Add primary keys to procedural views in C# (#5246)

# Description of Changes

Adds primary keys to procedural views in C#. See for #5111 for the
equivalent feature in rust and C# as well as a more detailed
description.

# API and ABI breaking changes

None

# Expected complexity level and risk

3

# Testing

- [x] Equivalent tests as were added in #5111 for rust and typescript

Author: joshua-spacetime

crates/bindings-csharp/BSATN.Codegen/Type.cs

@@ -455,6 +455,56 @@ public enum TypeKind
     Sum,
 }
 
+public static class SpacetimeDbFieldDiscovery
+{
+    private static readonly string[] SpacetimeDbRowAttributeNames =
+    [
+        "SpacetimeDB.TypeAttribute",
+        "SpacetimeDB.TableAttribute",
+    ];
+
+    public static IEnumerable<IFieldSymbol> GetFieldsDeclaredInAnnotatedPartial(
+        TypeDeclarationSyntax typeSyntax,
+        INamedTypeSymbol type
+    ) =>
+        typeSyntax
+            .Members.OfType<FieldDeclarationSyntax>()
+            .SelectMany(f => f.Declaration.Variables)
+            .Select(v => type.GetMembers(v.Identifier.Text).OfType<IFieldSymbol>().Single())
+            .Where(f => !f.IsStatic);
+
+    public static IFieldSymbol? FindSpacetimeDbField(ITypeSymbol rowType, string fieldName)
+    {
+        if (rowType is not INamedTypeSymbol namedRowType)
+        {
+            return null;
+        }
+
+        foreach (var typeSyntax in GetAnnotatedPartialDeclarations(namedRowType))
+        {
+            var field = GetFieldsDeclaredInAnnotatedPartial(typeSyntax, namedRowType)
+                .FirstOrDefault(field => field.Name == fieldName);
+            if (field is not null)
+            {
+                return field;
+            }
+        }
+
+        return null;
+    }
+
+    private static IEnumerable<TypeDeclarationSyntax> GetAnnotatedPartialDeclarations(
+        INamedTypeSymbol type
+    ) =>
+        type.GetAttributes()
+            .Where(attr => SpacetimeDbRowAttributeNames.Contains(attr.AttributeClass?.ToString()))
+            .Select(attr => attr.ApplicationSyntaxReference?.GetSyntax())
+            .OfType<AttributeSyntax>()
+            .Select(attr => attr.FirstAncestorOrSelf<TypeDeclarationSyntax>())
+            .OfType<TypeDeclarationSyntax>()
+            .Distinct();
+}
+
 public abstract record BaseTypeDeclaration<M>
     where M : MemberDeclaration, IEquatable<M>
 {
@@ -498,11 +548,10 @@ public BaseTypeDeclaration(GeneratorAttributeSyntaxContext context, DiagReporter
         //
         // To achieve this, we need to walk over the annotated type syntax node, collect the field names,
         // and look up the resolved field symbols only for those fields.
-        var fields = typeSyntax
-            .Members.OfType<FieldDeclarationSyntax>()
-            .SelectMany(f => f.Declaration.Variables)
-            .Select(v => type.GetMembers(v.Identifier.Text).OfType<IFieldSymbol>().Single())
-            .Where(f => !f.IsStatic);
+        var fields = SpacetimeDbFieldDiscovery.GetFieldsDeclaredInAnnotatedPartial(
+            typeSyntax,
+            type
+        );
 
         // Check if type implements generic `SpacetimeDB.TaggedEnum<Variants>` and, if so, extract the `Variants` type.
         if (type.BaseType?.OriginalDefinition.ToString() == "SpacetimeDB.TaggedEnum<Variants>")

crates/bindings-csharp/Codegen.Tests/fixtures/diag/Lib.cs

@@ -498,10 +498,42 @@ public partial struct Player
     public Identity Identity;
 }
 
+[SpacetimeDB.Type]
+public partial struct ViewPrimaryKeyRenamedRow
+{
+    public Identity RenamedIdentity;
+}
+
+[SpacetimeDB.Type]
+public partial class ViewPrimaryKeyPartialRow
+{
+    public Identity DeclaredIdentity;
+}
+
+public partial class ViewPrimaryKeyPartialRow
+{
+    public Identity ExtraPartialIdentity;
+}
+
+[SpacetimeDB.Type]
+public partial struct NonEquatableViewPrimaryKey
+{
+    public uint Value;
+}
+
+[SpacetimeDB.Type]
+public partial struct NonEquatableViewPrimaryKeyRow
+{
+    public NonEquatableViewPrimaryKey Identity;
+}
+
 public struct NotSpacetimeType { }
 
 public partial class Module
 {
+    [SpacetimeDB.Settings]
+    public const CaseConversionPolicy CASE_CONVERSION_POLICY = CaseConversionPolicy.SnakeCase;
+
 #pragma warning disable STDB_UNSTABLE // Enable ClientVisibilityFilter
 
     // Invalid: not public static readonly
@@ -592,6 +624,54 @@ ViewContext ctx
         return ctx.Db.TestIndexIssues.TestUnexpectedColumns.Filter(0);
     }
 
+    // Invalid: PrimaryKey must refer to a field in the returned row type.
+    [SpacetimeDB.View(
+        Accessor = "view_primary_key_missing_column",
+        Public = true,
+        PrimaryKey = "MissingIdentity"
+    )]
+    public static List<Player> ViewPrimaryKeyMissingColumn(ViewContext ctx)
+    {
+        return new List<Player>();
+    }
+
+    // Invalid: PrimaryKey must use the C# source field name, not the canonicalized name.
+    [SpacetimeDB.View(
+        Accessor = "view_primary_key_uses_wrong_source_name",
+        Public = true,
+        PrimaryKey = "renamed_identity"
+    )]
+    public static List<ViewPrimaryKeyRenamedRow> ViewPrimaryKeyUsesWrongSourceName(ViewContext ctx)
+    {
+        return new List<ViewPrimaryKeyRenamedRow>();
+    }
+
+    // Invalid: PrimaryKey must refer to a field declared in the SpacetimeDB.Type partial.
+    [SpacetimeDB.View(
+        Accessor = "view_primary_key_uses_non_bsatn_partial_field",
+        Public = true,
+        PrimaryKey = "ExtraPartialIdentity"
+    )]
+    public static List<ViewPrimaryKeyPartialRow> ViewPrimaryKeyUsesNonBsatnPartialField(
+        ViewContext ctx
+    )
+    {
+        return new List<ViewPrimaryKeyPartialRow>();
+    }
+
+    // Invalid: PrimaryKey column type must match table primary-key validation.
+    [SpacetimeDB.View(
+        Accessor = "view_primary_key_non_equatable_column",
+        Public = true,
+        PrimaryKey = "Identity"
+    )]
+    public static List<NonEquatableViewPrimaryKeyRow> ViewPrimaryKeyNonEquatableColumn(
+        ViewContext ctx
+    )
+    {
+        return new List<NonEquatableViewPrimaryKeyRow>();
+    }
+
     // Invalid: Returns type that is not a SpacetimeType
     [SpacetimeDB.View(Accessor = "view_def_returns_not_a_spacetime_type", Public = true)]
     public static NotSpacetimeType? ViewDefReturnsNotASpacetimeType(AnonymousViewContext ctx)