Paket restore silently fails when TargetFramework(s) are specified in Directory.Build.props and not csproj

Description

When TargetFramework(s) are defined in Directory.Build.props Paket restore silently fails, it should be able to get it from msbuild at runtime.

Repro steps

Have Directory.Build.props in solution root folder e.g.:

<Project>
 <Import Project=".\Versions.props"/>
  <PropertyGroup>
      <FullFrameworkVersion>net462</FullFrameworkVersion>
   </PropertyGroup>
</Project>

and then use the property to define TargetFramework in underlying project files, e.g.:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
   <TargetFramework>$(FullFrameworkVersion)</TargetFramework>
    <AssemblyName>SomeAssembly</AssemblyName>
...
  </PropertyGroup>
  <Import Project="..\..\.paket\Paket.Restore.targets" />
</Project>

Expected behavior

Paket restore shouldn’t silently fail. Ideally it should be able to get Framework information from msbuild from runtime.

Actual behavior

Paket restore is not able to get TargetFramework(s) information from project file and silently fails.

Known workarounds

Don’t define TargetFramework in Directory.Build.props . #3013

[matthid]

@alfonsogarciacaro https://github.com/fsprojects/Paket/blob/7346d01d237ebe489a61bb699deb07ee8be8357b/src/Paket.Core/PaketConfigFiles/DependencyCache.fs#L34-L92

This basically is the implementation to get an order, implemented on package and on dll level. Basically all you need to have is a function getting dependencies. Here we use Mono.Cecil on dll-level and our own infos for package level

[vbfox]

Copy pasting from slack, after discussing why generating dozen of .paket.resolved could be annoying if there was no detection (and that all supported framework were generated):

A single XML file could be generated and read like this :

<paket>
    <dep fw=";netstandard1.6;netstandard2.0;">Microsoft.NETCore.Platforms,2.0.1,Transitive,Main,false</dep>
    <dep fw=";netstandard1.6;netstandard2.0;">Microsoft.NETCore.Targets,2.0,Transitive,Main,false</dep>
</paket>

    <Target Name="Xml">
        <XmlPeek
            XmlInputPath="Test.xml" Query="/paket/dep[contains(@fw,'netstandard2.0')]/text()">
            <Output
                TaskParameter="Result"
                ItemName="ItemsFromFile"/>
        </XmlPeek>
        <Message Text="Hello @(ItemsFromFile)" Importance="high"/>
    </Target>

(Instead of the current ReadLinesFromFile)