From efd0158d791247ce35f7089639e8eda8b6937231 Mon Sep 17 00:00:00 2001
From: Roman Konecny <rokonecn@microsoft.com>
Date: Fri, 27 Oct 2023 10:39:20 +0200
Subject: [PATCH] Cache Platform Negotiation in graph build (#9343)

* Cache Platform Negotiation in graph build
* Clean cached data after build.
---
 src/Build/Graph/GraphBuilder.cs | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/Build/Graph/GraphBuilder.cs b/src/Build/Graph/GraphBuilder.cs
index a92da0f73f9..58f9af58bdf 100644
--- a/src/Build/Graph/GraphBuilder.cs
+++ b/src/Build/Graph/GraphBuilder.cs
@@ -48,6 +48,7 @@ internal class GraphBuilder
 
         private readonly ProjectGraph.ProjectInstanceFactoryFunc _projectInstanceFactory;
         private IReadOnlyDictionary<string, IReadOnlyCollection<string>> _solutionDependencies;
+        private ConcurrentDictionary<ConfigurationMetadata, Lazy<ProjectInstance>> _platformNegotiationInstancesCache = new();
 
         public GraphBuilder(
             IEnumerable<ProjectGraphEntryPoint> entryPoints,
@@ -92,6 +93,9 @@ public void BuildGraph()
 
             RootNodes = GetGraphRoots(EntryPointNodes);
             ProjectNodes = allParsedProjects.Values.Select(p => p.GraphNode).ToList();
+
+            // Clean and release some temporary used large memory objects.
+            _platformNegotiationInstancesCache.Clear();
         }
 
         private static IReadOnlyCollection<ProjectGraphNode> GetGraphRoots(IReadOnlyCollection<ProjectGraphNode> entryPointNodes)
@@ -576,7 +580,7 @@ private List<ProjectInterpretation.ReferenceInfo> ParseReferences(ProjectGraphNo
         {
             var referenceInfos = new List<ProjectInterpretation.ReferenceInfo>();
 
-            foreach (var referenceInfo in _projectInterpretation.GetReferences(parsedProject.ProjectInstance, _projectCollection, _projectInstanceFactory))
+            foreach (var referenceInfo in _projectInterpretation.GetReferences(parsedProject.ProjectInstance, _projectCollection, GetInstanceForPlatformNegotiationWithCaching))
             {
                 if (FileUtilities.IsSolutionFilename(referenceInfo.ReferenceConfiguration.ProjectFullPath))
                 {
@@ -594,6 +598,16 @@ private List<ProjectInterpretation.ReferenceInfo> ParseReferences(ProjectGraphNo
             return referenceInfos;
         }
 
+        private ProjectInstance GetInstanceForPlatformNegotiationWithCaching(
+            string projectPath,
+            Dictionary<string, string> globalProperties,
+            ProjectCollection projectCollection)
+        {
+            return _platformNegotiationInstancesCache.GetOrAdd(
+                new ConfigurationMetadata(projectPath, CreatePropertyDictionary(globalProperties)), 
+                new Lazy<ProjectInstance>(() => _projectInstanceFactory(projectPath, globalProperties, projectCollection))).Value;
+        }
+
         internal static string FormatCircularDependencyError(List<string> projectsInCycle)
         {
             var errorMessage = new StringBuilder(projectsInCycle.Select(p => p.Length).Sum());