FSharp.Grpc.Tools 0.1.9

FSharp.Grpc

F# code generation from .proto files. Generates F# records, enums, and discriminated unions with binary and JSON serialization. Generates gRPC server and client stubs.

Documentation

• — setup, type mapping, JSON, examples
• — setup, handler signatures, all streaming patterns, testing
• — setup, client creation, all streaming patterns

Overview

syntax = "proto3";
package example;

message Person {
 string name = 1;
 int32 age = 2;
}

open Example

let alice = { Person.empty with Name = "Alice"; Age = 30 }

let bytes = Person.encode alice
let decoded = Person.decode bytes

let json = Person.encodeJson alice
// {"name":"Alice","age":30}

Getting started

dotnet new console -lang F# -n MyApp
cd MyApp
dotnet add package FSharp.Grpc.Tools.Codegen

Add a proto file and register it in your .fsproj:

<ItemGroup>
 <Protobuf Include="protos/person.proto"/>
</ItemGroup>

Build and use the generated types:

dotnet build

open Example

let request = { Person.empty with Name = "World"; Age = 30 }
let bytes = Person.encode request
let json = Person.encodeJson request

Features

gRPC services

Set GrpcServices metadata to generate server and client stubs:

<Protobuf Include="protos/greeter.proto" GrpcServices="Both"/>

Server

open Greeter
open Microsoft.AspNetCore.Builder
open Microsoft.Extensions.DependencyInjection

let handlers: GreeterHandlers =
 { SayHello =
 fun req ctx ->
 task { return { HelloReply.empty with Message = $"Hello {req.Name}!" } } }

let builder = WebApplication.CreateBuilder()
builder.Services.AddGrpc() |> ignore
builder.Services.AddSingleton(GreeterService(handlers)) |> ignore
let app = builder.Build()
app.MapGrpcService<GreeterService>() |> ignore
app.Run()

Client

open Greeter

let run () = task {
 let client = GreeterClient.create "https://localhost:5001"
 let! reply = client.SayHello { HelloRequest.empty with Name = "World" }
 printfn "%s" reply.Message
}

Supported patterns: unary, server streaming, client streaming, bidirectional streaming.

Wire compatibility

Generated code produces the same wire format as C#, Go, Java, Python, and other protobuf implementations. Tested with 50 cross-language serialization tests and 10 cross-language gRPC tests (F# server + C# client, C# server + F# client).

Benchmarks

Apple M3 Max, .NET 10.0:

Binary

Person (2 fields):

ScalarTypes (15 fields):

UserProfile (enum, nested message, repeated, maps, oneof):

UserProfile, high cardinality (1,000 repeated ints + 100 nested messages — exercises the sub-message decode path):

JSON

Person (2 fields):

ScalarTypes (15 fields):

UserProfile (enum, nested message, repeated, maps, oneof):

Requirements

• .NET 8.0 SDK or later
• protoc is resolved automatically from the Grpc.Tools NuGet package

Limitations

• Proto3 only. Proto2 syntax is not supported.
• The deprecated group field type is rejected.

License

MIT. See .

Developed with Claude Code.