Improve error messages when project hasn't been restored for the right target framework or runtime identifier

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

@@ -0,0 +1,32 @@
+// 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 Microsoft.Build.Framework;
+using NuGet.ProjectModel;
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.NET.Build.Tasks
+{
+    public class CheckForTargetInAssetsFile : TaskBase
+    {
+        [Required]
+        public string AssetsFilePath { get; set; }
+
+        [Required]
+        public string TargetFrameworkMoniker { get; set; }
+
+        public string RuntimeIdentifier { get; set; }
+
+
+        protected override void ExecuteCore()
+        {
+            LockFile lockFile = new LockFileCache(BuildEngine4).GetLockFile(AssetsFilePath);
+
+            var nugetFramework = NuGetUtils.ParseFrameworkName(TargetFrameworkMoniker);
+
+            lockFile.GetTargetAndThrowIfNotFound(nugetFramework, RuntimeIdentifier);
+        }
+    }
+}

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

@@ -12,6 +12,33 @@ namespace Microsoft.NET.Build.Tasks
 {
     internal static class LockFileExtensions
     {
+        public static LockFileTarget GetTargetAndThrowIfNotFound(this LockFile lockFile, NuGetFramework framework, string runtime)
+        {
+            LockFileTarget lockFileTarget = lockFile.GetTarget(framework, runtime);
+
+            if (lockFileTarget == null)
+            {
+                string frameworkString = framework.DotNetFrameworkName;
+                string targetMoniker = string.IsNullOrEmpty(runtime) ?
+                    frameworkString :
+                    $"{frameworkString}/{runtime}";
+
+                string message;
+                if (string.IsNullOrEmpty(runtime))
+                {
+                    message = string.Format(Strings.AssetsFileMissingTarget, lockFile.Path, targetMoniker, framework.GetShortFolderName());
+                }
+                else
+                {
+                    message = string.Format(Strings.AssetsFileMissingRuntimeIdentifier, lockFile.Path, targetMoniker, framework.GetShortFolderName(), runtime);
+                }
+
+                throw new BuildErrorException(message);
+            }
+
+            return lockFileTarget;
+        }
+
         public static ProjectContext CreateProjectContext(
             this LockFile lockFile,
             NuGetFramework framework,
@@ -28,17 +55,7 @@ public static ProjectContext CreateProjectContext(
                 throw new ArgumentNullException(nameof(framework));
             }
 
-            LockFileTarget lockFileTarget = lockFile.GetTarget(framework, runtime);
-
-            if (lockFileTarget == null)
-            {
-                string frameworkString = framework.DotNetFrameworkName;
-                string targetMoniker = string.IsNullOrEmpty(runtime) ?
-                    frameworkString :
-                    $"{frameworkString}/{runtime}";
-
-                throw new BuildErrorException(Strings.AssetsFileMissingTarget, lockFile.Path, targetMoniker, framework.GetShortFolderName(), runtime);
-            }
+            var lockFileTarget = lockFile.GetTargetAndThrowIfNotFound(framework, runtime);
 
             LockFileTargetLibrary platformLibrary = lockFileTarget.GetLibrary(platformLibraryName);
             bool isFrameworkDependent = platformLibrary != null && (!isSelfContained || string.IsNullOrEmpty(lockFileTarget.RuntimeIdentifier));

src/Tasks/Microsoft.NET.Build.Tasks/Microsoft.NET.Build.Tasks.csproj

@@ -47,8 +47,8 @@
       <DependentUpon>Strings.resx</DependentUpon>
     </EmbeddedResource>
     <Compile Update="Resources\Strings.Designer.cs">
-      <DesignTime>true</DesignTime>
-      <AutoGen>true</AutoGen>
+      <DesignTime>True</DesignTime>
+      <AutoGen>True</AutoGen>
       <DependentUpon>Strings.resx</DependentUpon>
     </Compile>
   </ItemGroup>

src/Tasks/Microsoft.NET.Build.Tasks/Resources/Strings.resx

@@ -130,7 +130,7 @@
     <value>Assets file '{0}' not found. Run a NuGet package restore to generate this file.</value>
   </data>
   <data name="AssetsFileMissingTarget" xml:space="preserve">
-    <value>Assets file '{0}' doesn't have a target for '{1}'. Ensure you have restored this project for TargetFramework='{2}' and RuntimeIdentifier='{3}'.</value>
+    <value>Assets file '{0}' doesn't have a target for '{1}'. Ensure you have included '{2}' in the TargetFrameworks for your project.</value>
   </data>
   <data name="AssetsFilePathNotRooted" xml:space="preserve">
     <value>Assets file path '{0}' is not rooted. Only full paths are supported.</value>
@@ -297,4 +297,7 @@
   <data name="UnsupportedTargetFrameworkVersion" xml:space="preserve">
     <value>The current .NET SDK does not support targeting {0} {1}.  Either target {0} {2} or lower, or use a version of the .NET SDK that supports {0} {1}.</value>
   </data>
+  <data name="AssetsFileMissingRuntimeIdentifier" xml:space="preserve">
+    <value>Assets file '{0}' doesn't have a target for '{1}'. Ensure you have included '{2}' in the TargetFrameworks for your project. You may also need to include '{3}' in your project's RuntimeIdentifiers.</value>
+  </data>
 </root>

src/Tasks/Microsoft.NET.Build.Tasks/build/Microsoft.PackageDependencyResolution.targets

@@ -145,13 +145,24 @@ Copyright (c) .NET Foundation. All rights reserved.
 
   <UsingTask TaskName="Microsoft.NET.Build.Tasks.ResolvePackageDependencies"
              AssemblyFile="$(MicrosoftNETBuildTasksAssembly)" />
+  <UsingTask TaskName="Microsoft.NET.Build.Tasks.CheckForTargetInAssetsFile"
+           AssemblyFile="$(MicrosoftNETBuildTasksAssembly)" />
 
   <!-- The condition on this target causes it to be skipped during design-time builds if
         the restore operation hasn't run yet.  This is to avoid displaying an error in
         the Visual Studio error list when a project is created before NuGet restore has
         run and created the assets file. -->
   <Target Name="RunResolvePackageDependencies"
           Condition=" '$(DesignTimeBuild)' != 'true' Or Exists('$(ProjectAssetsFile)')">
+
+    <!-- Verify that the assets file has a target for the right framework.  Otherwise, if we restored for the
+         wrong framework, we'd end up finding no references to pass to the compiler, and we'd get a ton of
+         compile errors. -->
+    <CheckForTargetInAssetsFile
+      AssetsFilePath="$(ProjectAssetsFile)"
+      TargetFrameworkMoniker="$(TargetFrameworkMoniker)"
+      RuntimeIdentifier="$(RuntimeIdentifier)" />
+
     <ResolvePackageDependencies
       ProjectPath="$(MSBuildProjectFullPath)"
       ProjectAssetsFile="$(ProjectAssetsFile)"

test/Microsoft.NET.Build.Tests/GivenThatWeWantToBuildALibrary.cs

@@ -17,6 +17,9 @@
 using System.Runtime.CompilerServices;
 using Xunit.Abstractions;
 using Microsoft.NET.TestFramework.ProjectConstruction;
+using NuGet.ProjectModel;
+using NuGet.Common;
+using Newtonsoft.Json.Linq;
 
 namespace Microsoft.NET.Build.Tests
 {
@@ -591,19 +594,46 @@ public void It_fails_to_build_if_targeting_a_higher_framework_than_is_supported(
         [Fact]
         public void It_passes_ridless_target_to_compiler()
         {
-            var testAsset = _testAssetsManager
-                .CopyTestAsset("AppWithLibrary", "RidlessLib")
-                .WithSource()
-                .Restore(Log, relativePath: "TestLibrary");
+            var runtimeIdentifier = EnvironmentInfo.GetCompatibleRid("netcoreapp2.0");
 
-            var libraryProjectDirectory = Path.Combine(testAsset.TestRoot, "TestLibrary");
-            var fullPathProjectFile = new BuildCommand(Log, libraryProjectDirectory).FullPathProjectFile;
+            var testProject = new TestProject()
+            {
+                Name = "CompileDoesntUseRid",
+                TargetFrameworks = "netcoreapp2.0",
+                RuntimeIdentifier = runtimeIdentifier,
+                IsSdkProject = true
+            };
+
+            var testAsset = _testAssetsManager.CreateTestProject(testProject, testProject.Name)
+                .WithProjectChanges(project =>
+                {
+                    //  Set property to disable logic in Microsoft.NETCore.App package that will otherwise cause a failure
+                    //  when we remove everything under the rid-specific targets in the assets file
+                    var ns = project.Root.Name.Namespace;
+                    project.Root.Element(ns + "PropertyGroup")
+                        .Add(new XElement(ns + "EnsureNETCoreAppRuntime", false));
+                })
+                .Restore(Log, testProject.Name);
+
+            var buildCommand = new BuildCommand(Log, testAsset.TestRoot, testProject.Name);
+
+            //  Test that compilation doesn't depend on any rid-specific assets by removing them from the assets file after it's been restored
+            var assetsFilePath = Path.Combine(buildCommand.GetBaseIntermediateDirectory().FullName, "project.assets.json");
+
+            JObject assetsContents = JObject.Parse(File.ReadAllText(assetsFilePath));
+            foreach (JProperty target in assetsContents["targets"])
+            {
+                if (target.Name.Contains("/"))
+                {
+                    //  This is a target element with a RID specified, so remove all its contents
+                    target.Value = new JObject();
+                }
+            }
+            string newContents = assetsContents.ToString();
+            File.WriteAllText(assetsFilePath, newContents);
 
-            // compile should still pass with unknown RID because references are always pulled 
-            // from RIDLess target
-            var buildCommand = new MSBuildCommand(Log, "Compile", fullPathProjectFile);
             buildCommand
-                .Execute("/p:RuntimeIdentifier=unkownrid")
+                .Execute()
                 .Should()
                 .Pass();
         }