Description

The Microsoft.NET.Test.Sdk NuGet package version 17.4.0-preview-20220726-02 and later now always inserts buildTransitive/netcoreapp3.1/Microsoft.NET.Test.Sdk.Program.cs into to the build of referencing projects, which can result in CS0017 build errors.

Steps to reproduce

Download and extract vstest-cs0017.zip.

The project consists of two projects, App and TestHelper. App.csproj has @(ProjectReference) to TestHelper.csproj , and TestHelper.csproj has a @(PackageReference) to two different versions of Microsoft.NET.Test.Sdk, depending on whether $(UseStable) is True.

Build the project:

cd vstest-cs0017
dotnet build App/App.csproj

Expected behavior

It builds!

Actual behavior

It doesn't build:

Program.cs(2,24): error CS0017: Program has more than one entry point defined. Compile with /main to specify the type that contains the entry point.

However, if you use an older Microsoft.NET.Test.Sdk package version, it does build!

dotnet build App/App.csproj -p:UseStable=True
# no errors!

Discussion

The problem is caused solely by the Microsoft.NET.Test.Sdk package version. App.csproj builds when using 16.11.0, and fails with 17.5.0-preview-20221003-04.

The breakage appears to have been introduced between 17.4.0-preview-20220707-01 (works) and 17.4.0-preview-20220726-02 (fails). The primary difference appears to be that 17.4.0-preview-20220726-02 moved build/netcoreapp2.1/Microsoft.NET.Test.Sdk.Program.cs to buildTransitive/netcoreapp2.1/Microsoft.NET.Test.Sdk.Program.cs, causing it to be included into indirectly referencing projects such as App.csproj.

Workaround

Use an older version of Microsoft.NET.Test.Sdk.

Or set the $(StartupObject) MSBuild property.

Or do as #636 suggests and set $(GenerateProgramFile)=false.

Environment

This is with .NET 7.0.100-rc.1.22431.12.

AB#1662932