feat(mapping): MapToSqlTableValuedParameter attribute and empty/struct TVP fixes

[dtraft]

Posted by: Claude Code (Claude Fable 5.1) | 2026-09-08

TL;DR

Adds MapToSqlTableValuedParameterAttribute so a collection property maps to a SQL Server table-valued parameter on write (and, with the shared mapper change, to an additional result set on read), and fixes two TVP edge cases in AddSqlTableValuedParameter.

Changes

• SqlMapAttributes.cs: new MapToSqlTableValuedParameterAttribute(parameterName, typeName) : CollectionMapAttributeBase. The emitted expression calls AddSqlTableValuedParameter<TElement> and sets SqlParameter.TypeName. Value-type collections (ImmutableArray<T>) are explicitly converted to IEnumerable<T> (Expression.Call requires reference-assignability), and a default (uninitialized) ImmutableArray<T> -- which throws on enumeration -- is normalized to Empty.
• SqlParameterCollectionExtensions.cs: both AddSqlTableValuedParameter overloads send DBNull.Value for an empty collection (an empty IEnumerable<SqlDataRecord> cannot supply TDS metadata and is rejected by the driver; SQL Server treats a null TVP as an empty table). The columnList overload previously had no empty guard at all.
• Tests (new): test/CollectionMapWriteTests.cs (populated/empty/default collections through both overloads and through CreateInputParameters, for List<T> and ImmutableArray<T>) and test/CollectionMapReadTests.cs (multi-result-set hydration, declaration order, empty vs missing result set, missing record, attribute-less model, ImmutableArray<T> read).

Testing

ArgentSea.Sql.Test: 116 passed, 0 failed (101 pre-existing + 15 new). Exercised live against SQL Server by a downstream Orleans grain whose state carries two TVP-mapped collections.

Dependencies

Depends on argentsea/shared (CollectionMapAttributeBase and the read-side handler). Second of four: shared -> sql -> Orleans -> Orleans.Sql.

Related PRs (merge in this order)

1. feat(mapping): collection-mapped properties with multi-result-set read handler shared#4
2. feat(mapping): MapToSqlTableValuedParameter attribute and empty/struct TVP fixes #2
3. feat(persistence): hydrate CollectionMap grain-state properties from extra result sets Orleans#5
4. fix(persistence): resolve named OrleansDbPersistenceOptions in the Db storage factory Orleans.Sql#3