[alaricd]

Summary

Initialize SpannerParameter.ParameterName to string.Empty and normalize null assignments back to the empty string. Add regression coverage for both cases.

Resolves #16043.

Microsoft contract

Microsoft documents the default value of DbParameter.ParameterName as an empty string: https://learn.microsoft.com/dotnet/api/system.data.common.dbparameter.parametername

Compatibility

This changes the observable value from null to empty for a new parameter and when null is assigned. Explicit non-null assignments are unchanged. Consumers that distinguish null from empty may observe the change; empty is the documented ADO.NET default and avoids null propagation through provider code.

Validation

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 — 2,833 passed, 0 failed.

Discovery

Found using pengdows.AdoNetApiTest.conformance.

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[gemini-code-assist]

Code Review

This pull request initializes the ParameterName property of SpannerParameter to string.Empty by default and adds a corresponding unit test. The feedback highlights that setting ParameterName to null should also return string.Empty to comply with the ADO.NET specification, and suggests using a backing field to handle null coercion.

[gemini-code-assist]

According to the ADO.NET specification for DbParameter.ParameterName, setting the property to null should also result in it returning an empty string (string.Empty). With an auto-implemented property, setting ParameterName to null will store and return null, which violates this contract and could lead to NullReferenceExceptions elsewhere. Consider using a backing field to coerce null values to string.Empty.

        private string _parameterName = string.Empty;
        public override string ParameterName
        {
            get => _parameterName;
            set => _parameterName = value ?? string.Empty;
        }