bytecodealliance · jsturtevant · Mar 7, 2025 · Mar 7, 2025
diff --git a/README.md b/README.md
@@ -232,7 +232,26 @@ By default the project will find all wit files and execute wit-bindgen against e
 </ItemGroup>
 ```
 
+### Passing additional wit-bindgen args
+
+[wit-bindgen](https://github.com/bytecodealliance/wit-bindgen/tree/main) for c# has some advanced settings that can be set by using `WitBindgenAddtionalArgs` property. A non-exhustive list of example args that might be useful are:
+
+- `--features <featurename>` - turn on [wit features](https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md#feature-gates)
+- `--with-wit-results` - use [wit Result types](https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md#wit-types) instead of generating exceptions
+- `--skip-support-files` - don't output files like `WasmImportLinkageAttribute`
+
+Example: 
+
+```xml
+<PropertyGroup>
+  <WitBindgenAddtionalArgs>--with-wit-results --features tls</WitBindgenAddtionalArgs>
+</PropertyGroup>
+```
+
+To learn about addtional args run  `wit-bindgen c-sharp -h`
+
 ### Referencing Wit Packages from OCI Registries
+
 Wit can be packaged into [OCI Artifacts](https://tag-runtime.cncf.io/wgs/wasm/deliverables/wasm-oci-artifact/) which can be pushed to OCI registries.  To import a WIT definition from an OCI registry specify the Registry on the `Wit` Element.  This will pull a WASM component binary that contains the WIT definition. wit-bindgen can use the binary format directly to generate the bindings. To view the WIT directly use [`wasm-tools component wit wit/wit.wasm`](https://github.com/bytecodealliance/wasm-tools).  
 
 ```xml

diff --git a/src/WitBindgen/build/BytecodeAlliance.Componentize.DotNet.WitBindgen.targets b/src/WitBindgen/build/BytecodeAlliance.Componentize.DotNet.WitBindgen.targets
@@ -1,6 +1,7 @@
 <Project>
     <PropertyGroup>
         <WitBindgenRuntime>native-aot</WitBindgenRuntime>
+        <WitBindgenAddtionalArgs></WitBindgenAddtionalArgs>
 
         <!-- Keep this block all in sync manually, since URLs can be arbitrary -->
         <WasiSdkVersion>24.0</WasiSdkVersion>
@@ -86,7 +87,7 @@
 
         <RemoveDir Directories="$(WitGeneratedFilesRoot)" />
         <MakeDir Directories="$(WitGeneratedFilesRoot)" />
-        <Exec Command="$(WitBindgenExe) c-sharp %(Wit.Identity) %(Wit.WitWorldArg) --runtime $(WitBindgenRuntime) --out-dir $(WitGeneratedFilesRoot)" />
+        <Exec Command="$(WitBindgenExe) c-sharp %(Wit.Identity) %(Wit.WitWorldArg) --runtime $(WitBindgenRuntime) $(WitBindgenAddtionalArgs) --out-dir $(WitGeneratedFilesRoot)" />
         <WriteLinesToFile File="$(WitGeneratedFilesRoot)lastbuild.txt" Lines="" Overwrite="true" />
 
         <ItemGroup>

diff --git a/test/WitBindgenTest/WitBindgenTest/CodeGenerationTest.cs b/test/WitBindgenTest/WitBindgenTest/CodeGenerationTest.cs
@@ -1,5 +1,7 @@
 using MyFuncsWorld;
 using ProducerWorld;
+using MyResultsWorld;
+using MyWitResultsWorld;
 using System;
 using Xunit;
 
@@ -33,4 +35,16 @@ public void CanSpecifyWorld()
     {
         Assert.NotNull((Func<int>)SomeStuffImpl.GetNumber);
     }
+
+    [Fact]
+    public void ShouldBeNormalResult()
+    {
+        Assert.NotNull((Func<float, float>)MyResultsWorldImpl.StringError);
+    }
+
+    [Fact]
+    public void ShouldBeNormalWitResult()
+    {
+        Assert.NotNull((Func<float, MyWitResultsWorld.Result<float, string>>)MyWitResultsWorldImpl.StringError);
+    }
 }
diff --git a/test/WitBindgenTest/WitBindgenTest/WitBindgenTest.csproj b/test/WitBindgenTest/WitBindgenTest/WitBindgenTest.csproj
@@ -20,6 +20,8 @@
 
   <ItemGroup>
     <ProjectReference Include="..\testapps\LibraryUsingWit\LibraryUsingWit.csproj" />
+    <ProjectReference Include="..\testapps\LibraryWithExceptions\LibraryWitExceptions.csproj" />
+    <ProjectReference Include="..\testapps\LibraryWithWitResultType\LibraryWithWitResultType.csproj" />
   </ItemGroup>
 
 </Project>
diff --git a/test/WitBindgenTest/testapps/LibraryWithExceptions/LibraryWitExceptions.csproj b/test/WitBindgenTest/testapps/LibraryWithExceptions/LibraryWitExceptions.csproj
@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <!-- Only needed when referencing the dependencies as projects. For package references, these are imported automatically. -->
+    <Import Project="..\..\..\..\src\WitBindgen\ImportInDev.proj" />
+
+    <PropertyGroup>
+        <TargetFramework>net9.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\..\..\..\src\WitBindgen\WitBindgen.csproj" />
+      <PackageReference Include="runtime.$(NETCoreSdkPortableRuntimeIdentifier).Microsoft.DotNet.ILCompiler.LLVM"/>
+    </ItemGroup>
+
+    <ItemGroup>
+      <Wit Update="result.wit" />
+    </ItemGroup>
+
+</Project>
diff --git a/test/WitBindgenTest/testapps/LibraryWithExceptions/Result.cs b/test/WitBindgenTest/testapps/LibraryWithExceptions/Result.cs
@@ -0,0 +1,9 @@
+using MyResultsWorld;
+
+public class MyResultsWorldImpl : IMyResultsWorld
+{
+    public static float StringError(float a)
+    {
+        return a;
+    }
+}
diff --git a/test/WitBindgenTest/testapps/LibraryWithExceptions/result.wit b/test/WitBindgenTest/testapps/LibraryWithExceptions/result.wit
@@ -0,0 +1,5 @@
+package test:results;
+
+world my-results {
+  export string-error: func(a: f32) -> result<f32, string>;
+}
diff --git a/test/WitBindgenTest/testapps/LibraryWithWitResultType/LibraryWithWitResultType.csproj b/test/WitBindgenTest/testapps/LibraryWithWitResultType/LibraryWithWitResultType.csproj
@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <!-- Only needed when referencing the dependencies as projects. For package references, these are imported automatically. -->
+    <Import Project="..\..\..\..\src\WitBindgen\ImportInDev.proj" />
+
+    <PropertyGroup>
+        <TargetFramework>net9.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <WitBindgenAddtionalArgs>--with-wit-results</WitBindgenAddtionalArgs>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\..\..\..\src\WitBindgen\WitBindgen.csproj" />
+      <PackageReference Include="runtime.$(NETCoreSdkPortableRuntimeIdentifier).Microsoft.DotNet.ILCompiler.LLVM"/>
+    </ItemGroup>
+
+    <ItemGroup>
+      <Wit Update="result.wit" />
+    </ItemGroup>
+
+</Project>
diff --git a/test/WitBindgenTest/testapps/LibraryWithWitResultType/Result.cs b/test/WitBindgenTest/testapps/LibraryWithWitResultType/Result.cs
@@ -0,0 +1,13 @@
+// I don't think this namespace should be so different to the one in MyFuncsWorldImpl,
+// but currently that's what the codegen requires
+using MyWitResultsWorld;
+
+
+
+public class MyWitResultsWorldImpl : IMyWitResultsWorld
+{
+    public static Result<float, string> StringError(float a)
+    {
+        return Result<float, string>.Ok(a);
+    }
+}
diff --git a/test/WitBindgenTest/testapps/LibraryWithWitResultType/result.wit b/test/WitBindgenTest/testapps/LibraryWithWitResultType/result.wit
@@ -0,0 +1,5 @@
+package test:results;
+
+world my-wit-results {
+  export string-error: func(a: f32) -> result<f32, string>;
+}