Use <TfmSpecificPackageFile> instead of <None> to add the lib placeholders to metapackages

Directory.Build.props

@@ -32,21 +32,19 @@
     <PublicKeyToken>35a561290d20de2f</PublicKeyToken>
   </PropertyGroup>
 
-  <!--
-    Note: when adding new targets, the OpenIddict, OpenIddict.AspNetCore and OpenIddict.Owin
-    metapackages MUST be updated to produce placeholder files for the added target frameworks.
-  -->
   <PropertyGroup>
     <NetFrameworkTargetFrameworks Condition=" '$(NetFrameworkTargetFrameworks)' == '' ">
       net461;
       net472;
       net48
     </NetFrameworkTargetFrameworks>
+
     <NetCoreTargetFrameworks Condition=" '$(NetCoreTargetFrameworks)' == '' ">
       net6.0;
       net7.0;
       net8.0
     </NetCoreTargetFrameworks>
+
     <NetCoreWindowsTargetFrameworks Condition=" '$(NetCoreWindowsTargetFrameworks)' == '' ">
       net6.0-windows7.0;
       net6.0-windows10.0.17763;
@@ -55,6 +53,7 @@
       net8.0-windows7.0;
       net8.0-windows10.0.17763
     </NetCoreWindowsTargetFrameworks>
+
     <NetStandardTargetFrameworks Condition=" '$(NetStandardTargetFrameworks)' == '' ">
       netstandard2.0;
       netstandard2.1
@@ -92,6 +91,7 @@
     <WarnOnPackingNonPackableProject>false</WarnOnPackingNonPackableProject>
     <CheckEolTargetFramework>false</CheckEolTargetFramework>
     <AfterTargetFrameworkInferenceTargets>$(MSBuildThisFileDirectory)eng\AfterTargetFrameworkInference.targets</AfterTargetFrameworkInferenceTargets>
+    <TargetsForTfmSpecificContentInPackage>$(TargetsForTfmSpecificContentInPackage);AddTfmSpecificPlaceholders</TargetsForTfmSpecificContentInPackage>
   </PropertyGroup>
 
   <!--

Directory.Build.targets

@@ -136,7 +136,24 @@
                 ('$(TargetFrameworkIdentifier)' == '.NETFramework') ">
     <DefineConstants>$(DefineConstants);SUPPORTS_WINDOWS_RUNTIME</DefineConstants>
   </PropertyGroup>
-  
+
+  <!--
+    Note: metapackages don't include any build output. To ensure the TFM-specific folders under
+    /lib are preserved, a placeholder file is added for each supported target framework moniker.
+  -->
+
+  <Target Name="AddTfmSpecificPlaceholders" Condition=" '$(IncludeBuildOutput)' != 'true' ">
+    <GetNuGetShortFolderName TargetFrameworkMoniker="$(TargetFrameworkMoniker)"
+                             TargetPlatformMoniker="$(TargetPlatformMoniker)">
+      <Output TaskParameter="NuGetShortFolderName" PropertyName="_NuGetShortFolderName" />
+    </GetNuGetShortFolderName>
+
+    <ItemGroup>
+      <TfmSpecificPackageFile Include="$(MSBuildThisFileDirectory)eng\_._"
+                              PackagePath="lib\$(_NuGetShortFolderName)\_._" />
+    </ItemGroup>
+  </Target>
+
   <!--
     Note: Arcade always generates .resx backing files with internal static methods/constants.
     To ensure the OpenIddict resources are public, the default visibility is manually overridden.

OpenIddict.sln

@@ -66,6 +66,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "eng", "eng", "{6E8E862C-3F2
 		eng\Tools.props = eng\Tools.props
 		eng\Version.Details.xml = eng\Version.Details.xml
 		eng\Versions.props = eng\Versions.props
+		eng\_._ = eng\_._
 	EndProjectSection
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "root", "root", "{F6F3C8E0-BBD7-41A5-9E20-385DC185DBC0}"

src/OpenIddict.AspNetCore/OpenIddict.AspNetCore.csproj

@@ -22,13 +22,4 @@
     <ProjectReference Include="..\OpenIddict.Validation.DataProtection\OpenIddict.Validation.DataProtection.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <None Include="_._" Pack="true" PackagePath="lib\net461\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net472\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net48\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net6.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net7.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net8.0\_._" />
-  </ItemGroup>
-
 </Project>

src/OpenIddict.Owin/OpenIddict.Owin.csproj

@@ -19,10 +19,4 @@
     <ProjectReference Include="..\OpenIddict.Validation.Owin\OpenIddict.Validation.Owin.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <None Include="_._" Pack="true" PackagePath="lib\net461\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net472\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net48\_._" />
-  </ItemGroup>
-
 </Project>

src/OpenIddict.Owin/_._

@@ -1 +0,0 @@
-

src/OpenIddict/OpenIddict.csproj

@@ -34,22 +34,4 @@ To use these features on ASP.NET Core or OWIN/Katana/ASP.NET 4.x, reference the
     <ProjectReference Include="..\OpenIddict.Validation.SystemNetHttp\OpenIddict.Validation.SystemNetHttp.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <None Include="_._" Pack="true" PackagePath="lib\net461\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net472\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net48\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net6.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net6.0-windows7.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net6.0-windows10.0.17763\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net7.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net7.0-windows7.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net7.0-windows10.0.17763\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net8.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net8.0-windows7.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\net8.0-windows10.0.17763\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\netstandard2.0\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\netstandard2.1\_._" />
-    <None Include="_._" Pack="true" PackagePath="lib\uap10.0.17763\_._" />
-  </ItemGroup>
-
 </Project>

src/OpenIddict/_._

@@ -1 +0,0 @@
-