            if (_snapshot != null)
            {
                StateSnapshot snapshot = _snapshot;
                _snapshot = null;
                Debug.Assert(snapshot._storage == null);
                snapshot.Clear();
                Interlocked.CompareExchange(ref _cachedSnapshot, snapshot, null);
            }

@Wraith2 I'm not sure what the intention of the Assert() is.

[paulmedynski]

There are several failing Asserts() that I have had to comment out, identified by TODO(GH-3385) once #3371 hits main.

[Wraith2]

Can you identify a specific test or tests that cause asserts? Since running tests in debug mode in VS still ignores all conditional attributes you'll find that running everything causes a lot of failures and blocking assert messageboxes.

In the original implementation the asserts around the snapshot storage were setup so that I could see storage was ever used in a way that I wasn't expecting. After reworking the state transfer mechanism in #3337 and #3329 the guarantees around snapshot Clear() in particular have softened because the code is a little more optimistic about buffer storage that will sometimes not be needed. It's fine to delete that one.
Any others I'd want to dig into a little before removing.

[paulmedynski]

All 3 of the commented-out Debug.Assert() statements are causing this test to fail:

Microsoft.Data.SqlClient.ManualTesting.Tests.DataReaderTest.CanReadXmlData

You can run all of the DataReader tests on the command line like this after uncommenting them one at a time:

.../ManualTests$ dotnet build
.../ManualTests$ dotnet test --no-build -f net9.0 --filter DataReaderTest