Add netcoreapp3.0 ref to System.IO.Pipelines package

Directory.Build.targets

@@ -156,6 +156,9 @@
     <Message Text="Generated reference assembly source code: $(_RefSourceFileOutputPath)" />
   </Target>
 
+  <!-- Import Packaging targets -->
+  <Import Project="$(RepositoryEngineeringDir)Packaging.targets" />
+
   <Import Project="$(RepositoryEngineeringDir)DisableSourceControlManagement.targets" Condition="'$(EnableSourceLink)' == 'false'" />
 
   <!-- Define this now until we can clean-up targets that depend on it in the packaging targets -->

eng/Packaging.targets

@@ -0,0 +1,25 @@
+<Project>
+  <!--     There are some packages where we require only one ref for a specific framework to be present. In order to avoid problems with this package when targetting 
+           dektop with RAR we will make sure there are no exclude=compile references in the package.
+    For more info, please check issues:
+     - https://github.com/dotnet/corefx/issues/32457  -> Why reference assets were removed from the package
+     - https://github.com/aspnet/AspNetCore/issues/11206  -> Why ASP.NET required a ref to be added back for netcoreapp
+     - https://github.com/dotnet/corefx/issues/38729  -> Issue tracking to work of readding a ref to netcoreapp -->
+  <Target Name="RemoveExcludeCompileFromPackageDependencies" Condition="'$(RemoveExcludeCompileFromPackageDependencies)' == 'true'" DependsOnTargets="GetPackageDependencies" BeforeTargets="ValidateExcludeCompileDesktop">
+    <ItemGroup>
+      <Dependency>
+        <Exclude></Exclude>
+      </Dependency>
+    </ItemGroup>    
+  </Target>
+
+  <Target Name="ValidateExcludeCompileDesktop" AfterTargets="GetPackageDependencies" Inputs="%(Dependency.Identity);%(Dependency.TargetFramework)" Outputs="unused">
+    <PropertyGroup>
+      <_excludeCompile Condition="@(Dependency->WithMetadataValue('Exclude', 'Compile')->Count()) == @(Dependency->Count())">true</_excludeCompile>
+    </PropertyGroup>
+    <Error Text="Cannot have Exclude=Compile dependencies when targeting a desktop TFM. @(Dependency). You can exclude the reference asset in the package by setting the ExcludeReferenceAssets property to true in your project." 
+           Condition="$([System.String]::Copy('%(Dependency.TargetFramework)').StartsWith('net4')) AND 
+                      '$(_excludeCompile)' == 'true' AND
+                      '%(Dependency.Identity)' != '_._'" />
+  </Target>
+</Project>

src/Directory.Build.targets

@@ -54,15 +54,4 @@
   <Target Name="GetDocumentationFile"
           Returns="$(DocumentationFile)"/>
 
-  <!-- This target will be moved into buildtools. Checked in here for now to add validationand in order not to block buildtools ingestion. -->
-  <Target Name="ValidateExcludeCompileDesktop" AfterTargets="GetPackageDependencies" Inputs="%(Dependency.Identity);%(Dependency.TargetFramework)" Outputs="unused">
-    <PropertyGroup>
-      <_excludeCompile Condition="@(Dependency->WithMetadataValue('Exclude', 'Compile')->Count()) == @(Dependency->Count())">true</_excludeCompile>
-    </PropertyGroup>
-    <Error Text="Cannot have Exclude=Compile dependencies when targeting a desktop TFM. @(Dependency). You can exclude the reference asset in the package by setting the ExcludeReferenceAssets property to true in your project." 
-           Condition="$([System.String]::Copy('%(Dependency.TargetFramework)').StartsWith('net4')) AND 
-                      '$(_excludeCompile)' == 'true' AND
-                      '%(Dependency.Identity)' != '_._'" />
-  </Target>
-
 </Project>

src/System.IO.Pipelines/pkg/System.IO.Pipelines.pkgproj

@@ -1,16 +1,16 @@
 <Project DefaultTargets="Build">
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), Directory.Build.props))\Directory.Build.props" />
+  <PropertyGroup>
+    <!-- This package is part of the ASP.NET Targeting pack so we require a netcoreapp ref in the package.
+    In order to avoid problems with RAR when targeting desktop, we remove all exclude=compile from package dependencies. -->
+    <RemoveExcludeCompileFromPackageDependencies>true</RemoveExcludeCompileFromPackageDependencies>
+  </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\ref\System.IO.Pipelines.csproj">
       <SupportedFramework>net461;netcoreapp2.0;uap10.0.16299;$(AllXamarinFrameworks)</SupportedFramework>
     </ProjectReference>
     <ProjectReference Include="..\src\System.IO.Pipelines.csproj" />
     <HarvestIncludePaths Include="lib/netstandard1.3" />
   </ItemGroup>
-  <PropertyGroup>
-    <!-- Excluding the reference assets on the package so that RAR will see the run-time conflicts at build time in order to
-    generate the right binding redirects when targeting Desktop. https://github.com/dotnet/corefx/issues/32457 -->
-    <ExcludeReferenceAssets>true</ExcludeReferenceAssets>
-  </PropertyGroup>
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), Directory.Build.targets))\Directory.Build.targets" />
 </Project>

src/System.IO.Pipelines/ref/System.IO.Pipelines.csproj

@@ -2,6 +2,9 @@
   <PropertyGroup>
     <ProjectGuid>{9C524CA0-92FF-437B-B568-BCE8A794A69A}</ProjectGuid>
     <Configurations>netstandard-Debug;netstandard-Release</Configurations>
+    <!-- We only plan to use this ref in netcoreapp. For all other netstandard compatible frameworks we should use the lib
+    asset instead. -->
+    <PackageTargetFramework Condition="'$(TargetGroup)' == 'netstandard'">netcoreapp2.0</PackageTargetFramework>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.IO.Pipelines.cs" />