Custom build task is not called when building on solution level

[shhsu]

Steps to reproduce

Hi:

I have created a nuget package to redistribute IIS Web Manager (currently named Microsoft.IIS.WebManager.Middleware). It's a static website. There's a build task in the nuget package that would copy the website content to a project's wwwroot directory if this nuget package is imported. The example usage was (https://github.com/shhsu/IIS.WebManager/blob/shhsu/proj/src/Microsoft.IIS.WebManager.SelfHost/Microsoft.IIS.WebManager.SelfHost.csproj)

Project file

<Project Sdk="Microsoft.NET.Sdk.Web">
  <Import Project="$(MSBuildProjectDirectory)\..\build\global.props" />
  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <OutputPath>$(MSBuildProjectDirectory)\..\..\artifacts\WebManagerApp</OutputPath>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App" version="2.1.0" />
    <PackageReference Include="Microsoft.IIS.WebManager.Middleware" Version="$(IISWebManagerVersion)" PrivateAssets="All" />
  </ItemGroup>
  <Target Name="PreBuild" BeforeTargets="PreBuildEvent">
    <Exec Command="dotnet restore" />
  </Target>
</Project>

Directory contents:
See https://github.com/shhsu/IIS.WebManager/tree/shhsu/proj

Command line
Edit the solution file Microsoft.IIS.WebManager.sln and re-enable building Microsoft.IIS.WebManager.SelfHost project (I disabled it because it didn't work as expected)
Call:

msbuild Microsoft.IIS.WebManager.sln

Expected behavior

The output directory WebManagerApp should contains a wwwroot directory.

Actual behavior

The wwwroot directory does not exist.

NOTE:
I was able to workaround the issue by disabling build of Microsoft.IIS.WebManager.SelfHost from solution.
And I would call
msbuild Microsoft.IIS.WebManager.sln
and build Microsoft.IIS.WebManager.Middleware first, then I would build Microsoft.IIS.WebManager.SelfHost by itself

cd Microsoft.IIS.WebManager.SelfHost
dotnet restore
msbuild

This seem to generate the result as expected, WebManagerApp has the correct content in wwwroot directory

Environment data

msbuild /version output: 15.7.177.53362

OS info:
Version 10.0.17134 Build 17134

If applicable, version of the tool that invokes MSBuild (Visual Studio, dotnet CLI, etc):

[rainersigwald]

Do I understand correctly that you're both building the NuGet package and referencing it inside the same build? That definitely won't work, because project imports can't be updated after it is loaded. That means:

1. The project is loaded (because the solution references it)
   a. At this time, there's no NuGet package to reference, so it's not imported.
2. The PreBuild target happens, running dotnet restore
   a. The next time the project is loaded, it would see the now-restored package
3. The build finishes, using the project from 1, because that's the build that was started.
   a. This instance of the project doesn't have your custom target.

For your scenario, I think you'd like something like dotnet/sdk#1151, but that doesn't currently exist.

[shhsu]

I see. What you are describing is exactly my issue. You can close this issue as a duplicate then.

[rainersigwald]

Duplicate of dotnet/sdk#1151

[rainersigwald]

Oh, and your workaround of building in phases sounds pretty reasonable to me, given the current state of things.