Fixed netcore50 package based frameworks (#2630)

TestAssets/TestProjects/TestMicrosoftCSharpReferenceMissingFramework/project.json

@@ -8,6 +8,11 @@
         "Microsoft.NETCore.App": "1.0.0-rc2-*"
       }
     },
+    "netcore50": {
+      "dependencies": {
+        "System.Private.Uri": "4.0.1-rc2-24018"
+      }
+    },
     "net99": {
       "dependencies": {
         "Microsoft.CSharp": "4.0.1-rc2-24018"

src/Microsoft.DotNet.ProjectModel/ProjectContextBuilder.cs

@@ -380,7 +380,7 @@ namespace Microsoft.DotNet.ProjectModel
                 if (package != null && 
                     package.Resolved && 
                     package.HasCompileTimePlaceholder && 
-                    !TargetFramework.IsPackageBased)
+                    !TargetFramework.IsPackageBased())
                 {
                     var newKey = new LibraryKey(library.Identity.Name, LibraryType.ReferenceAssembly);
                     var dependency = new LibraryRange(library.Identity.Name, LibraryType.ReferenceAssembly);

src/Microsoft.DotNet.ProjectModel/Utilities/FrameworksExtensions.cs

@@ -1,7 +1,7 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-using System.Linq;
+using System;
 using System.Runtime.Versioning;
 
 namespace NuGet.Frameworks
@@ -56,5 +56,12 @@ namespace NuGet.Frameworks
             }
             return name + "-" + frameworkName.Profile;
         }
+        
+        public static bool IsPackageBased(this NuGetFramework self)
+        {
+            return self.IsPackageBased ||
+                    (self.Framework == FrameworkConstants.FrameworkIdentifiers.NetCore &&
+                     self.Version >= new Version(5, 0, 0, 0));
+        }
     }
 }

test/Microsoft.DotNet.ProjectModel.Tests/PackageDependencyProviderTests.cs

@@ -76,7 +76,22 @@ namespace Microsoft.DotNet.ProjectModel.Tests
                                                      .WithTargetFramework("net99")
                                                      .Build();
 
+            // Will fail with dupes if any
             context.LibraryManager.GetLibraries().ToDictionary(l => l.Identity.Name);
         }
+        
+        [Fact]
+        public void NetCore50ShouldNotResolveFrameworkAssemblies()
+        {
+            var instance = TestAssetsManager.CreateTestInstance("TestMicrosoftCSharpReferenceMissingFramework")
+                                            .WithLockFiles();
+
+            var context = new ProjectContextBuilder().WithProjectDirectory(instance.TestRoot)
+                                                     .WithTargetFramework("netcore50")
+                                                     .Build();
+
+            var diagnostics = context.LibraryManager.GetAllDiagnostics();
+            Assert.False(diagnostics.Any(d => d.ErrorCode == ErrorCodes.DOTNET1011));
+        }
     }
 }