dotnet · ViktorHofer · Sep 28, 2020 · Oct 4, 2020 · Oct 6, 2020 · Oct 8, 2020
diff --git a/docs/workflow/building/libraries/README.md b/docs/workflow/building/libraries/README.md
@@ -6,7 +6,8 @@ Here is one example of a daily workflow for a developer working mainly on the li
 
 ```bat
 :: From root:
-git clean -xdf
+:: Clean artifacts directory without removing the bootstrapped .dotnet folder. 
+build -clean
 git pull upstream master & git push origin master
 :: Build Debug libraries on top of Release runtime:
 build.cmd clr+libs -rc Release
@@ -23,14 +24,15 @@ cd tests
 
 :: Then inner loop build / test
 :: (If using Visual Studio, you might run tests inside it instead)
-pushd ..\src & dotnet build & popd & dotnet build /t:test
+dotnet build /t:test
 ```
 
 The instructions for Linux and macOS are essentially the same:
 
 ```bash
 # From root:
-git clean -xdf
+# Clean artifacts directory without removing the bootstrapped .dotnet folder.
+build -clean
 git pull upstream master & git push origin master
 # Build Debug libraries on top of Release runtime:
 ./build.sh clr+libs -rc Release
@@ -43,7 +45,7 @@ cd src/libraries/System.Text.RegularExpressions
 cd tests
 
 # Then inner loop build / test:
-pushd ../src & dotnet build & popd & dotnet build /t:test
+dotnet build /t:test
 ```
 
 The steps above may be all you need to know to make a change. Want more details about what this means? Read on.

diff --git a/eng/references.targets b/eng/references.targets
@@ -21,13 +21,36 @@
                       PrivateAssets="all" />
   </ItemGroup>
 
+  <!-- Annotate the CoreLib P2P with required attributes. -->
+  <ItemGroup>
+    <ProjectReference Update="$(CoreLibProject)">
+      <Private>false</Private>
+      <SetConfiguration Condition="'$(RuntimeFlavor)' == 'CoreCLR' and
+                                    '$(Configuration)' != '$(CoreCLRConfiguration)'">Configuration=$(CoreCLRConfiguration)</SetConfiguration>
+      <SetConfiguration Condition="'$(RuntimeFlavor)' == 'Mono' and
+                                    '$(Configuration)' != '$(MonoConfiguration)'">Configuration=$(MonoConfiguration)</SetConfiguration>
+      <!-- Don't flow TargetFramework and Platform to use same inputs and outputs as the CoreLib's build as part of the runtime. -->
+      <UndefineProperties>$(UndefineProperties);TargetFramework;Platform</UndefineProperties>
+    </ProjectReference>
+  </ItemGroup>
+
   <!-- Project references shouldn't be copied to the output for non test apps. -->
   <ItemDefinitionGroup Condition="'$(IsTestProject)' != 'true' and '$(IsTestSupportProject)' != 'true'">
     <ProjectReference>
       <Private>false</Private>
     </ProjectReference>
   </ItemDefinitionGroup>
 
+  <!-- Disable TargetArchitectureMismatch warning when we reference CoreLib which is platform specific. -->
+  <Target Name="SetAssemblyWarnOnErrorOnTargetArchitectureForCoreLib"
+          BeforeTargets="ResolveAssemblyReferences"
+          Condition="'@(ProjectReference)' != '' and
+                     @(ProjectReference->AnyHaveMetadataValue('Identity', '$(CoreLibProject)'))">
+    <PropertyGroup>
+      <ResolveAssemblyWarnOrErrorOnTargetArchitectureMismatch>None</ResolveAssemblyWarnOrErrorOnTargetArchitectureMismatch>
+    </PropertyGroup>
+  </Target>
+
   <!-- Filter out transitive P2Ps which should be excluded. -->
   <Target Name="FilterTransitiveProjectReferences"
           AfterTargets="IncludeTransitiveProjectReferences"
@@ -42,17 +65,23 @@
     </ItemGroup>
   </Target>
 
-  <!-- Make shared framework assemblies not app-local (non private). -->
-  <Target Name="UpdateProjectReferencesWithPrivateAttribute"
-          AfterTargets="AssignProjectConfiguration"
-          BeforeTargets="PrepareProjectReferences"
+  <!--
+    Make shared framework assemblies not app-local (non private), don't reference them and flow
+    the TargetFramework-TargetOS touple to avoid tfm selection.
+  -->
+  <Target Name="UpdateSharedFrameworkProjectReferences"
+          BeforeTargets="ResolveP2PReferences;AssignProjectConfiguration"
           Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' and
                      ('$(IsTestProject)' == 'true' or '$(IsTestSupportProject)' == 'true') and
-                     '@(ProjectReferenceWithConfiguration)' != ''">
+                     '@(ProjectReference)' != ''">
     <ItemGroup>
-      <ProjectReferenceWithConfiguration PrivateAssets="all"
-                                         Private="false"
-                                         Condition="$(NetCoreAppLibrary.Contains('%(Filename);'))" />
+      <ProjectReference Condition="$(NetCoreAppLibrary.Contains('%(Filename);'))">
+        <PrivateAssets>all</PrivateAssets>
+        <Private>false</Private>
+        <ReferenceOutputAssembly Condition="!$(NetCoreAppLibraryNoReference.Contains('%(Filename);')) and
+                                            '%(ProjectReference.SkipUseReferenceAssembly)' != 'true'">false</ReferenceOutputAssembly>
+        <ReferringTargetFramework Condition="'$(TargetFrameworkSuffix)' == ''">$(TargetFramework)-$(TargetOS)</ReferringTargetFramework>
-        <ReferringTargetFramework Condition="'$(TargetFrameworkSuffix)' == ''">$(TargetFramework)-$(TargetOS)</ReferringTargetFramework>
+        <ReferringTargetFramework>$(BuildTargetFramework)-$(TargetOS)</ReferringTargetFramework>
-        <ReferringTargetFramework Condition="'$(TargetFrameworkSuffix)' == ''">$(TargetFramework)-$(TargetOS)</ReferringTargetFramework>
+        <ReferringTargetFramework>$(BuildTargetFramework)-$(TargetOS)</ReferringTargetFramework>
+      </ProjectReference>
     </ItemGroup>
   </Target>
 

diff --git a/src/libraries/Common/tests/TestUtilities/TestUtilities.csproj b/src/libraries/Common/tests/TestUtilities/TestUtilities.csproj
@@ -71,8 +71,8 @@
   <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
     <!-- Upgrade the NetStandard.Library transitive xunit dependency to avoid 1.x NS dependencies. -->
     <PackageReference Include="NETStandard.Library" Version="$(NetStandardLibrary20Version)" />
-    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Win32.Registry\ref\Microsoft.Win32.Registry.csproj" PrivateAssets="all" />
-    <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Principal.Windows\ref\System.Security.Principal.Windows.csproj" PrivateAssets="all" />
+    <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Win32.Registry\src\Microsoft.Win32.Registry.csproj" />
+    <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Principal.Windows\src\System.Security.Principal.Windows.csproj" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'net461'">
     <PackageReference Include="System.Memory" Version="$(SystemMemoryVersion)" />

diff --git a/src/libraries/Directory.Build.targets b/src/libraries/Directory.Build.targets
@@ -1,5 +1,4 @@
-<Project InitialTargets="UpdateProjectReferencesWithAttributes">
-
+<Project>
   <Import Project="..\..\Directory.Build.targets" />
 
   <PropertyGroup>
@@ -167,24 +166,6 @@
   <!-- Define this target to override the workaround in arcade as we don't need it for our pkgprojs -->
   <Target Name="InitializeStandardNuspecProperties" />
 
-  <Target Name="UpdateProjectReferencesWithAttributes" Condition="'@(ProjectReference)' != ''">
-    <ItemGroup>
-      <ProjectReference Condition="'%(Filename)' == 'System.Private.CoreLib'">
-        <!-- Don't flow TargetFramework and Platform to use same inputs and outputs as the CoreLib's build as part of the runtime. -->
-        <UndefineProperties>$(UndefineProperties);TargetFramework;Platform</UndefineProperties>
-        <SetConfiguration Condition="'$(RuntimeFlavor)' == 'CoreCLR' and
-                                     '$(Configuration)' != '$(CoreCLRConfiguration)'">Configuration=$(CoreCLRConfiguration)</SetConfiguration>
-        <SetConfiguration Condition="'$(RuntimeFlavor)' == 'Mono' and
-                                     '$(Configuration)' != '$(MonoConfiguration)'">Configuration=$(MonoConfiguration)</SetConfiguration>
-        <Private>false</Private>
-      </ProjectReference>
-    </ItemGroup>
-    <!-- Disable TargetArchitectureMismatch warning when we reference CoreLib which is platform specific. -->
-    <PropertyGroup Condition="@(ProjectReference->AnyHaveMetadataValue('Identity', '$(CoreLibProject)'))">
-      <ResolveAssemblyWarnOrErrorOnTargetArchitectureMismatch>None</ResolveAssemblyWarnOrErrorOnTargetArchitectureMismatch>
-    </PropertyGroup>
-  </Target>
-
   <!-- Used for packaging -->
   <Target Name="IsNotNetCoreAppProject" Returns="@(IsNotNetCoreAppProjectResult)">
     <ItemGroup>
@@ -284,5 +265,4 @@
       </ItemGroup>
     </When>
   </Choose>
-
 </Project>
diff --git a/src/libraries/Microsoft.CSharp/tests/Microsoft.CSharp.Tests.csproj b/src/libraries/Microsoft.CSharp/tests/Microsoft.CSharp.Tests.csproj
@@ -35,9 +35,12 @@
     <Compile Include="UserDefinedShortCircuitOperators.cs" />
     <Compile Include="VarArgsTests.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+  <ItemGroup Condition="$(TargetFramework.StartsWith('$(NetCoreAppCurrent)'))">
     <Compile Include="AccessTests.netcoreapp.cs" />
   </ItemGroup>
+  <ItemGroup Condition="$(TargetFramework.StartsWith('$(NetCoreAppCurrent)'))">
+    <ProjectReference Include="..\src\Microsoft.CSharp.csproj" />
+  </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'net48'">
     <Reference Include="Microsoft.CSharp" />
   </ItemGroup>

diff --git a/src/libraries/Microsoft.VisualBasic.Core/tests/Microsoft.VisualBasic.Core.Tests.csproj b/src/libraries/Microsoft.VisualBasic.Core/tests/Microsoft.VisualBasic.Core.Tests.csproj
@@ -50,6 +50,9 @@
     <Compile Include="UtilsTests.cs" />
     <Compile Include="VBMathTests.cs" />
   </ItemGroup>
+  <ItemGroup Condition="$(TargetFramework.StartsWith('$(NetCoreAppCurrent)'))">
+    <ProjectReference Include="..\src\Microsoft.VisualBasic.Core.vbproj" />
+  </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'net461'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Text.Encoding.CodePages\src\System.Text.Encoding.CodePages.csproj" />
     <Reference Include="Microsoft.VisualBasic" />

diff --git a/src/libraries/Microsoft.Win32.Primitives/tests/Microsoft.Win32.Primitives.Tests.csproj b/src/libraries/Microsoft.Win32.Primitives/tests/Microsoft.Win32.Primitives.Tests.csproj
@@ -5,4 +5,7 @@
   <ItemGroup>
     <Compile Include="Win32ExceptionTests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\Microsoft.Win32.Primitives.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/NetCoreAppLibrary.props b/src/libraries/NetCoreAppLibrary.props
@@ -76,6 +76,7 @@
       System.Net.WebSockets.Client;
       System.Numerics.Vectors;
       System.ObjectModel;
+      System.Private.CoreLib;
       System.Private.DataContractSerialization;
       System.Private.Runtime.InteropServices.JavaScript;
       System.Private.Uri;
@@ -149,6 +150,12 @@
       Microsoft.Win32.Registry;
       System.IO.FileSystem.AccessControl;
       System.IO.Pipes.AccessControl;
+      System.Private.CoreLib;
+      System.Private.DataContractSerialization;
+      System.Private.Runtime.InteropServices.JavaScript;
+      System.Private.Uri;
+      System.Private.Xml;
+      System.Private.Xml.Linq;
       System.Security.AccessControl;
       System.Security.Cryptography.Cng;
       System.Security.Cryptography.OpenSsl;

diff --git a/src/libraries/System.AppContext/tests/System.AppContext.Tests.csproj b/src/libraries/System.AppContext/tests/System.AppContext.Tests.csproj
@@ -7,4 +7,7 @@
     <Compile Include="AppContext.Switch.cs" />
     <Compile Include="AppContext.Switch.Validation.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.AppContext.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Buffers/tests/System.Buffers.Tests.csproj b/src/libraries/System.Buffers/tests/System.Buffers.Tests.csproj
@@ -11,4 +11,7 @@
     <Compile Include="ArrayPool\UnitTests.cs" />
     <Compile Include="$(CommonTestPath)System\Diagnostics\Tracing\TestEventListener.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Buffers.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj b/src/libraries/System.Collections.Concurrent/tests/System.Collections.Concurrent.Tests.csproj
@@ -70,4 +70,7 @@
     <Compile Include="$(CommonTestPath)System\Collections\IEnumerable.Generic.Serialization.Tests.cs"
              Link="Common\System\Collections\IEnumerable.Generic.Serialization.Tests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Collections.Concurrent.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Collections.NonGeneric/tests/System.Collections.NonGeneric.Tests.csproj b/src/libraries/System.Collections.NonGeneric/tests/System.Collections.NonGeneric.Tests.csproj
@@ -41,4 +41,7 @@
     <Compile Include="$(CommonTestPath)System\Collections\IEnumerable.NonGeneric.Serialization.Tests.cs"
              Link="Common\System\Collections\IEnumerable.NonGeneric.Serialization.Tests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Collections.NonGeneric.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/...ibraries/System.Collections.Specialized/tests/System.Collections.Specialized.Tests.csproj b/...ibraries/System.Collections.Specialized/tests/System.Collections.Specialized.Tests.csproj
@@ -77,4 +77,7 @@
              Link="Common\System\Collections\IEnumerable.NonGeneric.Serialization.Tests.cs" />
     <Compile Include="NameObjectCollectionBase\NameObjectCollectionBase.ConstructorTests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Collections.Specialized.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Collections/tests/System.Collections.Tests.csproj b/src/libraries/System.Collections/tests/System.Collections.Tests.csproj
@@ -126,4 +126,7 @@
     <Compile Include="$(CommonTestPath)System\Collections\IDictionary.NonGeneric.Tests.netcoreapp.cs"
              Link="Common\System\Collections\IDictionary.NonGeneric.Tests.netcoreapp.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Collections.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/...es/System.ComponentModel.Annotations/tests/System.ComponentModel.Annotations.Tests.csproj b/...es/System.ComponentModel.Annotations/tests/System.ComponentModel.Annotations.Tests.csproj
@@ -42,6 +42,9 @@
     <Compile Include="System\ComponentModel\DataAnnotations\ValidationResultTests.cs" />
     <Compile Include="System\ComponentModel\DataAnnotations\ValidatorTests.cs" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+    <ProjectReference Include="..\src\System.ComponentModel.Annotations.csproj" />
+  </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'net48'">
     <Reference Include="System.ComponentModel.DataAnnotations" />
   </ItemGroup>

diff --git a/...m.ComponentModel.EventBasedAsync/tests/System.ComponentModel.EventBasedAsync.Tests.csproj b/...m.ComponentModel.EventBasedAsync/tests/System.ComponentModel.EventBasedAsync.Tests.csproj
@@ -14,4 +14,7 @@
     <Compile Include="BackgroundWorkerTests.cs" />
     <Compile Include="TestException.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.ComponentModel.EventBasedAsync.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/...ries/System.ComponentModel.Primitives/tests/System.ComponentModel.Primitives.Tests.csproj b/...ries/System.ComponentModel.Primitives/tests/System.ComponentModel.Primitives.Tests.csproj
@@ -27,4 +27,7 @@
     <Compile Include="System\ComponentModel\ReadOnlyAttributeTests.cs" />
     <Compile Include="System\ComponentModel\RefreshPropertiesAttributeTests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.ComponentModel.Primitives.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/...ystem.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj b/...ystem.ComponentModel.TypeConverter/tests/System.ComponentModel.TypeConverter.Tests.csproj
@@ -152,6 +152,7 @@
     <Compile Include="XTypeDescriptionProviderTests.cs" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\src\System.ComponentModel.TypeConverter.csproj" />
     <PackageReference Include="System.ComponentModel.TypeConverter.TestData" Version="$(SystemComponentModelTypeConverterTestDataVersion)" />
     <PackageReference Include="Moq" Version="$(MoqVersion)" />
   </ItemGroup>

diff --git a/src/libraries/System.ComponentModel/tests/System.ComponentModel.Tests.csproj b/src/libraries/System.ComponentModel/tests/System.ComponentModel.Tests.csproj
@@ -6,4 +6,7 @@
     <Compile Include="CancelEventArgsTests.cs" />
     <Compile Include="ComponentModelBasicTests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.ComponentModel.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Console/tests/ManualTests/System.Console.Manual.Tests.csproj b/src/libraries/System.Console/tests/ManualTests/System.Console.Manual.Tests.csproj
@@ -6,4 +6,7 @@
   <ItemGroup>
     <Compile Include="ManualTests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\System.Console.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Console/tests/System.Console.Tests.csproj b/src/libraries/System.Console/tests/System.Console.Tests.csproj
@@ -45,4 +45,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Fcntl.cs"
              Link="Common\Interop\Unix\System.Native\Interop.Fcntl.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Console.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Data.Common/src/System.Data.Common.csproj b/src/libraries/System.Data.Common/src/System.Data.Common.csproj
@@ -306,7 +306,7 @@
     <ProjectReference Include="..\..\System.ComponentModel.TypeConverter\src\System.ComponentModel.TypeConverter.csproj" />
     <ProjectReference Include="..\..\System.Runtime\src\System.Runtime.csproj" />
     <ProjectReference Include="..\..\System.Runtime.Extensions\src\System.Runtime.Extensions.csproj" />
-    <ProjectReference Include="..\..\System.Private.Uri\src\System.Private.Uri.csproj" />
+    <ProjectReference Include="..\..\System.Private.Uri\src\System.Private.Uri.csproj" PrivateAssets="all" />
     <Reference Include="System.Collections.Concurrent" />
     <Reference Include="System.ComponentModel" />
     <Reference Include="System.ComponentModel.Primitives" />

diff --git a/src/libraries/System.Data.Common/tests/System.Data.Common.Tests.csproj b/src/libraries/System.Data.Common/tests/System.Data.Common.Tests.csproj
@@ -119,8 +119,9 @@
     <Compile Include="$(CommonTestPath)System\Runtime\Serialization\Formatters\BinaryFormatterHelpers.cs"
              Link="Common\System\Runtime\Serialization\Formatters\BinaryFormatterHelpers.cs" />
   </ItemGroup>
-  <!-- S.D.SqlClient isn't live built anymore. -->
   <ItemGroup>
+    <!-- S.D.SqlClient isn't live built anymore. -->
     <PackageReference Include="System.Data.SqlClient" Version="$(SystemDataSqlClientVersion)" />
+    <ProjectReference Include="..\src\System.Data.Common.csproj" />
   </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Data.DataSetExtensions/tests/System.Data.DataSetExtensions.Tests.csproj b/src/libraries/System.Data.DataSetExtensions/tests/System.Data.DataSetExtensions.Tests.csproj
@@ -14,8 +14,10 @@
     <Compile Include="System\Data\TypedTableBaseExtensionsTests.cs" />
   </ItemGroup>
   <ItemGroup>
-    <Content Include="Mono\testdataset1.xml">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </Content>
+    <Content Include="Mono\testdataset1.xml"
+             CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Data.DataSetExtensions.csproj" />
   </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Diagnostics.Contracts/tests/System.Diagnostics.Contracts.Tests.csproj b/src/libraries/System.Diagnostics.Contracts/tests/System.Diagnostics.Contracts.Tests.csproj
@@ -14,4 +14,7 @@
     <Compile Include="$(CommonTestPath)System\ShouldNotBeInvokedException.cs"
              Link="Common\System\ShouldNotBeInvokedException.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\src\System.Diagnostics.Contracts.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Diagnostics.Debug/tests/System.Diagnostics.Debug.Tests.csproj b/src/libraries/System.Diagnostics.Debug/tests/System.Diagnostics.Debug.Tests.csproj
@@ -6,14 +6,6 @@
     <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix</TargetFrameworks>
     <TestRuntime>true</TestRuntime>
   </PropertyGroup>
-  <ItemGroup>
-    <DefaultReferenceExclusion Include="System.Diagnostics.Debug" />
-    <DefaultReferenceExclusion Include="System.Runtime.Extensions" />
-    <ProjectReference Include="$(CoreLibProject)" />
-    <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime\src\System.Runtime.csproj;
-                               $(LibrariesProjectRoot)System.Threading\src\System.Threading.csproj"
-                      SkipUseReferenceAssembly="true" />
-  </ItemGroup>
   <ItemGroup>
     <Compile Include="DebugTests.cs" />
     <Compile Include="DebugTestsNoListeners.cs" />
@@ -26,4 +18,14 @@
     <Compile Include="EmptyAttributeTests.cs" />
     <Compile Include="XunitAssemblyAttributes.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="$(CoreLibProject)" />
+    <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime\src\System.Runtime.csproj;
+                               $(LibrariesProjectRoot)System.Threading\src\System.Threading.csproj"
+                      SkipUseReferenceAssembly="true" />
+    <ProjectReference Include="..\src\System.Diagnostics.Debug.csproj" />
+    <!-- Do not reference since we build part of the source code for tests. -->
+    <DefaultReferenceExclusion Include="System.Diagnostics.Debug" />
+    <DefaultReferenceExclusion Include="System.Runtime.Extensions" />
+  </ItemGroup>
 </Project>