C# implementation of Transactions for Procedures (#3809)

# Description of Changes

Implements the C# equivalent of #3638

This implement uses inheritance, where abstract base classes (like
`ProcedureContextBase` in `ProcedureContext.cs`) store the core of the
implementation, and then generated wrappers (like `ProcedureContext` in
the generated FFI.cs file) inherit from them.

For error handling, we work like Rust's implementation of `Result<T,E>`
but we require `where E : Exception` because of how exceptions work in
C#. Transaction-level failures come back as a `TxOutcome` and user
errors should follow the `Result<T,E>` pattern. In this implementation,
we have `UnwrapOrThrow()` throws exceptions directly because of C#'s
error handling pattern.

Unlike the Rust implementation's direct `Result` propagation, we are
using an `AbortGuard` pattern (in `ProcedureContext.cs`) for exception
handling, which uses `IDisposable` for automatic cleanup.

Most changes should have fairly similar Rust-equivalents beyond that.
For module authors, the changes here allow for the transation logic to
work like:
```csharp
ctx.TryWithTx<ResultType, Exception>(tx => {
    // transaction logic
    return Result<ResultType, Exception>.Ok(result);
});
```
This change includes a number of tests added to the
`sdks/csharp/examples~/regression-tests/`'s `server` and `client` to
validate the behavior of the changes. `server` changes provide further
usage examples for module authors.

# API and ABI breaking changes

Should not be a breaking change

# Expected complexity level and risk

2

# Testing

- [x] Created Regression Tests that show transitions in procedures
working in various ways, all of which pass.

Author: rekhoff

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

@@ -53,6 +53,12 @@ public abstract record TypeUse(string Name, string BSATNName)
     /// <returns></returns>
     public static TypeUse Parse(ISymbol member, ITypeSymbol typeSymbol, DiagReporter diag)
     {
+        if (typeSymbol.SpecialType == SpecialType.System_Void)
+        {
+            // Treat void as equivalent to Unit type
+            return new ReferenceUse("SpacetimeDB.Unit", "SpacetimeDB.Unit.BSATN");
+        }
+
         var type = SymbolToName(typeSymbol);
         string typeInfo;
 

crates/bindings-csharp/BSATN.Runtime.Tests/BSATN.Runtime.Tests.csproj

@@ -1,5 +1,4 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
   <PropertyGroup>
     <IsPackable>false</IsPackable>
     <IsTestProject>true</IsTestProject>
@@ -20,7 +19,10 @@
 
   <ItemGroup>
     <ProjectReference Include="../BSATN.Runtime/BSATN.Runtime.csproj" />
-    <ProjectReference Include="../BSATN.Codegen/BSATN.Codegen.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+    <ProjectReference
+      Include="../BSATN.Codegen/BSATN.Codegen.csproj"
+      OutputItemType="Analyzer"
+      ReferenceOutputAssembly="false"
+    />
   </ItemGroup>
-
 </Project>

crates/bindings-csharp/BSATN.Runtime.Tests/Tests.cs

@@ -246,20 +246,12 @@ public BasicDataClass((int x, string y, int? z, string? w) data)
     }
 
     [Type]
-    public partial struct BasicDataStruct
+    public partial struct BasicDataStruct((int x, string y, int? z, string? w) data)
     {
-        public int X;
-        public string Y;
-        public int? Z;
-        public string? W;
-
-        public BasicDataStruct((int x, string y, int? z, string? w) data)
-        {
-            X = data.x;
-            Y = data.y;
-            Z = data.z;
-            W = data.w;
-        }
+        public int X = data.x;
+        public string Y = data.y;
+        public int? Z = data.z;
+        public string? W = data.w;
     }
 
     [Type]
@@ -315,12 +307,12 @@ public void Add(bool collides)
             }
         }
 
-        public double CollisionFraction
+        public readonly double CollisionFraction
         {
             get => (double)Collisions / (double)Comparisons;
         }
 
-        public void AssertCollisionsLessThan(double fraction)
+        public readonly void AssertCollisionsLessThan(double fraction)
         {
             Assert.True(
                 CollisionFraction < fraction,
@@ -626,18 +618,13 @@ public static void GeneratedNestedListRoundTrip()
         .Select(list => new ContainsNestedList(list));
 #pragma warning restore CS8620 // Argument cannot be used for parameter due to differences in the nullability of reference types.
 
-
     static readonly Gen<(ContainsNestedList e1, ContainsNestedList e2)> GenTwoContainsNestedList =
         Gen.Select(GenContainsNestedList, GenContainsNestedList, (e1, e2) => (e1, e2));
 
-    class EnumerableEqualityComparer<T> : EqualityComparer<IEnumerable<T>>
+    class EnumerableEqualityComparer<T>(EqualityComparer<T> equalityComparer)
+        : EqualityComparer<IEnumerable<T>>
     {
-        private readonly EqualityComparer<T> EqualityComparer;
-
-        public EnumerableEqualityComparer(EqualityComparer<T> equalityComparer)
-        {
-            EqualityComparer = equalityComparer;
-        }
+        private readonly EqualityComparer<T> EqualityComparer = equalityComparer;
 
         public override bool Equals(IEnumerable<T>? x, IEnumerable<T>? y) =>
             x == null ? y == null : (y == null ? false : x.SequenceEqual(y, EqualityComparer));

crates/bindings-csharp/BSATN.Runtime/BSATN.Runtime.csproj

@@ -1,5 +1,4 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
   <PropertyGroup>
     <AssemblyName>SpacetimeDB.BSATN.Runtime</AssemblyName>
     <Version>1.11.1</Version>
@@ -18,18 +17,25 @@
 
   <ItemGroup>
     <!-- We want to build BSATN.Codegen both to include it in our NuGet package but also we want it to transform [SpacetimeDB.Type] usages in BSATN.Runtime code itself. -->
-    <ProjectReference Include="../BSATN.Codegen/BSATN.Codegen.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+    <ProjectReference
+      Include="../BSATN.Codegen/BSATN.Codegen.csproj"
+      OutputItemType="Analyzer"
+      ReferenceOutputAssembly="false"
+    />
   </ItemGroup>
 
   <ItemGroup>
     <None Include="../Runtime/README.md" Pack="true" PackagePath="" />
     <!-- We want all users who depends on BSATN.Runtime to automatically get the Roslyn codegen component as well. -->
-    <None Include="../BSATN.Codegen/bin/$(Configuration)/netstandard2.0/SpacetimeDB.BSATN.Codegen.dll" Pack="true" PackagePath="analyzers/dotnet/cs" />
+    <None
+      Include="../BSATN.Codegen/bin/$(Configuration)/netstandard2.0/SpacetimeDB.BSATN.Codegen.dll"
+      Pack="true"
+      PackagePath="analyzers/dotnet/cs"
+    />
   </ItemGroup>
 
   <ItemGroup>
     <!-- dev-dependency to add internal C# classes and attributes not included in .NET Standard -->
     <PackageReference Include="PolySharp" Version="1.14.1" PrivateAssets="all" />
   </ItemGroup>
-
 </Project>

crates/bindings-csharp/BSATN.Runtime/BSATN/AlgebraicType.cs

@@ -6,17 +6,11 @@ public interface ITypeRegistrar
 }
 
 [SpacetimeDB.Type]
-public partial struct AggregateElement
+public partial struct AggregateElement(string name, AlgebraicType algebraicType)
 {
-    public string? Name;
+    public string? Name = name;
 
-    public AlgebraicType AlgebraicType;
-
-    public AggregateElement(string name, AlgebraicType algebraicType)
-    {
-        Name = name;
-        AlgebraicType = algebraicType;
-    }
+    public AlgebraicType AlgebraicType = algebraicType;
 }
 
 [SpacetimeDB.Type]