Support for ContentFiles in generated props.

Added support for writing out contentFiles to the generated props file.
Renamed buildCrossTargeting to buildMultiTargeting
Combined RestoreResult and MSBuildRestoreResult
MSBuild targets/props are now full members of nuget restore.

Fixes NuGet/Home#4098
Fixes NuGet/Home#3928
Fixes NuGet/Home#3683
Fixes NuGet/Home#3399
Fixes NuGet/Home#4116

src/NuGet.Core/NuGet.Client/ManagedCodeConventions.cs

@@ -24,15 +24,20 @@ public class ManagedCodeConventions
             PropertyNames.AnyValue,
             parser: (o, t) => o); // Identity parser, all strings are valid for any
         private static readonly ContentPropertyDefinition AssemblyProperty = new ContentPropertyDefinition(PropertyNames.ManagedAssembly,
-            parser: (o, t) => o.Equals(PackagingCoreConstants.EmptyFolder, StringComparison.Ordinal) ? o : null, // Accept "_._" as a pseudo-assembly
+            parser: AllowEmptyFolderParser,
             fileExtensions: new[] { ".dll", ".winmd", ".exe" });
-        private static readonly ContentPropertyDefinition MSBuildProperty = new ContentPropertyDefinition(PropertyNames.MSBuild, fileExtensions: new[] { ".targets", ".props" });
-        private static readonly ContentPropertyDefinition SatelliteAssemblyProperty = new ContentPropertyDefinition(PropertyNames.SatelliteAssembly, fileExtensions: new[] { ".resources.dll" });
+        private static readonly ContentPropertyDefinition MSBuildProperty = new ContentPropertyDefinition(PropertyNames.MSBuild,
+            parser: AllowEmptyFolderParser,
+            fileExtensions: new[] { ".targets", ".props" });
+        private static readonly ContentPropertyDefinition SatelliteAssemblyProperty = new ContentPropertyDefinition(PropertyNames.SatelliteAssembly,
+            parser: AllowEmptyFolderParser,
+            fileExtensions: new[] { ".resources.dll" });
 
         private static readonly ContentPropertyDefinition CodeLanguageProperty = new ContentPropertyDefinition(
             PropertyNames.CodeLanguage,
             parser: CodeLanguage_Parser);
 
+
         private static readonly Dictionary<string, object> DefaultTfmAny = new Dictionary<string, object>
         {
             { PropertyNames.TargetFrameworkMoniker, AnyFramework.Instance }
@@ -197,6 +202,12 @@ private static NuGetFramework TargetFrameworkName_ParserCore(string name)
             return new NuGetFramework(name, FrameworkConstants.EmptyVersion);
         }
 
+        private static object AllowEmptyFolderParser(string s, PatternTable table)
+        {
+            // Accept "_._" as a pseudo-assembly
+            return PackagingCoreConstants.EmptyFolder.Equals(s, StringComparison.Ordinal) ? s : null;
+        }
+
         private static bool TargetFrameworkName_CompatibilityTest(object criteria, object available)
         {
             var criteriaFrameworkName = criteria as NuGetFramework;
@@ -355,7 +366,7 @@ public class ManagedCodePatterns
             /// <summary>
             /// Pattern used to identify MSBuild global targets and props files
             /// </summary>
-            public PatternSet MSBuildCrossTargetingFiles { get; }
+            public PatternSet MSBuildMultiTargetingFiles { get; }
 
             /// <summary>
             /// Pattern used to identify content files
@@ -449,14 +460,20 @@ internal ManagedCodePatterns(ManagedCodeConventions conventions)
                         new PatternDefinition("build/{msbuild}", table: null, defaults: DefaultTfmAny)
                     });
 
-                MSBuildCrossTargetingFiles = new PatternSet(
+                MSBuildMultiTargetingFiles = new PatternSet(
                     conventions.Properties,
                     groupPatterns: new PatternDefinition[]
                     {
+                        new PatternDefinition("buildMultiTargeting/{msbuild?}", table: null, defaults: DefaultTfmAny),
+
+                        // deprecated
                         new PatternDefinition("buildCrossTargeting/{msbuild?}", table: null, defaults: DefaultTfmAny)
                     },
                     pathPatterns: new PatternDefinition[]
                     {
+                        new PatternDefinition("buildMultiTargeting/{msbuild}", table: null, defaults: DefaultTfmAny),
+
+                        // deprecated
                         new PatternDefinition("buildCrossTargeting/{msbuild}", table: null, defaults: DefaultTfmAny)
                     });
 

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

@@ -290,6 +290,8 @@ private bool IsCompatible(CompatibilityData compatibilityData)
                 compatibilityData.TargetLibrary.FrameworkAssemblies.Count > 0 ||                        // Framework Assemblies, or
                 compatibilityData.TargetLibrary.ContentFiles.Count > 0 ||                               // Shared content
                 compatibilityData.TargetLibrary.ResourceAssemblies.Count > 0 ||                         // Resources (satellite package)
+                compatibilityData.TargetLibrary.Build.Count > 0 ||                                      // Build
+                compatibilityData.TargetLibrary.BuildMultiTargeting.Count > 0 ||                        // Cross targeting build
                 !compatibilityData.Files.Any(p =>
                     p.StartsWith("ref/", StringComparison.OrdinalIgnoreCase)
                     || p.StartsWith("lib/", StringComparison.OrdinalIgnoreCase));                       // No assemblies at all (for any TxM)

src/NuGet.Core/NuGet.Commands/RestoreCommand/IRestoreResult.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.Collections.Generic;
 using NuGet.ProjectModel;
 
 namespace NuGet.Commands
@@ -24,5 +25,10 @@ public interface IRestoreResult
         /// The existing lock file. This is null if no lock file was provided on the <see cref="RestoreRequest"/>.
         /// </summary>
         LockFile PreviousLockFile { get; }
+
+        /// <summary>
+        /// Props and targets files to be written to disk.
+        /// </summary>
+        IEnumerable<MSBuildOutputFile> MSBuildOutputFiles { get; }
     }
 }

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

@@ -0,0 +1,33 @@
+// 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.Xml.Linq;
+
+namespace NuGet.Commands
+{
+    public class MSBuildOutputFile
+    {
+        /// <summary>
+        /// Output path on disk.
+        /// </summary>
+        public string Path { get; }
+
+        /// <summary>
+        /// MSBuild file content. This will be null for files
+        /// that should be removed.
+        /// </summary>
+        public XDocument Content { get; }
+
+        public MSBuildOutputFile (string path, XDocument content)
+        {
+            if (path == null)
+            {
+                throw new ArgumentNullException(nameof(path));
+            }
+
+            Path = path;
+            Content = content;
+        }
+    }
+}

src/NuGet.Core/NuGet.Commands/RestoreCommand/MSBuildRestoreImportGroup.cs → src/NuGet.Core/NuGet.Commands/RestoreCommand/MSBuildRestoreItemGroup.cs

@@ -1,14 +1,17 @@
 // 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.Collections.Generic;
 using System.Linq;
+using System.Xml.Linq;
 
 namespace NuGet.Commands
 {
-    public class MSBuildRestoreImportGroup
+    public class MSBuildRestoreItemGroup
     {
+        public static readonly string ItemGroup = nameof(ItemGroup);
+        public static readonly string ImportGroup = nameof(ImportGroup);
+
         /// <summary>
         /// Optional position arguement used when ordering groups in the output file.
         /// </summary>
@@ -20,9 +23,14 @@ public class MSBuildRestoreImportGroup
         public List<string> Conditions { get; set; } = new List<string>();
 
         /// <summary>
-        /// Project paths to import.
+        /// Items or imports.
         /// </summary>
-        public List<string> Imports { get; set; } = new List<string>();
+        public List<XElement> Items { get; set; } = new List<XElement>();
+
+        /// <summary>
+        /// Root element name.
+        /// </summary>
+        public string RootName { get; set; } = ImportGroup;
 
         /// <summary>
         /// Combined conditions
@@ -41,5 +49,21 @@ public string Condition
                 }
             }
         }
+
+        public static MSBuildRestoreItemGroup Create(
+            string rootName,
+            IEnumerable<XElement> items,
+            int position,
+            IEnumerable<string> conditions)
+        {
+            var group = new MSBuildRestoreItemGroup();
+
+            group.RootName = rootName;
+            group.Items.AddRange(items);
+            group.Position = position;
+            group.Conditions.AddRange(conditions);
+
+            return group;
+        }
     }
 }