F# codegen: Marten document slice — runnable sample + compile-gate (GH-2969)

[jeremydmiller]

Part of the F# code-generation audit (#2969), following the EF Core slice (#2983). This is the second store-specific slice: Marten document persistence, with its own runnable F# sample + compile-gate.

Marten document frame F# emit

Both in Wolverine.Marten/Codegen — and no JasperFx release needed this time (both are Wolverine-side):

• OpenMartenSessionFrame → use session = factory.OpenSession(context). C# await using var becomes F# use — inside the task { } CE that disposes the IAsyncDisposable session at block end. Covers the no-context (native Marten) and tenant-id branches too.
• CreateDocumentSessionFrame → the create-session + eager-idempotency branches (use session = …, do! context.AssertEagerIdempotencyAsync(ct)).

SaveChangesAsync and the outbox flush are MethodCall/already-F# frames.

Generated F# (from the gate):

task {
    // Building the Marten session
    use documentSession = _outboxedSessionFactory.OpenSession(context)
    let createProductCommand = context.Envelope.Message :?> WolverineMartenFSharpSample.CreateProductCommand
    let outgoing1 = WolverineMartenFSharpSample.CreateProductHandler.Handle(createProductCommand, documentSession)
    do! context.EnqueueCascadingAsync(outgoing1)
    do! documentSession.SaveChangesAsync(cancellation)
    do! context.FlushOutgoingMessagesAsync()
}

Runnable sample — src/Samples/WolverineMartenFSharpSample

F# Product/CreateProductCommand/ProductCreated + a [<Transactional>] CreateProductHandler storing through an injected IDocumentSession. Marten is both the document store and (via IntegrateWithWolverine) the durable message store backing the transactional outbox. Postgres-backed — not infra-free (the static F# story is the compile-gate's job). Runs via dynamic codegen (Wolverine.RuntimeCompilation + opts.UseRuntimeCompilation(), #2876). Verified end-to-end: prints Created a Product through the F# Wolverine + Marten handler.

Compile-gate — src/Testing/Wolverine.Marten.FSharp{Tests,Fixture}

Renders the sample's real CreateProductCommand chain to F# via the no-host HandlerGraph → AssembleTypes → GenerateFSharpCode path, then dotnet builds the checked-in fixture (FS0193/lock retry). Mirrors the Core/Http/EfCore gates.

Wire-up

• Sample + gate added to wolverine_fsharp.slnx.
• fsharp.yml runs the Marten document gate as its own sequential step.

Verification

• Marten document compile-gate green.
• dotnet build wolverine.slnx -c Release clean (per CLAUDE.md the slim build isn't sufficient).
• Sample runs end-to-end on Postgres.

Next slice: the Marten event-sourced aggregate (MartenOps.StartStream, [Aggregate] loading) — the heaviest frame set.

🤖 Generated with Claude Code