Get WPF inner-builds to import NuGet packages' imports

Workaround for https://github.com/dotnet/wpf/issues/810

Directory.Build.props

@@ -40,4 +40,31 @@
     <!-- We always want MSBuild properties generated that point at the restored location of each package. -->
     <PackageReference GeneratePathProperty="true" />
   </ItemDefinitionGroup>
+
+  <PropertyGroup Condition="'$(IsWpfTempProject)' == ''">
+    <IsWpfTempProject>false</IsWpfTempProject>
+    <IsWpfTempProject Condition="$(MSBuildProjectName.EndsWith('_wpftmp'))">true</IsWpfTempProject>
+  </PropertyGroup>
+
+  <!--
+    Inspired by https://github.com/dotnet/arcade/blob/cbfa29d4e859622ada3d226f90f103f659665d31/src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.props#L14-L31
+    WPF temp-projects do not import .props and .targets files from NuGet packages.
+    (see https://github.com/dotnet/sourcelink/issues/91).
+
+    Property _TargetAssemblyProjectName is set by GenerateTemporaryTargetAssembly task.
+    Disable Source Link and Xliff in WPF temp projects to avoid generating non-deterministic file names to obj dir.
+    The project name is non-deterministic and is included in the Source Link json file name and xlf directory names.
+    It's also not necessary to generate these assets.
+  -->
+  <PropertyGroup Condition="'$(IsWpfTempProject)' == 'true'">
+    <_WpfTempProjectNuGetFilePathNoExt>$(RepoRootPath)obj\$(_TargetAssemblyProjectName)\$(_TargetAssemblyProjectName)$(MSBuildProjectExtension).nuget.g</_WpfTempProjectNuGetFilePathNoExt>
+
+    <EnableSourceLink>false</EnableSourceLink>
+    <EmbedUntrackedSources>false</EmbedUntrackedSources>
+    <DeterministicSourcePaths>false</DeterministicSourcePaths>
+    <EnableXlfLocalization>false</EnableXlfLocalization>
+  </PropertyGroup>
+
+  <!-- Workaround https://github.com/dotnet/wpf/issues/810 -->
+  <Import Project="$(_WpfTempProjectNuGetFilePathNoExt).props" Condition="'$(_WpfTempProjectNuGetFilePathNoExt)' != '' and Exists('$(_WpfTempProjectNuGetFilePathNoExt).props')"/>
 </Project>

Directory.Build.targets

@@ -1,2 +1,8 @@
 <Project>
+  <PropertyGroup>
+    <!-- Workaround https://github.com/dotnet/wpf/issues/1718 -->
+    <EmbedUntrackedSources Condition=" '$(UseWPF)' == 'true' ">false</EmbedUntrackedSources>
+  </PropertyGroup>
+
+  <Import Project="$(_WpfTempProjectNuGetFilePathNoExt).targets" Condition="'$(_WpfTempProjectNuGetFilePathNoExt)' != '' and Exists('$(_WpfTempProjectNuGetFilePathNoExt).targets')"/>
 </Project>

src/Directory.Build.targets

@@ -1,8 +1,3 @@
 <Project>
-  <PropertyGroup>
-    <!-- Workaround https://github.com/dotnet/wpf/issues/1718 -->
-    <EmbedUntrackedSources Condition=" '$(UseWPF)' == 'true' ">false</EmbedUntrackedSources>
-  </PropertyGroup>
-
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)../, Directory.Build.targets))\Directory.Build.targets" Condition=" '$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)../, Directory.Build.targets))' != '' " />
 </Project>