feat(dotnet): make the .NET binding work on macOS and Linux via the pure-C shimtion

.github/workflows/ci_linux.yml

@@ -68,7 +68,28 @@ jobs:
       - name: Run all tests
         run: bazelisk test --verbose_failures //...
 
-      # 🔟 Upload test logs
+      # 🔟 .NET binding — build and test the managed wrapper against the shared
+      #    library just built. Pinned to 8.0.x because that is what DDS_Core
+      #    targets; the test project's RollForward only matters where no 8.0
+      #    runtime exists, which is not the case here.
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with: 
+          dotnet-version: "8.0.x"
+
+      # bazel-bin is a configuration-dependent convenience symlink, so ask Bazel
+      # for it rather than hardcoding a path that a different --config would move.
+      - name: Test .NET binding
+        run: |
+          bazelisk build --verbose_failures //jni:dds_shared
+          export DDS_LIBRARY_PATH="$(bazelisk info bazel-bin)/jni/libdds.so"
+          test -f "$DDS_LIBRARY_PATH" || { echo "native library not found at $DDS_LIBRARY_PATH"; exit 1; }
+          # Both configurations: ThrowIfError is unconditional, so a regression to
+          # [Conditional("DEBUG")] only surfaces in Release. See dotnet-binding.md.
+          dotnet test dotnet/DDS_Core.Tests/ --verbosity normal
+          dotnet test dotnet/DDS_Core.Tests/ -c Release --verbosity normal
+
+      # 11 Upload test logs
       - name: Upload test logs - Linux
         if: always()
         uses: actions/upload-artifact@v6

.github/workflows/ci_macos.yml

@@ -49,6 +49,28 @@ jobs:
       - name: Run all tests
         run: bazelisk test --verbose_failures //...
 
+      # .NET binding — this job is the only CI coverage of the AArch64 ABI, which
+      # is what the managed struct-layout tests exist to guard: a layout mismatch
+      # there corrupts results silently rather than throwing. Linux covers SysV
+      # x86-64 and Windows covers Win64, so all three ABIs are exercised.
+      # Pinned to 8.0.x to match what DDS_Core targets.
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "8.0.x"
+
+      # bazel-bin is a configuration-dependent convenience symlink, so ask Bazel
+      # for it rather than hardcoding a path that a different --config would move.
+      - name: Test .NET binding
+        run: |
+          bazelisk build --verbose_failures //jni:dds_shared
+          export DDS_LIBRARY_PATH="$(bazelisk info bazel-bin)/jni/libdds.dylib"
+          test -f "$DDS_LIBRARY_PATH" || { echo "native library not found at $DDS_LIBRARY_PATH"; exit 1; }
+          # Both configurations: ThrowIfError is unconditional, so a regression to
+          # [Conditional("DEBUG")] only surfaces in Release. See dotnet-binding.md.
+          dotnet test dotnet/DDS_Core.Tests/ --verbosity normal
+          dotnet test dotnet/DDS_Core.Tests/ -c Release --verbosity normal
+
       # Upload test logs
       - name: Upload test logs - macOS
         if: always()

.github/workflows/ci_windows.yml

@@ -56,6 +56,37 @@ jobs:
       - name: Run all tests
         run: bazelisk test --config=opt --verbose_failures //...
 
+      # .NET binding — this is the platform the shim retarget can regress.
+      # Windows was previously the only place the binding worked, via
+      # dds_native.dll and dds_api.hpp's dds_* symbols; it now binds dds_c_*
+      # in the Bazel-built dds.dll, a path no other test covers (the JNI smoke
+      # tests and export_set_test are target_compatible_with-excluded here).
+      # Pinned to 8.0.x to match what DDS_Core targets.
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: "8.0.x"
+
+      # bazel-bin is a configuration-dependent convenience symlink, so ask Bazel
+      # for it rather than hardcoding a path that a different --config would move.
+      - name: Test .NET binding
+        shell: pwsh
+        run: |
+          bazelisk build --verbose_failures //jni:dds_shared
+          if ($LASTEXITCODE -ne 0) { exit 1 }
+          $binDir = bazelisk info bazel-bin
+          $env:DDS_LIBRARY_PATH = Join-Path $binDir "jni\dds.dll"
+          if (-not (Test-Path $env:DDS_LIBRARY_PATH)) {
+            Write-Host "native library not found at $env:DDS_LIBRARY_PATH"
+            exit 1
+          }
+          # Both configurations: ThrowIfError is unconditional, so a regression to
+          # [Conditional("DEBUG")] only surfaces in Release. See dotnet-binding.md.
+          dotnet test dotnet/DDS_Core.Tests/ --verbosity normal
+          if ($LASTEXITCODE -ne 0) { exit 1 }
+          dotnet test dotnet/DDS_Core.Tests/ -c Release --verbosity normal
+          if ($LASTEXITCODE -ne 0) { exit 1 }
+
       # Upload test logs
       - name: Upload test logs - Windows
         if: always()

docs/dotnet_interface.md

@@ -9,9 +9,16 @@ The library exposes the full DDS functionality through idiomatic `.Net` structur
 
 The goal is to provide a stable, fast, and fully documented .NET interface to the DDS engine.
 
+It runs on **macOS, Linux, and Windows** from the same assembly — see
+[Building and loading the native library](#building-and-loading-the-native-library).
+The bindings mirror how the other language bindings work; see
+[jni_interface.md](jni_interface.md), [python_interface.md](python_interface.md),
+and [wasm_build.md](wasm_build.md).
+
 ---
 
 ## Table of Contents
+0. [Building and loading the native library](#building-and-loading-the-native-library)
 1. [Introduction](#introduction)
 2. [Legacy vs. Modern DDS API](#legacy-vs-modern-dds-api)
 3. [Basic Usage](#basic-usage)
@@ -39,6 +46,65 @@ The goal is to provide a stable, fast, and fully documented .NET interface to th
 
 ---
 
+# Building and loading the native library
+
+`DDS_Core` is a managed wrapper; the solver itself lives in one self-contained
+native library built by Bazel:
+
+```bash
+bazel build //jni:dds_shared
+```
+
+| OS      | Artifact       | Location         |
+| ------- | -------------- | ---------------- |
+| Linux   | `libdds.so`    | `bazel-bin/jni/` |
+| macOS   | `libdds.dylib` | `bazel-bin/jni/` |
+| Windows | `dds.dll`      | `bazel-bin/jni/` |
+
+Despite living under `//jni`, this is the shared native artifact for every
+binding — the JVM one uses it too.
+
+## Finding the library at runtime
+
+The binding imports the library under the single name **`dds`**; .NET's probing
+supplies the `lib` prefix and the per-OS extension, so one name resolves all
+three artifacts above. There are two ways to point it at a library:
+
+- **Default probing** — place the library where the runtime already looks (next
+  to the application, or under `runtimes/<rid>/native/` in a package). No
+  configuration needed.
+- **`DDS_LIBRARY_PATH`** — set this environment variable to the *full path* of a
+  library file to override probing. This is the counterpart of the JVM binding's
+  `-Ddds.library.path`, and is how the tests bind against a freshly-built
+  library:
+
+  ```bash
+  export DDS_LIBRARY_PATH="$(bazel info bazel-bin)/jni/libdds.dylib"
+  dotnet test dotnet/DDS_Core.Tests/
+  ```
+
+  Use `bazel info bazel-bin` rather than the `bazel-bin` symlink: that symlink is
+  configuration-dependent and moves when you build with a different `--config`.
+  If the variable is set but the library cannot be loaded, the error names the
+  path you gave rather than reporting a missing entry point later.
+
+## Which native symbols are used
+
+The modern context API binds the pure-C shim (`dds_c_*`, from
+`library/src/api/dds_c_api.h`); the legacy flat API binds `dll.h` directly. The
+reference-taking `dds_*` functions in `dds_api.hpp` are deliberately **not**
+used — they are not exported on Linux or macOS, and binding them is what
+previously made this wrapper Windows-only.
+
+## Requirements
+
+.NET 8.0 or later (`.NET Framework` is not supported). If you build the test
+project on a machine that has only a newer major runtime installed, note it sets
+`<RollForward>Major</RollForward>` so it still runs; the library itself targets
+`net8.0`.
+
+---
+
 # Introduction
 
 `DDS_Core` provides a managed .NET interface to the DDS engine.  

docs/jni_interface.md

@@ -72,12 +72,16 @@ and ctypes can all bind to:
 
 - The solver handle is opaque: `typedef void* DDS_C_SOLVER_CTX`.
 - Every struct is passed by pointer; no non-POD C++ type crosses the boundary.
-
-Shim entry points: `dds_c_create_solvercontext_default`,
-`dds_c_destroy_solvercontext`, `dds_c_solve_board`, `dds_c_calc_dd_table`,
-`dds_c_calc_par`. The flat legacy C API from `dll.h` (`SolveBoard`,
-`CalcDDtable`, `GetDDSInfo`, `ErrorMessage`, …) is exported unchanged and is
-also callable from FFM.
+  `SolverConfig` is decomposed into scalar arguments and `TTKind` crosses as an
+  `int`, so nothing is passed by value either.
+
+The shim covers the modern API's full surface: context lifecycle (default and
+config-based creation, destroy), `dds_c_solve_board`, `dds_c_calc_dd_table` and
+its `_pbn` twin, `dds_c_calc_par`, transposition-table configure/resize/clear,
+both resets, and the logging passthroughs. The Java bindings here use a subset;
+the .NET binding uses all of it ([dotnet_interface.md](dotnet_interface.md)).
+The flat legacy C API from `dll.h` (`SolveBoard`, `CalcDDtable`, `GetDDSInfo`,
+`ErrorMessage`, …) is exported unchanged and is also callable from FFM.
 
 ## Using the FFM bindings
 

dotnet/DDS_Core.Tests/ContextLifecycleTests.cs

@@ -0,0 +1,160 @@
+using DDS_Core;
+
+namespace DDS_Core.Tests;
+
+/// <summary>
+/// Covers the context-management entry points added to the C shim by this work:
+/// config-based construction, TT configuration, the resets, logging, and
+/// SafeHandle-driven disposal. Between these and <see cref="SmokeTests"/>, every
+/// one of the fourteen retargeted P/Invokes is exercised — so a missing
+/// <c>EntryPoint</c> fails here rather than in a consumer.
+/// </summary>
+public class ContextLifecycleTests
+{
+    [Theory]
+    [InlineData(TTKind.Small)]
+    [InlineData(TTKind.Large)]
+    public void ConstructedFromConfig_SolvesReferenceDeal(TTKind kind)
+    {
+        // Exercises dds_c_create_solvercontext, whose SolverConfig is unpacked
+        // into scalars at the ABI boundary.
+        using var ctx = new SolverContext(new SolverConfig(kind, 0, 0));
+
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks fut);
+
+        Assert.Equal(TestDeals.ExpectedTricks, fut.Score[0]);
+    }
+
+    /// <summary>
+    /// A successfully created context must hold a valid native handle. The
+    /// creation guard cannot test the reference for null — the SafeHandle
+    /// marshaller never returns one — so it tests IsInvalid, and this pins that
+    /// the successful path actually produces a live pointer rather than
+    /// IntPtr.Zero silently sailing through.
+    /// </summary>
+    [Theory]
+    [InlineData(TTKind.Small)]
+    [InlineData(TTKind.Large)]
+    public void Construction_YieldsValidHandle(TTKind kind)
+    {
+        using var fromConfig = new SolverContext(new SolverConfig(kind, 0, 0));
+        Assert.False(fromConfig.Handle.IsInvalid);
+
+        using var fromDefault = new SolverContext();
+        Assert.False(fromDefault.Handle.IsInvalid);
+    }
+
+    /// <summary>
+    /// Failures must throw at the public surface in every build configuration,
+    /// not only in DEBUG. `solutions = 4` is out of range and the solver returns
+    /// RETURN_SOLNS_WRONG_HI (-9); if ThrowIfError is ever made conditional
+    /// again, this test fails in Release.
+    /// </summary>
+    [Fact]
+    public void SolveBoard_WithInvalidSolutions_Throws()
+    {
+        using var ctx = new SolverContext();
+
+        Assert.Throws<InvalidOperationException>(
+            () => ctx.SolveBoard(TestDeals.Reference(), -1, 4, 1, out FutureTricks _));
+    }
+
+    [Fact]
+    public void TtReconfiguration_LeavesContextUsable()
+    {
+        using var ctx = new SolverContext();
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks _);
+
+        ctx.ConfigureTT(TTKind.Small, 1, 2);
+        ctx.ResizeTT(1, 2);
+        ctx.ClearTT();
+
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks fut);
+        Assert.Equal(TestDeals.ExpectedTricks, fut.Score[0]);
+    }
+
+    [Fact]
+    public void Resets_LeaveContextUsable()
+    {
+        using var ctx = new SolverContext();
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks _);
+
+        ctx.ResetForSolve();
+        ctx.ResetBestMovesLite();
+
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks fut);
+        Assert.Equal(TestDeals.ExpectedTricks, fut.Score[0]);
+    }
+
+    /// <summary>
+    /// A Small-TT context survives ClearTT() followed by ResetForSolve() and
+    /// still solves. ClearTT() disposes the transposition table, so the
+    /// following solve rebuilds one lazily from the context's configuration.
+    /// This exercises the managed TT-lifecycle path; the native
+    /// TransTableS::reset_memory() guard is covered by
+    /// //library/tests/trans_table:trans_table.
+    /// </summary>
+    [Fact]
+    public void SmallTt_ClearThenResetForSolve_StillSolves()
+    {
+        using var ctx = new SolverContext();
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks _);
+
+        ctx.ConfigureTT(TTKind.Small, 1, 2);
+        ctx.ClearTT();
+        ctx.ResetForSolve();
+
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks fut);
+        Assert.Equal(TestDeals.ExpectedTricks, fut.Score[0]);
+    }
+
+    [Fact]
+    public void Logging_DoesNotDisturbSolving()
+    {
+        using var ctx = new SolverContext();
+
+        ctx.LogAppend("DDS_Core.Tests");
+        ctx.LogAppend(string.Empty);
+        ctx.LogClear();
+
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks fut);
+        Assert.Equal(TestDeals.ExpectedTricks, fut.Score[0]);
+    }
+
+    /// <summary>
+    /// Disposal must release the native context through SafeHandle without
+    /// faulting, and must be safe to repeat.
+    /// </summary>
+    [Fact]
+    public void Dispose_ReleasesHandleAndIsIdempotent()
+    {
+        var ctx = new SolverContext();
+        ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks _);
+
+        ctx.Dispose();
+        ctx.Dispose();
+
+        Assert.True(ctx.Handle.IsClosed || ctx.Handle.IsInvalid);
+    }
+
+    /// <summary>
+    /// Contexts are single-threaded, so concurrent use means one context per
+    /// thread. This is the arrangement the docs prescribe; if it regressed,
+    /// multi-threaded consumers would corrupt results rather than fail loudly.
+    /// </summary>
+    [Fact]
+    public void OneContextPerThread_SolvesConcurrently()
+    {
+        const int threads = 4;
+        var results = new int[threads];
+
+        Parallel.For(0, threads, i =>
+        {
+            using var ctx = new SolverContext();
+            ctx.SolveBoard(TestDeals.Reference(), -1, 1, 1, out FutureTricks fut);
+            results[i] = fut.Score[0];
+        });
+
+        Assert.All(results, r => Assert.Equal(TestDeals.ExpectedTricks, r));
+    }
+}