F# codegen: behavioural run-step under TypeLoadMode.Static (GH-2969)

[jeremydmiller]

Part of the F# code-generation audit (#2969). Every slice so far is a compile-gate (proves the generated F# compiles). This adds the missing run-verified harness: it boots a real Wolverine host in TypeLoadMode.Static against a pre-generated F# handler adapter and asserts the handler actually executes.

How it works

• Wolverine.Behavioural.FSharpApp (F#) is a self-contained application assembly carrying BOTH an F# handler (BehaviouralPingHandler, which records to an in-process sink) AND its pre-generated F# adapter (Generated.fs).
• Wolverine.Behavioural.FSharpTests:
  • generated_fsharp_handler_runs_under_static_load — boots a host with TypeLoadMode.Static + ApplicationAssembly = the F# app, sends a BehaviouralPing(42), and asserts the sink recorded 42. Wolverine loads the pre-generated F# MessageHandler by name (BehaviouralPingHandler1244766258) from the app's exported types and executes it — no Roslyn at runtime.
  • generated_fsharp_regenerates_and_compiles — regenerates Generated.fs from the shared BehaviouralCodegen.Configure and dotnet builds the app, so the committed F# adapter can't silently drift from the codegen output.

Key mechanics discovered

• Set opts.ApplicationAssembly (not just CodeGeneration.ApplicationAssembly) — it cascades to CodeGeneration.ApplicationAssembly and survives bootstrap (the re-establish step is gated on _applicationAssembly == null), so static load scans the F# app, not the test assembly.
• The generated F# handler type is public (exported), so assembly.ExportedTypes.FirstOrDefault(x => x.Name == TypeName) finds it, and QuickBuild instantiates it via its primary constructor — F# generated handlers slot straight into Wolverine's static loader.
• A shared config between generation and runtime keeps the generated type-name hash in sync (a drift throws ExpectedTypeMissingException at startup — a loud signal).

Wire-up & verification

• App + test added to wolverine_fsharp.slnx; fsharp.yml runs the behavioural run-step as its own sequential step.
• Both facts green; full wolverine_fsharp.slnx builds clean. No production-code changes (pure test/harness), so wolverine.slnx is unaffected.

This upgrades the audit's strongest guarantee from "the generated F# compiles" to "the generated F# compiles and runs," and is the template for run-verifying any future slice.

🤖 Generated with Claude Code