Allow trimming out incompatible ProjectReferences

src/Microsoft.DotNet.Build.Tasks.TargetFramework/src/ChooseBestP2PTargetFrameworkTask.cs

@@ -3,37 +3,36 @@
 
 using Microsoft.Build.Framework;
 using System;
+using System.Collections.Generic;
 using System.IO;
 
 namespace Microsoft.DotNet.Build.Tasks.TargetFramework
 {
     public class ChooseBestP2PTargetFrameworkTask : BuildTask
     {
-        [Required]
-        public string TargetFramework { get; set; }
-
         [Required]
         public ITaskItem[] ProjectReferencesWithTargetFrameworks { get; set; }
 
         [Required]
         public string RuntimeGraph { get; set; }
 
+        [Required]
+        public string TargetFramework { get; set; }
+
+        public bool OmitIncompatibleProjectReferences { get; set; }
+
         [Output]
         public ITaskItem[] AnnotatedProjectReferencesWithSetTargetFramework { get; set; }
 
         public override bool Execute()
         {
-            AnnotatedProjectReferencesWithSetTargetFramework = new ITaskItem[ProjectReferencesWithTargetFrameworks.Length];
+            var annotatedProjectReferencesWithSetTargetFramework = new List<ITaskItem>(ProjectReferencesWithTargetFrameworks.Length);
             var targetFrameworkResolver = new TargetFrameworkResolver(RuntimeGraph);
 
             for (int i = 0; i < ProjectReferencesWithTargetFrameworks.Length; i++)
             {
                 ITaskItem projectReference = ProjectReferencesWithTargetFrameworks[i];
-                string targetFrameworksValue = projectReference.GetMetadata("RawTargetFrameworks");
-                if (string.IsNullOrEmpty(targetFrameworksValue))
-                {
-                    targetFrameworksValue = projectReference.GetMetadata("TargetFrameworks");
-                }
+                string targetFrameworksValue = projectReference.GetMetadata("TargetFrameworks");
 
                 // Allow referencing projects with TargetFrameworks explicitely cleared out, i.e. Microsoft.Build.Traversal.
                 if (!string.IsNullOrWhiteSpace(targetFrameworksValue))
@@ -49,6 +48,10 @@ public override bool Execute()
                     string bestTargetFramework = targetFrameworkResolver.GetBestSupportedTargetFramework(targetFrameworks, referringTargetFramework);
                     if (bestTargetFramework == null)
                     {
+                        if (OmitIncompatibleProjectReferences)
+                        {
+                            continue;
+                        }
                         Log.LogError($"Not able to find a compatible supported target framework for {referringTargetFramework} in Project {Path.GetFileName(projectReference.ItemSpec)}. The Supported Configurations are {string.Join(", ", targetFrameworks)}");
                     }
 
@@ -74,9 +77,10 @@ public override bool Execute()
                     projectReference.SetMetadata("SkipGetTargetFrameworkProperties", "true");
                 }
 
-                AnnotatedProjectReferencesWithSetTargetFramework[i] = projectReference;
+                annotatedProjectReferencesWithSetTargetFramework.Add(projectReference);
             }
 
+            AnnotatedProjectReferencesWithSetTargetFramework = annotatedProjectReferencesWithSetTargetFramework.ToArray();
             return !Log.HasLoggedErrors;
         }        
     }

src/Microsoft.DotNet.Build.Tasks.TargetFramework/src/build/Microsoft.DotNet.Build.Tasks.TargetFramework.props

@@ -1,12 +1,5 @@
 <!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. -->
 <Project>
-  <!-- Add unparsed TargetFrameworks property to GetTargetFrameworks return item metadata to read from it later. -->
-  <ItemDefinitionGroup>
-    <_ThisProjectBuildMetadata>
-      <RawTargetFrameworks>$(TargetFrameworks)</RawTargetFrameworks>
-    </_ThisProjectBuildMetadata>
-  </ItemDefinitionGroup>
-
   <PropertyGroup>
     <DotNetBuildTasksTargetFrameworkAssembly Condition="'$(MSBuildRuntimeType)' == 'core'">..\tools\netcoreapp3.1\Microsoft.DotNet.Build.Tasks.TargetFramework.dll</DotNetBuildTasksTargetFrameworkAssembly>
     <DotNetBuildTasksTargetFrameworkAssembly Condition="'$(MSBuildRuntimeType)' != 'core'">..\tools\net472\Microsoft.DotNet.Build.Tasks.TargetFramework.dll</DotNetBuildTasksTargetFrameworkAssembly>

src/Microsoft.DotNet.Build.Tasks.TargetFramework/src/build/Microsoft.DotNet.Build.Tasks.TargetFramework.targets

@@ -23,9 +23,10 @@
       <_ProjectReferenceWithTargetFrameworks Include="@(ProjectReference->WithMetadataValue('SkipGetTargetFrameworkProperties', 'true'))" />
     </ItemGroup>
 
-    <ChooseBestP2PTargetFrameworkTask TargetFramework="$(TargetFramework)"
-                                      ProjectReferencesWithTargetFrameworks="@(_ProjectReferenceWithTargetFrameworks)"
-                                      RuntimeGraph="$(RuntimeGraph)">
+    <ChooseBestP2PTargetFrameworkTask ProjectReferencesWithTargetFrameworks="@(_ProjectReferenceWithTargetFrameworks)"
+                                      RuntimeGraph="$(RuntimeGraph)"
+                                      TargetFramework="$(TargetFramework)"
+                                      OmitIncompatibleProjectReferences="$(OmitIncompatibleProjectReferences)">
       <Output TaskParameter="AnnotatedProjectReferencesWithSetTargetFramework" ItemName="_ProjectReferenceWithBestTargetFramework" />
     </ChooseBestP2PTargetFrameworkTask>