Fix building projects restored with NuGet 5.7

src/Tasks/Microsoft.NET.Build.Tasks/LockFileExtensions.cs

@@ -13,25 +13,39 @@ namespace Microsoft.NET.Build.Tasks
 {
     internal static class LockFileExtensions
     {
-        public static LockFileTarget GetTargetAndThrowIfNotFound(this LockFile lockFile, string frameworkAlias, string runtime)
+        public static LockFileTarget GetTargetAndReturnNullIfNotFound(this LockFile lockFile, string frameworkAlias, string runtimeIdentifier)
         {
-            LockFileTarget lockFileTarget = lockFile.GetTarget(frameworkAlias, runtime);
+            LockFileTarget lockFileTarget = lockFile.GetTarget(frameworkAlias, runtimeIdentifier);
+
+            if (lockFileTarget == null &&
+                lockFile.PackageSpec.TargetFrameworks.All(tfi => string.IsNullOrEmpty(tfi.TargetAlias)))
+            {
+                var nuGetFramework = NuGetUtils.ParseFrameworkName(frameworkAlias);
+                lockFileTarget = lockFile.GetTarget(nuGetFramework, runtimeIdentifier);
+            }
+
+            return lockFileTarget;
+        }
+
+        public static LockFileTarget GetTargetAndThrowIfNotFound(this LockFile lockFile, string frameworkAlias, string runtimeIdentifier)
+        {
+            LockFileTarget lockFileTarget = lockFile.GetTargetAndReturnNullIfNotFound(frameworkAlias, runtimeIdentifier);
 
             if (lockFileTarget == null)
             {
                 string frameworkString = frameworkAlias;
-                string targetMoniker = string.IsNullOrEmpty(runtime) ?
+                string targetMoniker = string.IsNullOrEmpty(runtimeIdentifier) ?
                     frameworkString :
-                    $"{frameworkString}/{runtime}";
+                    $"{frameworkString}/{runtimeIdentifier}";
 
                 string message;
-                if (string.IsNullOrEmpty(runtime))
+                if (string.IsNullOrEmpty(runtimeIdentifier))
                 {
                     message = string.Format(Strings.AssetsFileMissingTarget, lockFile.Path, targetMoniker, frameworkString);
                 }
                 else
                 {
-                    message = string.Format(Strings.AssetsFileMissingRuntimeIdentifier, lockFile.Path, targetMoniker, frameworkString, runtime);
+                    message = string.Format(Strings.AssetsFileMissingRuntimeIdentifier, lockFile.Path, targetMoniker, frameworkString, runtimeIdentifier);
                 }
 
                 throw new BuildErrorException(message);

src/Tasks/Microsoft.NET.Build.Tasks/ResolvePackageAssets.cs

@@ -663,8 +663,8 @@ public CacheWriter(ResolvePackageAssets task)
                 CanWriteToCacheFile = true;
                 if (task.DesignTimeBuild)
                 {
-                    _compileTimeTarget = _lockFile.GetTarget(_targetFramework, runtimeIdentifier: null);
-                    _runtimeTarget = _lockFile.GetTarget(_targetFramework, _task.RuntimeIdentifier);
+                    _compileTimeTarget = _lockFile.GetTargetAndReturnNullIfNotFound(_targetFramework, runtimeIdentifier: null);
+                    _runtimeTarget = _lockFile.GetTargetAndReturnNullIfNotFound(_targetFramework, _task.RuntimeIdentifier);
                     if (_compileTimeTarget == null)
                     {
                         _compileTimeTarget = new LockFileTarget();
@@ -678,7 +678,7 @@ public CacheWriter(ResolvePackageAssets task)
                 }
                 else
                 {
-                    _compileTimeTarget = _lockFile.GetTargetAndThrowIfNotFound(_targetFramework, runtime: null); 
+                    _compileTimeTarget = _lockFile.GetTargetAndThrowIfNotFound(_targetFramework, runtimeIdentifier: null); 
                     _runtimeTarget = _lockFile.GetTargetAndThrowIfNotFound(_targetFramework, _task.RuntimeIdentifier);
                 }
 
@@ -1065,7 +1065,7 @@ private void WriteApphostsForShimRuntimeIdentifiers()
                     LockFileTarget runtimeTarget;
                     if (_task.DesignTimeBuild)
                     {
-                        runtimeTarget = _lockFile.GetTarget(_targetFramework, runtimeIdentifier) ?? new LockFileTarget();
+                        runtimeTarget = _lockFile.GetTargetAndReturnNullIfNotFound(_targetFramework, runtimeIdentifier) ?? new LockFileTarget();
                     }
                     else
                     {
@@ -1095,7 +1095,7 @@ private bool CanResolveApphostFromFrameworkReference()
                 }
                 else
                 { 
-                    var targetFramework = _lockFile.GetTarget(_targetFramework, null).TargetFramework;
+                    var targetFramework = _lockFile.GetTargetAndThrowIfNotFound(_targetFramework, null).TargetFramework;
 
                     if (targetFramework.Version.Major >= 3
                         && targetFramework.Framework.Equals(".NETCoreApp", StringComparison.OrdinalIgnoreCase))

src/Tests/Microsoft.NET.Restore.Tests/RestoreWithOlderNuGet.cs

@@ -0,0 +1,50 @@
+// 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 FluentAssertions;
+using Microsoft.NET.TestFramework;
+using Microsoft.NET.TestFramework.Assertions;
+using Microsoft.NET.TestFramework.Commands;
+using Microsoft.NET.TestFramework.ProjectConstruction;
+using NuGet.Common;
+using NuGet.Packaging;
+using NuGet.Packaging.Core;
+using System.IO;
+using System.Threading;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.NET.Restore.Tests
+{
+    public class RestoreWithOlderNuGet : SdkTest
+    {
+        public RestoreWithOlderNuGet(ITestOutputHelper log) : base(log)
+        {
+        }
+
+        [Fact]
+        public void ItCanBuildProjectRestoredWithNuGet5_7()
+        {
+            var testProject = new TestProject()
+            {
+                TargetFrameworks = "netcoreapp3.1",
+                IsSdkProject = true
+            };
+            testProject.PackageReferences.Add(new TestPackageReference("Humanizer.Core", "2.8.26"));
+
+            var testAsset = _testAssetsManager.CreateTestProject(testProject);
+
+            var restoreCommand = new NuGetExeRestoreCommand(Log, testAsset.Path, testProject.Name);
+            restoreCommand.NuGetExeVersion = "5.7.0";
+            restoreCommand.Execute()
+                .Should()
+                .Pass();
+
+            new BuildCommand(testAsset)
+                .ExecuteWithoutRestore()
+                .Should()
+                .Pass();
+        }
+    }
+}

src/Tests/Microsoft.NET.TestFramework/Commands/NuGetExeRestoreCommand.cs

@@ -18,6 +18,8 @@ public class NuGetExeRestoreCommand : TestCommand
 
         public string ProjectFile { get; }
 
+        public string NuGetExeVersion { get; set; }
+
         public string FullPathProjectFile => Path.Combine(ProjectRootPath, ProjectFile);
 
         public NuGetExeRestoreCommand(ITestOutputHelper log, string projectRootPath, string relativePathToProject = null) : base(log)
@@ -43,19 +45,36 @@ protected override SdkCommandSpec CreateCommand(IEnumerable<string> args)
             {
                 throw new InvalidOperationException("Path to nuget.exe not set");
             }
-            else if (!File.Exists(TestContext.Current.NuGetExePath))
+
+            var nugetExePath = TestContext.Current.NuGetExePath;
+            if (!string.IsNullOrEmpty(NuGetExeVersion))
             {
-                //  https://dist.nuget.org/win-x86-commandline/latest/nuget.exe
+                nugetExePath = Path.Combine(Path.GetDirectoryName(nugetExePath), NuGetExeVersion, "nuget.exe");
+            }
+
+            if (!File.Exists(nugetExePath))
+            {
+                string directory = Path.GetDirectoryName(nugetExePath);
+                if (!Directory.Exists(directory))
+                {
+                    Directory.CreateDirectory(directory);
+                }
+
+                string url = string.IsNullOrEmpty(NuGetExeVersion) ?
+                    "https://dist.nuget.org/win-x86-commandline/latest/nuget.exe" :
+                    $"https://dist.nuget.org/win-x86-commandline/v{NuGetExeVersion}/nuget.exe";
                 var client = new System.Net.WebClient();
-                client.DownloadFile("https://dist.nuget.org/win-x86-commandline/latest/nuget.exe", TestContext.Current.NuGetExePath);
+                client.DownloadFile(url, nugetExePath);
             }
 
             var ret = new SdkCommandSpec()
             {
-                FileName = TestContext.Current.NuGetExePath,
+                FileName = nugetExePath,
                 Arguments = newArgs
             };
 
+            TestContext.Current.AddTestEnvironmentVariables(ret);
+
             return ret;
         }
     }