使 MSBuild 目标依赖于来自不同项目的目标

Question

I have a setup where I have an API (ASP.NET) project and a test project to test the API. I use NSwag to auto-generate an API client in the test project through the following steps:

1. After the API project is built, use NSwag to generate an OpenAPI definition from the produced DLL
2. Before building the API test project, use the OpenAPI definition produced in (1) to generate/update a C# API client

These steps are done through MSBuild targets:

<!-- API Project -->
<Project Sdk="Microsoft.NET.Sdk.Web">
  <Target Name="GenerateApiDefinition" BeforeTargets="AfterBuild">
    <!-- Use NSwag to generate an openapi.json output file based on the built DLL -->
  </Target>
</Project>

<!-- API test project -->
<Project Sdk="Microsoft.NET.Sdk">
  <ProjectReference Include="..\ApiProject\ApiProject.csproj" />

  <Target Name="GenerateApiClient" BeforeTargets="BeforeBuild">
    <!-- Consumes the openapi.json file generated by project A to generate/update a C# API client class -->
  </Target>
</Project>

This works when building with Visual Studio or MSBuild, because the projects are built sequentially in order. It will fully build the API project first, then it will build the test project.

But it doesn't work when I try to build the clean solution using dotnet build . I will receive an error for the test project explaining that the openapi.json file does not exist. This error will only happen the first time I build -- if I use dotnet build again, the build will work because the file was generated in the previous build.

It seems that dotnet build somehow builds the projects in parallel, at least to some degree. I am thinking the test project cannot compile before the API project is compiled since it has a project reference, but maybe the pre-build steps are performed in parallel?

I have tried to change the BeforeTargets attribute to Compile and other values, but I am stuck with either getting the error for the missing API definition file, or an error explaining the auto-generated ApiClient class was not generated, indicating that I am hooking the target in either too early (before the GenerateApiDefinition target has completed) or too late (after the build process needs to have the class defined).

What I would really like to do is to make the GenerateApiClient target depend on the GenerateApiDefinition target in the other project. I don't know if it is possible to make target dependencies between projects? Is there another way I can go about this?

Answer 1

There isn't a way to have the GenerateApiClient target in the 'API test' project depend on the GenerateApiDefinition target in the 'API' Project.

MSBuild will try to build projects in parallel. If the test project is supplied to the dotnet build command, the project reference in the test project will be used to find and build the API project. Clearly the compile step in the test project needs the API project to be up to date.

I tested the following change to the 'API Test' project and it seems to solve the issue:

  <Target Name="GenerateApiClient" BeforeTargets="CoreCompile">

It would seem that MSBuild considers that targets before the build (ie BeforeTargets="BeforeBuild" ) can be run in parallel. Changing the GenerateApiClient target to depend on CoreCompile instead seems to cause MSBuild to treat it as a target that must wait for the API build to complete (which the CoreCompile target itself must do).

I created a mockup of the project setup that you described and I replicated your issue. Then I changed the dependency to CoreCompile . After the change the GenerateApiClient target never ran too early.