WACS.ComponentModel.Async.SourceGen 0.4.25

WACS.ComponentModel.Async.SourceGen

Roslyn incremental source generator that backs the Component Model async dispatcher in WACS.ComponentModel. Three independent generators, each replacing what would otherwise be a runtime-reflection scan — satisfying the WACS AOT-safety rule (no [RequiresDynamicCode], no late-bound discovery).

Packaged as analyzers/dotnet/cs — no runtime DLL is shipped or referenced; the generator runs at consumer build time only.

What it produces

1. [AsyncComponentHarness] — typed async harness for a .component.wasm

The headline surface. Mark a partial class with [AsyncComponentHarness] and per-export [AsyncExport] / [SyncExport] partial methods; the generator emits the ctor + each method body, wired through ComponentInstance.InstantiateAot

• InvokeCoreAsyncLift so the consumer's code stays on the AOT-safe primitive surface.

using Wacs.ComponentModel.Async;

[AsyncComponentHarness]
public partial class MyComponent
{
    [AsyncExport("wasi:cli/run@0.3.0-draft/run")]
    public partial Task<Result<Unit, Unit>> RunAsync(CancellationToken ct);

    [SyncExport("local:demo/math#add")]
    public partial int Add(int a, int b);
}

Lift naming follows wit-component: [async-lift]<qualified-export> for async-lifted exports, plain export name for sync. The AsyncExport / SyncExport strings are opaque to the generator — they pass through to the runtime lifter lookup.

For the canonical-ABI shapes the generator currently supports (records, variants, lists, options, results, strings) and what's still punted, see the memory note project_async_sourcegen_surface — or just try it; the diagnostics on unsupported shapes name the specific WIT type.

2. [CanonAsync(...)] — CanonOpRegistry.BuildKnownNames

Runs against Wacs.ComponentModel itself. Scans AsyncDispatcher for methods decorated [CanonAsync("...")] (e.g. [async-lower], subtask.drop, stream.new) and emits the partial BuildKnownNames() implementation supplying the static set of known canon-async op names. The hand-written registry declares partial HashSet<string> BuildKnownNames(); and this generator fills it in.

Replaces the prior reflection-on-first-access path so the registry has zero runtime reflection.

3. [ComponentLifter(...)] — [ModuleInitializer] registration

Runs in every consumer assembly that ships a [ComponentLifter("wit-id")]-marked static method. Emits a [ModuleInitializer]-decorated registration method that calls ComponentLifterRegistry.Register once per match at assembly load.

Lets per-host packages (WACS.WASI.Preview3, future WACS.WASI.Preview3.Http, etc.) self-register their lifters without a central, manually-maintained registration list.

How it relates to the other WACS packages

Wiring it into a project

Reference as an analyzer (mirrors how Bindgen.SourceGen is wired):

<ItemGroup>
  <PackageReference Include="WACS.ComponentModel.Async.SourceGen"
                    Version="*"
                    PrivateAssets="all" />
  <PackageReference Include="WACS.ComponentModel" Version="*" />
</ItemGroup>

The first generator (AsyncComponentHarness) needs Wacs.ComponentModel.Async.AsyncComponentHarnessAttribute to be resolvable in the compilation — pulling WACS.ComponentModel satisfies all three triggers' attribute references.

AOT story

Three generators replace what would have been three reflection sites:

1. Per-component harness construction: was ComponentInstance.Invoke (reflective bridge) → now generated partial method bodies on InstantiateAot / InvokeCoreAsyncLift.
2. Canon-op registry: was reflective scan of AsyncDispatcher on first access → now generated partial method.
3. Lifter registry: was central manually-maintained list → now [ModuleInitializer] per consumer assembly.

Each is verified by the WACS AOT acceptance gate (AotAcceptanceTests) — publishing the bench package with PublishAot=true must produce no new IL trim warnings.

License

Apache-2.0