[alaricd]

Summary

Make SpannerCommand.Prepare throw InvalidOperationException when no connection is assigned or when its connection is closed. Keep preparation a no-op when the connection is open, as Spanner does not support precompiled queries. Add regression tests for both invalid states.

Resolves #16047.

Microsoft contract

Microsoft documents InvalidOperationException when IDbCommand.Prepare is called without a connection or with a closed connection: https://learn.microsoft.com/dotnet/api/system.data.idbcommand.prepare

Compatibility

Commands with an open connection retain the existing no-op preparation behavior. Calls that currently succeed without an open connection will now throw as documented; applications relying on preparing disconnected commands may observe this change.

Validation

Focused provider tests: dotnet test apis/Google.Cloud.Spanner.Data/Google.Cloud.Spanner.Data.Tests/Google.Cloud.Spanner.Data.Tests.csproj --no-restore -f net8.0 -p:NoWarn=CS8981%3BxUnit2004%3BxUnit2013 --filter FullyQualifiedName~Prepare — 2 passed, 0 failed.

Discovery

Found using pengdows.AdoNetApiTest.conformance.

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[gemini-code-assist]

Code Review

This pull request updates the Prepare method in SpannerCommand to throw an InvalidOperationException if the connection is unset or not open, and adds corresponding unit tests. The review feedback suggests caching the SpannerConnection property in a local variable before checking its state to ensure thread safety and avoid potential compiler warnings.

[gemini-code-assist]

To ensure thread safety and avoid potential compiler warnings (such as CS8602) when nullable reference types are enabled, it is recommended to cache the mutable SpannerConnection property in a local variable before performing the null check and accessing its State property.

            var connection = SpannerConnection;
            if (connection == null)
            {
                throw new InvalidOperationException("The Connection property has not been set.");
            }
            if (connection.State != ConnectionState.Open)
            {
                throw new InvalidOperationException("The connection is not open.");
            }