Bending .NET - Corrected Common Flat Build Output

[Stefan75]

Hello,

@nietras
I read your blog post:
Blog Post

In the blog post you stated that you have to import in every cs project file a prop file:

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

  <PropertyGroup>
    <TargetFrameworks>net5.0;net6.0</TargetFrameworks>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <Import Project="$(MSBuildThisFileDirectory)..\OutputBuildProject.props" />
</Project>

Here the content of the OutputBuildProjects.props file:

<Project>
  <PropertyGroup>
    <OutDir>$(BaseOutDir)_$(TargetFramework)\</OutDir>
    <TargetDir>$(OutDir)</TargetDir>
    <PublishDir>$(BasePublishDir)$(ProjectBuildDirectoryName)</PublishDir>
    <PublishDir Condition="$(TargetFramework) != ''">$(PublishDir)_$(TargetFramework)</PublishDir>
    <PublishDir Condition="$(RuntimeIdentifier) != ''">$(PublishDir)_$(RuntimeIdentifier)</PublishDir>
  </PropertyGroup>
</Project>

I guess the reason is that some of your properties depends on the settings of the cs-project file self.
(e.g. depends on TargetFramework)

Maybe I found a solution, because I have a similar problem.

During my work I found the MS-Build Property BeforeTargetFrameworkInferenceTargets.
It is possible to set the property to a msbuild-file which is then evaluated in a very early phase of the target-file evaulation, much earlier than the Directory.Build.targets file.

Some parts of the Direcotry.Build.props file content

<!--    Hook addional targets file -->
<PropertyGroup>		 
 <BeforeTargetFrameworkInferenceTargets>$(MSBuildThisFileDirectory)BeforeTargetFrameworkInference.targets</BeforeTargetFrameworkInferenceTargets>
</PropertyGroup>

Some parts of the BeforeTargetFrameworkInference.targets file content:

<PropertyGroup Condition=" $([System.Text.RegularExpressions.Regex]::IsMatch($(TargetFramework), '^netstandard')) ">
    <DotNetStandard>true</DotNetStandard>
  </PropertyGroup>
  <PropertyGroup Condition=" $([System.Text.RegularExpressions.Regex]::IsMatch($(TargetFramework), '^net[5-9]')) ">
    <DotNet5AndLater>true</DotNet5AndLater>
  </PropertyGroup>
  <PropertyGroup Condition=" $([System.Text.RegularExpressions.Regex]::IsMatch($(TargetFramework), '^net[4]')) ">
    <DotNet4>true</DotNet4>
  </PropertyGroup>

  <Target Name="Test" AfterTargets="Build">
    <Message Text="BUILD-TEST: .NET Standard detected" Condition="'$(DotNetStandard)' == 'true'" Importance="high" />
    <Message Text="BUILD-TEST: .NET 4 detected" Condition="'$(DotNet4)' == 'true'" Importance="high" />
    <Message Text="BUILD-TEST: .NET 5 or later detected" Condition="'$(DotNet5AndLater)' == 'true'" Importance="high" />
  </Target>

Here I used the TargetFrmework value for some debug outputs.

Some remarks:

• I found the hook with help of the MSBuild Structured Logviewer
• I didn't find any earlier hook.
• My wish would be to have a hook which is executed as early as possible.
  We want to use such a hook to define global defaults which depend on cs-projct-file content.
  (e.g. OutptuType, ...)
• I hope that this hook is executed early enough for my tasks, will see.

With best regards,
stefan

PS: I hope my post helps.

[nietras]

Hey @Stefan75, thank you very much for your comment.

I actually saw the issue where someone (you?) commented on using BeforeTargetFrameworkInferenceTargets in a normal target and I also tried it. However, I did not try it exactly the way you describe it though with:

<PropertyGroup>		 
<BeforeTargetFrameworkInferenceTargets>$(MSBuildThisFileDirectory)BeforeTargetFrameworkInference.targets</BeforeTargetFrameworkInferenceTargets>
</PropertyGroup>

I just tried this out, and I believe it works! 🎉

I simply forward to and import the OutputBuildProject.props in BeforeTargetFrameworkInference.targets:

<Project>
  <Import Project="$(MSBuildThisFileDirectory)\OutputBuildProject.props" />
</Project>

I have attached a zip with this approach.

CommonFlatBuild.zip

Comments are welcome. F12 appears to work. Build looks same.

Thanks!
Niels

PS: BeforeTargetFrameworkInferenceTargets is mentioned in dotnet/sdk#14931
PPS: dotnet/runtime appears to use this trick too in https://github.com/dotnet/runtime/blob/75c0b990ce249d6c37adfa4037ef3ba5b280085c/src/libraries/Directory.Build.props#L14, so it should be validated by that https://github.com/dotnet/runtime/blob/main/eng/BeforeTargetFrameworkInference.targets
PPPS: The target is indeed simply imported in https://github.com/dotnet/sdk/blob/main/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.TargetFrameworkInference.targets and hence the indirection is not really needed as such, the important thing is the comment:

Note that this file is only included when $(TargetFramework) is set and so we do not need to check that here.