Generate F# from Morphir

Compile a Morphir model JSON file into F# as part of an ordinary build. This article uses the supplied car rental example and calls its generated inventory and billing functions.

Prerequisites

• A checkout of finos/morphir-dotnet.
• The .NET SDK pinned in global.json, currently 10.0.403.
• Access to NuGet for package restore.

Run the following commands from the repository root. The checked-in model is sufficient; a separate Morphir frontend is not required.

Choose the plugin version

Morphir.Myriad is published to NuGet.org with each morphir-dotnet release, from 0.4.0-alpha.2. This article uses 0.4.0-alpha.2; use the version of the release you want.

Morphir.Myriad includes its backend, build task and the matched Myriad 0.85.0 host. Myriad.Core 0.85.0 and Fantomas.Core 7.0.5 are the matching plugin dependencies. The bundled host uses an aligned FSharp.Core and major-version roll forward to load the .NET 10 plugin, including on the first cold restore.

Configure the model input

The example’s examples/car-rental/CarRental.fsproj references the plugin and declares the JSON input once:

<ItemGroup>
  <PackageReference Include="Morphir.Myriad" Version="0.4.0-alpha.2" PrivateAssets="all" />
  <MorphirModel Include="models/car-rental-v3.json" />
  <Compile Include="Program.fs" />
</ItemGroup>

This snippet uses ordinary NuGet version syntax for a standalone project. In this repository the example uses VersionOverride with MorphirMyriadVersion to work with central package management. Do not add JSON to Compile or enumerate generated modules by hand.

Restore and run

dotnet restore examples/car-rental/CarRental.fsproj \
  --configfile examples/car-rental/NuGet.config -p:MorphirMyriadVersion=0.4.0-alpha.2
dotnet run --project examples/car-rental/CarRental.fsproj --no-restore -p:MorphirMyriadVersion=0.4.0-alpha.2

The supplied NuGet configuration restores every package from NuGet.org, and keeps the repository’s own source mapping out of the example. The application prints:

dailyRate=5000
inventory=Available
reservation=Reserved
pickup=Rented
return=Available
invoice=15000
rejections=7

The first generated value is Car.Rental.Inventory.dailyRate. The driver also calls Inventory.lookup "CAR-1" [ Inventory.car ], then executes the reservation, pickup, return and billing functions. Three billable days at 5000 cents per day produce a 15000-cent invoice. The final line confirms that seven invalid operations returned the expected business errors.

Inspect the F# output

Look beneath examples/car-rental/obj/<configuration>/net10.0/morphir/. The model has seven generated files: Domain.fs, Inventory.fs, Reservation.fs, Pickup.fs, Return.fs, Billing.fs and Workflow.fs. The accompanying manifest.json lists them in dependency order. Myriad inserts them before Program.fs in compilation.

Edit the model JSON or its optional F# authoring script, then rebuild. Generated files are build artifacts and are regenerated; do not edit them directly.

Next steps

Follow the car rental tutorial for the full model, state transitions, error cases and a rate-change exercise. Consult the plugin reference for configuration, compatibility and build failures.