Addressed feedback and some improvements for better readability

src/NuGet.Clients/NuGet.SolutionRestoreManager/SolutionRestoreJob.cs

@@ -315,15 +315,17 @@ private async Task RestoreAsync(bool forceRestore, RestoreOperationSource restor
                             var providerCache = new RestoreCommandProvidersCache();
                             Action<SourceCacheContext> cacheModifier = (cache) => { };
 
+                            var isRestoreOriginalAction = true;
                             var restoreSummaries = await DependencyGraphRestoreUtility.RestoreAsync(
                                 _solutionManager,
+                                dgSpec,
                                 cacheContext,
                                 providerCache,
                                 cacheModifier,
                                 sources,
                                 _nuGetProjectContext.OperationId,
                                 forceRestore,
-                                dgSpec,
+                                isRestoreOriginalAction,
                                 l,
                                 t);
 

src/NuGet.Core/NuGet.Commands/PackagesLockFileBuilder.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 NuGet.Common;
 using NuGet.LibraryModel;
@@ -12,19 +13,9 @@ namespace NuGet.Commands
 {
     public class PackagesLockFileBuilder
     {
-        private readonly int _lockFileVersion;
-
-        public PackagesLockFileBuilder(int lockFileVersion)
-        {
-            _lockFileVersion = lockFileVersion;
-        }
-
         public PackagesLockFile CreateNuGetLockFile(LockFile assetsFile)
         {
-            var lockFile = new PackagesLockFile()
-            {
-                Version = _lockFileVersion
-            };
+            var lockFile = new PackagesLockFile();
 
             var libraryLookup = assetsFile.Libraries.Where(e => e.Type == LibraryType.Package)
                 .ToDictionary(e => new PackageIdentity(e.Name, e.Version));
@@ -63,16 +54,16 @@ public PackagesLockFile CreateNuGetLockFile(LockFile assetsFile)
                     };
 
                     var framework_dep = framework?.Dependencies.FirstOrDefault(
-                        dep => PathUtility.GetStringComparerBasedOnOS().Equals(dep.Name, library.Name));
+                        dep => StringComparer.OrdinalIgnoreCase.Equals(dep.Name, library.Name));
 
                     if (framework_dep != null)
                     {
-                        dependency.Type = PackageInstallationType.Direct;
+                        dependency.Type = PackageDependencyType.Direct;
                         dependency.RequestedVersion = framework_dep.LibraryRange.VersionRange;
                     }
                     else
                     {
-                        dependency.Type = PackageInstallationType.Transitive;
+                        dependency.Type = PackageDependencyType.Transitive;
                     }
 
                     nuGettarget.Dependencies.Add(dependency);
@@ -84,7 +75,7 @@ public PackagesLockFile CreateNuGetLockFile(LockFile assetsFile)
                     {
                         Id = projectReference.Name,
                         Dependencies = projectReference.Dependencies,
-                        Type = PackageInstallationType.Project
+                        Type = PackageDependencyType.Project
                     };
 
                     nuGettarget.Dependencies.Add(dependency);

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

@@ -62,7 +62,7 @@ public class RestoreArgs
 
         public Guid ParentId { get; set; }
 
-        public bool IsRestore { get; set; } = true;
+        public bool IsRestoreOriginalAction { get; set; } = true;
 
         // Cache directory -> ISettings
         private ConcurrentDictionary<string, ISettings> _settingsCache
@@ -230,7 +230,7 @@ public void ApplyStandardProperties(RestoreRequest request)
             request.AllowNoOp = !request.CacheContext.NoCache && AllowNoOp;
             request.HideWarningsAndErrors = HideWarningsAndErrors;
             request.ParentId = ParentId;
-            request.IsRestore = IsRestore;
+            request.IsRestoreOriginalAction = IsRestoreOriginalAction;
         }
     }
 }

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

@@ -164,6 +164,6 @@ public class RestoreRequest
 
         public Guid ParentId { get; set;}
 
-        public bool IsRestore { get; set; } = true;
+        public bool IsRestoreOriginalAction { get; set; } = true;
     }
 }

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

@@ -196,7 +196,7 @@ public static bool VerifyPackagesOnDisk(RestoreRequest request)
         /// This methods handles the deduping of tools
         /// Handles the ignoring of RestoreSettings
         /// </summary>
-        public static DependencyGraphSpec GetDGSpec(RestoreRequest request)
+        public static string GetHash(RestoreRequest request)
         {
             if (request.Project.RestoreMetadata.ProjectStyle == ProjectStyle.DotnetCliTool || request.Project.RestoreMetadata.ProjectStyle == ProjectStyle.PackageReference)
             {
@@ -222,11 +222,11 @@ public static DependencyGraphSpec GetDGSpec(RestoreRequest request)
                 }
 
                 PersistHashedDGFileIfDebugging(dgSpec, request.Log);
-                return dgSpec;
+                return dgSpec.GetHash();
             }
 
             PersistHashedDGFileIfDebugging(request.DependencyGraphSpec, request.Log);
-            return request.DependencyGraphSpec;
+            return request.DependencyGraphSpec.GetHash();
         }
 
 

src/NuGet.Core/NuGet.DependencyResolver.Core/ResolverUtility.cs

@@ -204,7 +204,7 @@ public static GraphItem<RemoteResolveResult> CreateUnresolvedMatch(LibraryRange
             // This is only applicable when packages has to be resolved from packages.lock.json file
             if (lockFileLibraries.TryGetValue(key, out var libraries))
             {
-                var library = libraries.FirstOrDefault(lib => PathUtility.GetStringComparerBasedOnOS().Equals(lib.Name, libraryRange.Name));
+                var library = libraries.FirstOrDefault(lib => StringComparer.OrdinalIgnoreCase.Equals(lib.Name, libraryRange.Name));
 
                 if (library != null)
                 {

src/NuGet.Core/NuGet.PackageManagement/BuildIntegration/DependencyGraphRestoreUtility.cs

@@ -30,13 +30,14 @@ public static class DependencyGraphRestoreUtility
         /// </summary>
         public static async Task<IReadOnlyList<RestoreSummary>> RestoreAsync(
             ISolutionManager solutionManager,
+            DependencyGraphSpec dgSpec,
             DependencyGraphCacheContext context,
             RestoreCommandProvidersCache providerCache,
             Action<SourceCacheContext> cacheContextModifier,
             IEnumerable<SourceRepository> sources,
             Guid parentId,
             bool forceRestore,
-            DependencyGraphSpec dgSpec,
+            bool isRestoreOriginalAction,
             ILogger log,
             CancellationToken token)
         {
@@ -56,7 +57,7 @@ public static class DependencyGraphRestoreUtility
                         dgSpec,
                         parentId,
                         forceRestore,
-                        isRestore: true);
+                        isRestoreOriginalAction);
 
                     var restoreSummaries = await RestoreRunner.RunAsync(restoreContext, token);
 
@@ -71,49 +72,6 @@ public static class DependencyGraphRestoreUtility
             return new List<RestoreSummary>();
         }
 
-        /// <summary>
-        /// Restore a dg spec. This will not update the context cache.
-        /// </summary>
-        public static async Task<IReadOnlyList<RestoreSummary>> RestoreAsync(
-            DependencyGraphSpec dgSpec,
-            DependencyGraphCacheContext context,
-            RestoreCommandProvidersCache providerCache,
-            Action<SourceCacheContext> cacheContextModifier,
-            IEnumerable<SourceRepository> sources,
-            Guid parentId,
-            bool forceRestore,
-            ILogger log,
-            CancellationToken token)
-        {
-            // Check if there are actual projects to restore before running.
-            if (dgSpec.Restore.Count > 0)
-            {
-                using (var sourceCacheContext = new SourceCacheContext())
-                {
-                    // Update cache context
-                    cacheContextModifier(sourceCacheContext);
-
-                    var restoreContext = GetRestoreContext(
-                        context,
-                        providerCache,
-                        sourceCacheContext,
-                        sources,
-                        dgSpec,
-                        parentId,
-                        forceRestore: forceRestore,
-                        isRestore: false);
-
-                    var restoreSummaries = await RestoreRunner.RunAsync(restoreContext, token);
-
-                    RestoreSummary.Log(log, restoreSummaries);
-
-                    return restoreSummaries;
-                }
-            }
-
-            return new List<RestoreSummary>();
-        }
-
         private static async Task PersistDGSpec(DependencyGraphSpec dgSpec)
         {
             try
@@ -176,7 +134,7 @@ private static async Task PersistDGSpec(DependencyGraphSpec dgSpec)
                     dgFile,
                     parentId,
                     forceRestore: true,
-                    isRestore: false);
+                    isRestoreOriginalAction: false);
 
                 var requests = await RestoreRunner.GetRequests(restoreContext);
                 var results = await RestoreRunner.RunWithoutCommit(requests, restoreContext);
@@ -289,7 +247,7 @@ public static async Task<PackageSpec> GetProjectSpec(IDependencyGraphProject pro
             DependencyGraphSpec dgFile,
             Guid parentId,
             bool forceRestore,
-            bool isRestore)
+            bool isRestoreOriginalAction)
         {
             var caching = new CachingSourceProvider(new PackageSourceProvider(context.Settings));
             foreach( var source in sources)
@@ -307,7 +265,7 @@ public static async Task<PackageSpec> GetProjectSpec(IDependencyGraphProject pro
                 AllowNoOp = !forceRestore,
                 CachingSourceProvider = caching,
                 ParentId = parentId,
-                IsRestore = isRestore
+                IsRestoreOriginalAction = isRestoreOriginalAction
             };
 
             return restoreContext;

src/NuGet.Core/NuGet.PackageManagement/NuGetPackageManager.cs

@@ -2892,15 +2892,17 @@ var projectUniqueNamesForBuildIntToUpdate
                     // Restore and commit the lock file to disk regardless of the result
                     // This will restore all parents in a single restore 
                     await DependencyGraphRestoreUtility.RestoreAsync(
+                        SolutionManager,
                         dgSpecForParents,
                         referenceContext,
                         GetRestoreProviderCache(),
                         cacheContextModifier,
                         projectAction.Sources,
                         nuGetProjectContext.OperationId,
-                        false, // No need to force restore as the inputs would've changed here anyways
-                        logger,
-                        token);
+                        forceRestore: false, // No need to force restore as the inputs would've changed here anyways
+                        isRestoreOriginalAction: false, // not an explicit restore request instead being done as part of install or update
+                        log: logger,
+                        token: token);
                 }
             }
             else

src/NuGet.Core/NuGet.ProjectModel/JsonUtility.cs

@@ -1,14 +1,20 @@
 // 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.IO;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using NuGet.Packaging.Core;
+using NuGet.Versioning;
 
 namespace NuGet.ProjectModel
 {
     internal static class JsonUtility
     {
+        internal static readonly char[] PathSplitChars = new[] { LockFile.DirectorySeparatorChar };
+
         /// <summary>
         /// JsonLoadSettings with line info and comments ignored.
         /// </summary>
@@ -36,5 +42,73 @@ internal static JObject LoadJson(TextReader reader)
                 return JObject.Load(jsonReader, DefaultLoadSettings);
             }
         }
+
+        internal static PackageDependency ReadPackageDependency(string property, JToken json)
+        {
+            var versionStr = json.Value<string>();
+            return new PackageDependency(
+                property,
+                versionStr == null ? null : VersionRange.Parse(versionStr));
+        }
+
+        internal static JProperty WritePackageDependency(PackageDependency item)
+        {
+            return new JProperty(
+                item.Id,
+                WriteString(item.VersionRange?.ToLegacyShortString()));
+        }
+
+        internal static TItem ReadProperty<TItem>(JObject jObject, string propertyName)
+        {
+            if (jObject != null)
+            {
+                JToken value;
+                if (jObject.TryGetValue(propertyName, out value) && value != null)
+                {
+                    return value.Value<TItem>();
+                }
+            }
+
+            return default(TItem);
+        }
+
+        internal static IList<TItem> ReadObject<TItem>(JObject jObject, Func<string, JToken, TItem> readItem)
+        {
+            if (jObject == null)
+            {
+                return new List<TItem>();
+            }
+            var items = new List<TItem>();
+            foreach (var child in jObject)
+            {
+                items.Add(readItem(child.Key, child.Value));
+            }
+            return items;
+        }
+
+        internal static JObject WriteObject<TItem>(IEnumerable<TItem> items, Func<TItem, JProperty> writeItem)
+        {
+            var array = new JObject();
+            foreach (var item in items)
+            {
+                array.Add(writeItem(item));
+            }
+            return array;
+        }
+
+        internal static int ReadInt(JToken cursor, string property, int defaultValue)
+        {
+            var valueToken = cursor[property];
+            if (valueToken == null)
+            {
+                return defaultValue;
+            }
+            return valueToken.Value<int>();
+        }
+
+        internal static JToken WriteString(string item)
+        {
+            return item != null ? new JValue(item) : JValue.CreateNull();
+        }
     }
 }

src/NuGet.Core/NuGet.ProjectModel/LockFile/LockFile.cs

@@ -132,21 +132,6 @@ public bool Equals(LockFile other)
                 && LogsEqual(other.LogMessages);
         }
 
-        public LockFile Clone()
-        {
-            var lockFile = new LockFile();
-            lockFile.Version = Version;
-            lockFile.Path = Path;
-            lockFile.ProjectFileDependencyGroups = ProjectFileDependencyGroups?.Select(item => item.Clone()).ToList();
-            lockFile.Libraries = Libraries?.Select(item => item.Clone()).ToList();
-            lockFile.Targets = Targets?.Select(item => item.Clone()).ToList();
-            lockFile.PackageFolders = new List<LockFileItem>(PackageFolders);
-            lockFile.PackageSpec = PackageSpec.Clone();
-            lockFile.LogMessages = new List<IAssetsLogMessage>(LogMessages);
-
-            return lockFile;
-        }
-
         private bool LogsEqual(IList<IAssetsLogMessage> otherLogMessages)
         {
             if (ReferenceEquals(LogMessages, otherLogMessages))