Use MSBuildProjectExtensionsPath for RestoreOutputPath

src/NuGet.Clients/NuGet.CommandLine/Common/CommandLineResponseFile.cs

@@ -126,13 +126,13 @@ private static string[] SplitArgs(string unsplitArguments)
         {
             if (string.IsNullOrWhiteSpace(unsplitArguments))
             {
-                return new string[0];
+                return Array.Empty<string>();
             }
 
             var ptrToSplitArgs = CommandLineToArgvW(unsplitArguments, out int numberOfArgs);
             if (ptrToSplitArgs == IntPtr.Zero)
             {
-                return new string[0];
+                return Array.Empty<string>();
             }
 
             try

src/NuGet.Clients/NuGet.PackageManagement.VisualStudio/Projects/LegacyPackageReferenceProject.cs

@@ -79,7 +79,7 @@ public override async Task<string> GetAssetsFilePathAsync()
         public override async Task<string> GetCacheFilePathAsync()
         {
             await _threadingService.JoinableTaskFactory.SwitchToMainThreadAsync();
-            return NoOpRestoreUtilities.GetProjectCacheFilePath(cacheRoot: GetBaseIntermediatePath(), projectPath: _projectFullPath);
+            return NoOpRestoreUtilities.GetProjectCacheFilePath(cacheRoot: GetMSBuildProjectExtensionsPath(), projectPath: _projectFullPath);
         }
 
         public override async Task<string> GetAssetsFilePathOrNullAsync()
@@ -91,7 +91,7 @@ private async Task<string> GetAssetsFilePathAsync(bool shouldThrow)
         {
             await _threadingService.JoinableTaskFactory.SwitchToMainThreadAsync();
 
-            var baseIntermediatePath = GetBaseIntermediatePath(shouldThrow);
+            var baseIntermediatePath = GetMSBuildProjectExtensionsPath(shouldThrow);
 
             if (baseIntermediatePath == null)
             {
@@ -164,25 +164,25 @@ public override async Task<bool> UninstallPackageAsync(
 
         #endregion
 
-        private string GetBaseIntermediatePath(bool shouldThrow = true)
+        private string GetMSBuildProjectExtensionsPath(bool shouldThrow = true)
         {
             ThreadHelper.ThrowIfNotOnUIThread();
 
-            var baseIntermediatePath = _vsProjectAdapter.BaseIntermediateOutputPath;
+            var msbuildProjectExtensionsPath = _vsProjectAdapter.MSBuildProjectExtensionsPath;
 
-            if (string.IsNullOrEmpty(baseIntermediatePath))
+            if (string.IsNullOrEmpty(msbuildProjectExtensionsPath))
             {
                 if (shouldThrow)
                 {
                     throw new InvalidDataException(string.Format(
-                        Strings.BaseIntermediateOutputPathNotFound,
+                        Strings.MSBuildProjectExtensionsPathNotFound,
                         _vsProjectAdapter.ProjectDirectory));
                 }
 
                 return null;
             }
 
-            return baseIntermediatePath;
+            return msbuildProjectExtensionsPath;
         }
 
         private string GetPackagesPath(ISettings settings)
@@ -337,7 +337,7 @@ private async Task<PackageSpec> GetPackageSpecAsync(ISettings settings)
                 RestoreMetadata = new ProjectRestoreMetadata
                 {
                     ProjectStyle = ProjectStyle.PackageReference,
-                    OutputPath = GetBaseIntermediatePath(),
+                    OutputPath = GetMSBuildProjectExtensionsPath(),
                     ProjectPath = _projectFullPath,
                     ProjectName = projectName,
                     ProjectUniqueName = _projectFullPath,

src/NuGet.Clients/NuGet.PackageManagement.VisualStudio/Projects/VsProjectAdapter.cs

@@ -35,18 +35,18 @@ internal class VsProjectAdapter : IVsProjectAdapter
 
         #region Properties
 
-        public string BaseIntermediateOutputPath
+        public string MSBuildProjectExtensionsPath
         {
             get
             {
-                var baseIntermediateOutputPath = BuildProperties.GetPropertyValue(ProjectBuildProperties.BaseIntermediateOutputPath);
+                var msbuildProjectExtensionsPath = BuildProperties.GetPropertyValue(ProjectBuildProperties.MSBuildProjectExtensionsPath);
 
-                if (string.IsNullOrEmpty(baseIntermediateOutputPath))
+                if (string.IsNullOrEmpty(msbuildProjectExtensionsPath))
                 {
                     return null;
                 }
 
-                return Path.Combine(ProjectDirectory, baseIntermediateOutputPath);
+                return Path.Combine(ProjectDirectory, msbuildProjectExtensionsPath);
             }
         }
 
@@ -278,7 +278,7 @@ public async Task<string[]> GetProjectTypeGuidsAsync()
                     return new string[] { _projectTypeGuid };
                 }
 
-                return new string[0];
+                return Array.Empty<string>();
             }
         }
 

src/NuGet.Clients/NuGet.PackageManagement.VisualStudio/Projects/VsProjectJsonNuGetProject.cs

@@ -39,23 +39,23 @@ public VsProjectJsonNuGetProject(
             ProjectServices = projectServices;
         }
 
-        protected override async Task<string> GetBaseIntermediatePathAsync()
+        protected override async Task<string> GetMSBuildProjectExtensionsPathAsync()
         {
-            var baseIntermediatePath = await ProjectServices.BuildProperties.GetPropertyValueAsync(ProjectBuildProperties.BaseIntermediateOutputPath);
+            var msbuildProjectExtensionsPath = await ProjectServices.BuildProperties.GetPropertyValueAsync(ProjectBuildProperties.MSBuildProjectExtensionsPath);
 
-            if (string.IsNullOrEmpty(baseIntermediatePath))
+            if (string.IsNullOrEmpty(msbuildProjectExtensionsPath))
             {
                 throw new InvalidDataException(string.Format(
-                    Strings.BaseIntermediateOutputPathNotFound,
+                    Strings.MSBuildProjectExtensionsPathNotFound,
                     MSBuildProjectPath));
             }
 
-            return UriUtility.GetAbsolutePathFromFile(MSBuildProjectPath, baseIntermediatePath);
+            return UriUtility.GetAbsolutePathFromFile(MSBuildProjectPath, msbuildProjectExtensionsPath);
         }
 
         public override async Task<string> GetCacheFilePathAsync()
         {
-            return NoOpRestoreUtilities.GetProjectCacheFilePath(await GetBaseIntermediatePathAsync(), MSBuildProjectPath);
+            return NoOpRestoreUtilities.GetProjectCacheFilePath(await GetMSBuildProjectExtensionsPathAsync(), MSBuildProjectPath);
         }
 
         protected override async Task UpdateInternalTargetFrameworkAsync()

src/NuGet.Clients/NuGet.PackageManagement.VisualStudio/Strings.resx

@@ -200,8 +200,8 @@
   <data name="ProjectNotLoaded_RestoreFailed" xml:space="preserve">
     <value>The operation failed as details for project {0} could not be loaded.</value>
   </data>
-  <data name="BaseIntermediateOutputPathNotFound" xml:space="preserve">
-    <value>The BaseIntermediateOutputPath MSBuild property could not be found for project '{0}'.</value>
+  <data name="MSBuildProjectExtensionsPathNotFound" xml:space="preserve">
+    <value>The MSBuildProjectExtensionsPath MSBuild property could not be found for project '{0}'.</value>
     <comment>{0} is the full path to the project.</comment>
   </data>
   <data name="ProjectCouldNotBeCastedToBuildPropertyStorage" xml:space="preserve">

src/NuGet.Clients/NuGet.VisualStudio.Common/IVsProjectAdapter.cs

@@ -22,9 +22,9 @@ public interface IVsProjectAdapter
         string AssetTargetFallback { get; }
 
         /// <summary>
-        /// BaseIntermediateOutputPath project property (e.g. c:\projFoo\obj)
+        /// MSBuildProjectExtensionsPath project property (e.g. c:\projFoo\obj)
         /// </summary>
-        string BaseIntermediateOutputPath { get; }
+        string MSBuildProjectExtensionsPath { get; }
 
         IProjectBuildProperties BuildProperties { get; }
 

src/NuGet.Clients/NuGet.VisualStudio.Common/VsHierarchyUtility.cs

@@ -104,7 +104,7 @@ public static string[] GetProjectTypeGuids(IVsHierarchy hierarchy, string defaul
                 return new[] { defaultType };
             }
 
-            return new string[0];
+            return Array.Empty<string>();
         }
 
         /// <summary>

src/NuGet.Clients/NuGetConsole.Host.PowerShell/UnsupportedHost.cs

@@ -46,7 +46,7 @@ public string ActivePackageSource
 
         public string[] GetPackageSources()
         {
-            return new string[0];
+            return Array.Empty<string>();
         }
 
         public string DefaultProject
@@ -60,7 +60,7 @@ public void SetDefaultProjectIndex(int index)
 
         public string[] GetAvailableProjects()
         {
-            return new string[0];
+            return Array.Empty<string>();
         }
 
         public void SetDefaultRunspace()

src/NuGet.Core/NuGet.Build.Tasks.Pack/NuGet.Build.Tasks.Pack.targets

@@ -148,7 +148,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     </PropertyGroup>
     <PropertyGroup>
       <PackageOutputPath Condition=" '$(PackageOutputPath)' == '' ">$(OutputPath)</PackageOutputPath>
-      <RestoreOutputPath Condition=" '$(RestoreOutputPath)' == '' " >$(BaseIntermediateOutputPath)</RestoreOutputPath>
+      <RestoreOutputPath Condition=" '$(RestoreOutputPath)' == '' " >$(MSBuildProjectExtensionsPath)</RestoreOutputPath>
     </PropertyGroup>
 
     <ConvertToAbsolutePath Paths="$(NuspecOutputPath)">

src/NuGet.Core/NuGet.Build.Tasks/GetRestoreSettingsTask.cs

@@ -131,7 +131,7 @@ public override bool Execute()
                 // Sources
                 var currentSources = RestoreSettingsUtils.GetValue(
                     () => RestoreSourcesOverride?.Select(MSBuildRestoreUtility.FixSourcePath).Select(e => GetGlobalAbsolutePath(e)).ToArray(),
-                    () => MSBuildRestoreUtility.ContainsClearKeyword(RestoreSources) ? new string[0] : null,
+                    () => MSBuildRestoreUtility.ContainsClearKeyword(RestoreSources) ? Array.Empty<string>() : null,
                     () => RestoreSources?.Select(MSBuildRestoreUtility.FixSourcePath).Select(e => UriUtility.GetAbsolutePathFromFile(ProjectUniqueName, e)).ToArray(),
                     () => (new PackageSourceProvider(settings)).LoadPackageSources().Where(e => e.IsEnabled).Select(e => e.Source).ToArray());
 
@@ -148,7 +148,7 @@ public override bool Execute()
                 // Fallback folders
                 var currentFallbackFolders = RestoreSettingsUtils.GetValue(
                     () => RestoreFallbackFoldersOverride?.Select(e => GetGlobalAbsolutePath(e)).ToArray(),
-                    () => MSBuildRestoreUtility.ContainsClearKeyword(RestoreFallbackFolders) ? new string[0] : null,
+                    () => MSBuildRestoreUtility.ContainsClearKeyword(RestoreFallbackFolders) ? Array.Empty<string>() : null,
                     () => RestoreFallbackFolders?.Select(e => UriUtility.GetAbsolutePathFromFile(ProjectUniqueName, e)).ToArray(),
                     () => SettingsUtility.GetFallbackPackageFolders(settings).ToArray());
 

src/NuGet.Core/NuGet.Build.Tasks/NuGet.targets

@@ -414,6 +414,25 @@ Copyright (c) .NET Foundation. All rights reserved.
     </PropertyGroup>
   </Target>
 
+  <!--
+    ============================================================
+    EnableIntermediateOutputPathMismatchWarning
+    If using PackageReference, enable an MSBuild warning if BaseIntermediateOutputPath is set to something different
+    than MSBuildProjectExtensionsPath, because it may be unexpected that the assets and related files wouldn't be written
+    to the BaseIntermediateOutputPath.
+    ============================================================
+  -->
+
+  <Target Name="EnableIntermediateOutputPathMismatchWarning" DependsOnTargets="_GetRestoreProjectStyle"
+          BeforeTargets="_CheckForInvalidConfigurationAndPlatform"
+          Condition="'$(RestoreProjectStyle)' == 'PackageReference'">
+
+    <PropertyGroup Condition="'$(EnableBaseIntermediateOutputPathMismatchWarning)' == ''">
+      <EnableBaseIntermediateOutputPathMismatchWarning>true</EnableBaseIntermediateOutputPathMismatchWarning>
+    </PropertyGroup>
+
+  </Target>
+
   <!--
     ============================================================
     _GetRestoreTargetFrameworksOutput
@@ -569,7 +588,15 @@ Copyright (c) .NET Foundation. All rights reserved.
     Returns="@(_RestoreGraphEntry)">
 
     <!-- Determine the restore output path -->
-    <PropertyGroup Condition=" '$(PackageReferenceCompatibleProjectStyle)' == 'true' OR '$(RestoreProjectStyle)' == 'ProjectJson' ">
+    <PropertyGroup Condition=" '$(PackageReferenceCompatibleProjectStyle)' == 'true' ">
+      <!-- NuGet writes .props and .targets files to the RestoreOutputPath for PackageReference projects.  MSBuild common
+           targets import these via the MSBuildProjectExtensionsPath, so that's what the RestoreOutputPath should be. -->
+      <RestoreOutputPath Condition=" '$(RestoreOutputPath)' == '' " >$(MSBuildProjectExtensionsPath)</RestoreOutputPath>
+    </PropertyGroup>
+    <PropertyGroup Condition=" '$(RestoreProjectStyle)' == 'ProjectJson' ">
+      <!-- For project.json projects, only the assets file cache goes in the RestoreOutputPath.  The assets file and the
+           generated .props and .targets go in the project folder.  So in that case use the BaseIntermediateOutputPath,
+           so that the assets file cache will respect a BaseIntermediateOutputPath set in the project body. -->
       <RestoreOutputPath Condition=" '$(RestoreOutputPath)' == '' " >$(BaseIntermediateOutputPath)</RestoreOutputPath>
     </PropertyGroup>
 

src/NuGet.Core/NuGet.Build.Tasks/WarnForInvalidProjectsTask.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Linq;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
@@ -28,8 +29,8 @@ public override bool Execute()
             var log = new MSBuildLogger(Log);
 
             // item -> string
-            var all = AllProjects?.Select(e => e.ItemSpec).ToArray() ?? new string[0];
-            var valid = ValidProjects?.Select(e => e.ItemSpec).ToArray() ?? new string[0];
+            var all = AllProjects?.Select(e => e.ItemSpec).ToArray() ?? Array.Empty<string>();
+            var valid = ValidProjects?.Select(e => e.ItemSpec).ToArray() ?? Array.Empty<string>();
 
             // log inputs
             BuildTasksUtility.LogInputParam(log, nameof(AllProjects), all);

src/NuGet.Core/NuGet.Commands/RestoreCommand/RequestFactory/DependencyGraphSpecRequestProvider.cs

@@ -151,9 +151,10 @@ private RestoreSummaryRequest Create(
             {
                 // Set properties from the restore metadata
                 ProjectStyle = project.PackageSpec.RestoreMetadata.ProjectStyle,
+                //  Project.json is special cased to put assets file and generated .props and targets in the project folder
                 RestoreOutputPath = project.PackageSpec.RestoreMetadata.ProjectStyle == ProjectStyle.ProjectJson ? rootPath : project.PackageSpec.RestoreMetadata.OutputPath,
+                AssetsCachePath = projectPackageSpec.RestoreMetadata.OutputPath,
                 DependencyGraphSpec = projectDgSpec,
-                BaseIntermediateOutputPath = projectPackageSpec.RestoreMetadata.OutputPath,
                 ParentId = restoreArgs.ParentId
             };
 

src/NuGet.Core/NuGet.Commands/RestoreCommand/RestoreRequest.cs

@@ -132,16 +132,15 @@ public RestoreRequest(
         public ProjectStyle ProjectStyle { get; set; } = ProjectStyle.Unknown;
 
         /// <summary>
-        /// Restore output path
+        /// RestoreOutputPath, which is where the restore output (assets file and generated props and targets) will go
         /// </summary>
         public string RestoreOutputPath { get; set; }
 
         /// <summary>
-        /// Base Intermediate output path
+        /// AssetsCachePath, which is where the no-op restore cache will go
         /// </summary>
-        public string BaseIntermediateOutputPath { get; set; }
+        public string AssetsCachePath { get; set; }
 
-
         /// <summary>
         /// Compatibility options
         /// </summary>

src/NuGet.Core/NuGet.Commands/RestoreCommand/Utility/NoOpRestoreUtilities.cs

@@ -26,7 +26,7 @@ internal static bool IsNoOpSupported(RestoreRequest request)
         }
 
         /// <summary>
-        /// The cache file path is $(BaseIntermediateOutputPath)\$(project).nuget.cache
+        /// The cache file path is $(project).nuget.cache in the AssetsCachePath folder
         /// </summary>
         private static string GetBuildIntegratedProjectCacheFilePath(RestoreRequest request)
         {
@@ -35,7 +35,7 @@ private static string GetBuildIntegratedProjectCacheFilePath(RestoreRequest requ
                 || request.ProjectStyle == ProjectStyle.PackageReference
                 || request.ProjectStyle == ProjectStyle.Standalone)
             {
-                var cacheRoot = request.BaseIntermediateOutputPath ?? request.RestoreOutputPath;
+                var cacheRoot = request.AssetsCachePath;
                 return request.Project.RestoreMetadata.CacheFilePath = GetProjectCacheFilePath(cacheRoot, request.Project.RestoreMetadata.ProjectPath);
             }
 

src/NuGet.Core/NuGet.Common/Errors/NuGetLogCode.cs

@@ -4,7 +4,7 @@
 namespace NuGet.Common
 {
     /// <summary>
-    /// This enum is used to quantify NuGet error and wanring codes. 
+    /// This enum is used to quantify NuGet error and warning codes. 
     /// Format - NUxyzw where NU is the profix indicating NuGet and xyzw is a 4 digit code
     ///
     /// Numbers - xyzw

src/NuGet.Core/NuGet.Common/MsBuildStringUtility.cs

@@ -34,7 +34,7 @@ public static string[] Split(string s, params char[] chars)
                     .ToArray();
             }
 
-            return new string[0];
+            return Array.Empty<string>();
         }
 
         /// <summary>
@@ -59,7 +59,7 @@ public static string[] TrimAndExcludeNullOrEmpty(string[] strings)
         {
             if (strings == null)
             {
-                return new string[0];
+                return Array.Empty<string>();
             }
 
             return strings

src/NuGet.Core/NuGet.PackageManagement/Projects/ProjectBuildProperties.cs

@@ -9,7 +9,7 @@ namespace NuGet.ProjectManagement
     /// </summary>
     public static class ProjectBuildProperties
     {
-        public const string BaseIntermediateOutputPath = "BaseIntermediateOutputPath";
+        public const string MSBuildProjectExtensionsPath = "MSBuildProjectExtensionsPath";
         public const string PackageTargetFallback = "PackageTargetFallback";
         public const string AssetTargetFallback = "AssetTargetFallback";
         public const string PackageVersion = "PackageVersion";