Multi-target project with 2 versions of the same dependency depending on target framework

[Mrcubix]

I was wondering how i would go about achieving multi-targeting for my project, as I'm making Two separate extensions for Two different versions of an application.

My solution goes as follows:

root
├───.modules
│   ├───OpenTabletDriver.External
│   ├───OpenTabletDriver.External-0.6.x
│   ├───OTD.EnhancedOutputMode
│   └───OTD.EnhancedOutputMode-0.6.x
├───Touch-Gestures
├───Touch-Gestures-0.6.x
├───Touch-Gestures.Installer
├───Touch-Gestures.Lib
├───Touch-Gestures.Tests
├───Touch-Gestures.UX
└───Touch-Gestures.UX.Desktop

Touch-Gestures targets net5.0, while Touch-Gestures-0.6.x targets net6.0.

Both of those libraries have Touch-Gestures.Lib as a dependency. Ideally, this Library should target multiple version of .NET & dependencies in .modules.

Now here is the issue i am encountering:

If i target multiple frameworks in Touch-Gestures.Lib (using <TargetFrameworks>net5.0;net6.0</TargetFrameworks>) then,
Dependencies with net6.0 as target will overwrite the ones with .net5.0 target.
This result in builds of Touch-Gestures failing, because it's targeting net5.0, but the libraries isn't making use of the net5.0 dependencies as it should.

Touch-Gestures csproj file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net5.0</TargetFramework>
    <NoWarn>$(NoWarn); NETSDK1138</NoWarn>
    <RootNamespace>TouchGestures</RootNamespace>
  </PropertyGroup>

  <!-- Only Embed debug symbols for the Release configuration -->
  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
    <DebugType>embedded</DebugType>
  </PropertyGroup>

  <ItemGroup>
    <ProjectReference Include="../Touch-Gestures.Lib/Touch-Gestures.Lib.csproj" />
    <ProjectReference Include="../.modules/OpenTabletDriver.External/.modules/OpenTabletDriver/OpenTabletDriver.Desktop/OpenTabletDriver.Desktop.csproj" />
    <ProjectReference Include="../.modules/OTD.EnhancedOutputMode/OTD.EnhancedOutputMode.Lib/OTD.EnhancedOutputMode.Lib.csproj" />
  </ItemGroup>

</Project>

Touch-Gestures-0.6.x csproj file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <NoWarn>$(NoWarn); NETSDK1138</NoWarn>
    <RootNamespace>TouchGestures</RootNamespace>
    <AssemblyName>Touch-Gestures</AssemblyName>
  </PropertyGroup>

  <!-- Only Embed debug symbols for the Release configuration -->
  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
    <DebugType>embedded</DebugType>
  </PropertyGroup>

  <ItemGroup>
    <ProjectReference Include="../Touch-Gestures.Lib/Touch-Gestures.Lib.csproj" />
    <ProjectReference Include="../.modules/OpenTabletDriver.External-0.6.x/.modules/OpenTabletDriver/OpenTabletDriver.Desktop/OpenTabletDriver.Desktop.csproj" />
    <ProjectReference Include="../.modules/OTD.EnhancedOutputMode-0.6.x/OTD.EnhancedOutputMode.Lib/OTD.EnhancedOutputMode.Lib.csproj" />
  </ItemGroup>

</Project>

Touch-Gestures.Lib csproj file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>net5.0;net6.0</TargetFrameworks>
    <LangVersion>preview</LangVersion>
    <RootNamespace>TouchGestures.Lib</RootNamespace>
    <NoWarn>$(NoWarn); NETSDK1138; VSTHRD200</NoWarn>
    <Nullable>enable</Nullable>
    <!-- TODO: Change obj path to obj/0.5.x to avoid conflicts with 0.6.x (.NET bug) -->
  </PropertyGroup>

  <!-- Only Embed debug symbols for the Release configuration -->
  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
    <DebugType>embedded</DebugType>
  </PropertyGroup>

  <!-- Only for OTD 0.5.x (Running on .NET 5) -->
  <ItemGroup Condition="'$(TargetFramework)' == 'net5.0'">
    <ProjectReference Include="../.modules/OpenTabletDriver.External/.modules/OpenTabletDriver/OpenTabletDriver.Desktop/OpenTabletDriver.Desktop.csproj" PrivateAssets="all" />
    <ProjectReference Include="../.modules/OpenTabletDriver.External/OpenTabletDriver.External.Common/OpenTabletDriver.External.Common.csproj" />
  </ItemGroup>

  <!-- Only for OTD 0.6.x (Running on .NET 6) -->
  <ItemGroup Condition="'$(TargetFramework)' == 'net6.0'">
    <ProjectReference Include="../.modules/OpenTabletDriver.External-0.6.x/.modules/OpenTabletDriver/OpenTabletDriver.Desktop/OpenTabletDriver.Desktop.csproj" PrivateAssets="all" />
    <ProjectReference Include="../.modules/OpenTabletDriver.External-0.6.x/OpenTabletDriver.External.Common/OpenTabletDriver.External.Common.csproj" />
  </ItemGroup>
</Project>

If you build Touch-Gestures (which targets net5.0) as is, dotnet will say that the project isn't compatible with the library, because it and its dependencies are targeting net6.0, which shouldn't be the case since the condition is there to prevent that.

Now what i've also tried is using different csproj files, targeting different versions of .NET & dependencies.

That approach seems to work on individual builds, however, i am unable to build the solution as a whole, as nuget will only restore Touch-Gestures.Lib.csproj, skipping Touch-Gestures.Lib-0.6.x.csproj, the following error occur.

error NETSDK1005: Assets file 'Touch-Gestures\Touch-Gestures.Lib\obj\project.assets.json' doesn't have a target for 'net5.0'. Ensure that restore has run and that you have included 'net5.0' in the TargetFrameworks for your project. [Touch-Gestures\Touch-Gestures.Lib\Touch-Gestures.Lib.csproj::TargetFramework=net5.0]

After that error occurred, i have tried to change the obj folder for each csproj, but that also ended up not working, as .NET's compiler ended up detecting source generated files for each of these folders as duplicates, also it still generate an obj folder. containing the same content as without having that Directory.Build.Props file.

<Project InitialTargets="PrintAllVariables">

  <!-- Change obj folder for .NET 5 and .NET 6 -->
  <PropertyGroup Condition="'$(TargetFramework)' == 'net5.0'">
    <MSBuildProjectExtensionsPath>obj-0.5.x</MSBuildProjectExtensionsPath>
    <BaseIntermediateOutputPath>obj-0.5.x</BaseIntermediateOutputPath>
    <IntermediateOutputPath>obj-0.5.x/$(Configuration)</IntermediateOutputPath>

    <!-- exclude obj-0.6.x folder to prevent conflicts -->
    <DefaultItemExcludes>$(DefaultItemExcludes);obj-0.6.x\**</DefaultItemExcludes>
  </PropertyGroup>

  <PropertyGroup Condition="'$(TargetFramework)' == 'net6.0'">
    <MSBuildProjectExtensionsPath>obj-0.6.x</MSBuildProjectExtensionsPath>
    <BaseIntermediateOutputPath>obj-0.6.x</BaseIntermediateOutputPath>
    <IntermediateOutputPath>obj-0.6.x/$(Configuration)</IntermediateOutputPath>

    <!-- exclude obj-0.5.x folder to prevent conflicts -->
    <DefaultItemExcludes>$(DefaultItemExcludes);obj-0.5.x\**</DefaultItemExcludes>
  </PropertyGroup>

</Project>

Touch-Gestures\Touch-Gestures\Touch-Gestures.csproj : error NU1201: Project OpenTabletDriver.Desk is not compatible with net5.0 (.NETCoreApp,Version=v5.0). Project OpenTabletDriver.Plugin supports: net6.0 (.NETCoreApp,Version=v6.0) [Touch-Gestures\Touch-Gestures.sln]

Of course, using <Compile Remove="obj-0.6.x" /> in net5.0 or <Compile Remove="obj-0.5.x" /> in net6.0 does not solve the issue.
The same applies to DefaultItemExcludes.

Any way i can achieve what i want?

This feels similar to dotnet/sdk#17013.