IndependentReserve.Grpc.Tools 4.0.194

IndependentReserve.Grpc.Tools

Purpose

This package contains MSBuild tasks and targets for automatic generation of gRPC/Protobuf code from plain C# interface(s).

How it works

When this package is referenced by a project it adds itself into compilation pipeline in the following way:
For every depended project which is marked by GenerateGrpc attribute it loads all eligible C# interfaces and for every such source interface it generates the following code:

• a set of *.proto files defining gRPC service and messages plus the hierarchy of all DTO classes referenced by the source interface;
• a set of C# partial classes which provide implicit conversion operators for Protobuf ↔ DTO conversion for every generated *.proto file;
• gRPC service implementation which depends on source interface and internally calls this interface for corresponding interface method implementation;
• gRPC client class which implements the source interface by calling gRPC server via gRPC.

How to use it

To generate all required gRPC/Protobuf code in a project you need to point the package to a separate project which contains interface (or interfaces) which you want to generate gRPC/Protobuf types for. To do that simply add GenerateGrpc="true" attribute to ProjectReference element of the relevant source project, e.g.:

<ItemGroup>
  <ProjectReference Include="..\Service.Interface.csproj" GenerateGrpc="true" />
</ItemGroup>

By default the tool searches for all public interfaces which names match Service$ regular expression (e.g. ISomeService) and generates all required gRPC-related code for every found interface.
To use a different pattern for interface search specify a custom regular expression (.NET flavor) via GrpcServicePattern attribute, e.g.:

<ItemGroup>
  <ProjectReference Include="..\Service.Interface.csproj" >
    <GenerateGrpc>true</GenerateGrpc>
    <GrpcServicePattern>I[^.]*ServiceInterface$</GrpcServicePattern>
  </ProjectReference>
</ItemGroup>  

Note: the source interfaces must be in a separate dependent project because the tool uses reflection to load and process source interfaces during the build.

All generated files are placed in obj/[Configuration]/[TargetFramework]/Grpc root folder and are automatically included into project's build.
All *.proto files are placed in Protos subfolder:

• [service-name].proto file: gRPC service definition file which defines all methods mirroring source interface methods;
• [service-name]/Messages/*.proto files: these files contain all *Request and *Response messages referenced from [service-name].proto file;
• [class-name].proto files: a hierarchy of messages which are referenced (directly or indirectly) by messages from [service-name]Messages.proto.

All *.cs files are placed in Partials subfolder:

• [service-name]GrpcService.cs: gRPC service class:
  This class depends on the source interface and it is expected that the implementation of this interface passed to gRPC service class constructor (e.g. via dependency injection) contains the internal implementation of the service logic;
• [service-name]GrpcClient.cs: gRPC client implementation:
  This class implements source interface by calling the service via gRPC (using internal gRPC client class in turn generated by Grpc.Tools). For each method from source interface both synchronous and asynchronous methods are generated.
• [class-name].cs files: a set of partial C# classes which add implicit conversion operators (Protobuf ↔ DTO) to generated by Grpc.Tools C# classes.
  There is one to one correspondence between this set and [class-name].proto files set.

From the above set of files normally only C# code is relevant to the user of this package. The Protobuf code can be considered internal. In practice developer only needs to know about two classes:

• gRPC service: to host the service in ASP.NET;
• gRPC client: to call the service.

Both classes either depend or implement the source interface while all boilerplate conversion to/from Protobuf messages is handled by AutoMapper framework.

.NET to Protobuf conversion rules

• Every public method of source interface is converted to gRPC service method;
• Every .NET type which is referenced by any convertible source interface method directly or transitively is converted to Protobuf message using the following approach:
  • Any well-known built-in type, i.e. a type which has direct corresponding Protobuf type (e.g. Boolean, Int32, String, etc.) or one of built-in .NET-specific types from IndependentReserve.Grpc package (e.g.: Decimal, Guid, DateTime etc.) is directly convertible;
  • A collection (i.e. a type which implements IEnumerable<> interface, including IDictionary<,>) or a single-dimensional array (including jagged arrays) with elements of convertible type are convertible;
  • Enums are convertible (but see note below);
  • For any other .NET type a custom Protobuf message is generated using all public fields and properties of convertible types;
  • Any .NET entity which is not convertible (i.e. which is ignored or is not currently supported) is omitted during Protobuf code generation (with detailed MSBuild warning issued in build log). Such ignored entity will be absent in Protobuf code and will most likely always have default value in source type.

Ignored .NET entities

The following .NET entities are ignored (i.e. they are not convertible):

• Open generic source interfaces;
• Interfaces and abstract classes (except for classes and interfaces which implement IEnumerable<> interface);
• Any type which is not built-in and does not have any convertible public fields or properties.

Currently not supported .NET entities

The following .NET entities are not currently supported (i.e. they are currently not convertible) but they might be supported in future versions:

• Nested .NET types;
• Multidimensional arrays;
• Enums with underlying type smaller than Int32;
• ref and out source interface method parameters;
• Source interface properties;
• Source interface open generic methods without default implementation;
• Source interface events;

Nullable annotations

The tool takes into account nullable annotations when they are available. Generally not-nullable arguments and type members produce more efficient Protobuf code. This is especially noticiable in collections, e.g. serialisation of a property of type string[] (i.e. an array of non-nullable string) is several times faster than serialisation of a similar property but of type string?[] (i.e. an array which can contain null elements).

gRPC Streaming

Generated code use gRPC streaming to handle return type of a method or a single argument of a method of type IEnumerable<> or IAsyncEnumerable<>.

Example of generated C# code

If we pass the following source interface to the tool:

public interface ITestService
{
    int Plus(int a, int b);
}

it will generate the following gRPC service class:

public partial class TestServiceGrpcService : TestServiceBase
{
    private readonly ILogger<TestServiceGrpcService> _logger;
    private readonly ITestService _testService;

    public TestServiceGrpcService(
        ILogger<TestServiceGrpcService> logger,
        ITestService testService)
    {
        _logger = logger;
        _testService = testService;
    }

    public override async Task<PlusResponse> Plus(PlusRequest request, ServerCallContext context)
    {
        var args = MapperTo<ValueTuple<System.Int32, System.Int32>>.MapFrom(new { Item1 = request.A, Item2 = request.B });
        var result = _testService.Plus(args.Item1, args.Item2);
        return MapperTo<PlusResponse>.MapFrom(new { Result = result });
    }
}

along with the following gRPC client class:

public partial class TestServiceGrpcClient : GrpcClient, ITestService
{
    private readonly Lazy<TestServiceClient> _client;

    public TestServiceGrpcClient(IGrpcServiceConfiguration config, bool useGrpcWeb = true)
        : base(config, useGrpcWeb)
    {
        var invoker = Channel.CreateCallInvoker();
        SetupCallInvoker(ref invoker);
        _client = new(() => new(invoker));
    }

    partial void SetupCallInvoker(ref CallInvoker invoker);

    private TestServiceClient Client => _client.Value;

    public System.Int32 Plus(System.Int32 a, System.Int32 b)
    {
        var response = Client.Plus(MapperTo<PlusRequest>.MapFrom(new { A = a, B = b }));
        return MapperTo<Wrapper<System.Int32>>.MapFrom(response).Result;
    }

    public async Task<System.Int32> PlusAsync(System.Int32 a, System.Int32 b)
    {
        var response = await Client.PlusAsync(MapperTo<PlusRequest>.MapFrom(new { A = a, B = b }));
        return MapperTo<Wrapper<System.Int32>>.MapFrom(response).Result;
    }
}

DTO ↔ Protobuf conversion code test generation

This tool can also generate unit tests for DTO → gRPC → byte[] → gRPC → DTO (round-trip) conversion/serialization path which check that after conversion/serialization the source DTO content is matched by the resulting DTO content.
To add test generation step to a project add GenerateGrpcTests="true" attribute to the ProjectReference to the source interface project, e.g.:

<ItemGroup>
  <ProjectReference Include="..\Service.Interface.csproj" GenerateGrpcTests="true" />
</ItemGroup>

The tool then generates unit tests for every DTO referenced by the source interface. It uses xUnit since this test framework allows test input being provided by an external class via ClassData attribute. Every test is run against generated test data (random DTO content). By default it generates 1000 random DTO instances in every test. This limit can be controlled by setting Arbitrary.TestCount property, e.g.:

  public partial class TestServiceConversionTests
  {
      static TestServiceConversionTests()
      {
          Arbitrary.TestCount = 10000;
      }
  }

Note: GenerateGrpcTests="true" does not generate source Protobuf code (only tests) since normally unit tests are placed in a separate project which references a project which contains generated (via GenerateGrpc="true") Protobuf code. If you require both code and the tests to be generated in the same project add both GenerateGrpc and GenerateGrpcTests attributes to relevant ProjectReference.