From 8455a2307b5e9da495de6c726d29564a12df6b07 Mon Sep 17 00:00:00 2001
From: David Zidar <david@zidar.se>
Date: Tue, 25 Jan 2022 00:43:29 +0100
Subject: [PATCH] Fix concurrency issue in CSharpDiagnosticWorker

List<T> is not thread safe, use ImmutableList and ImmutableInterlocked
like CSharpDiagnosticWorkerWithAnalyzers does.
---
 .../Workers/Diagnostics/CSharpDiagnosticWorker.cs            | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/OmniSharp.Roslyn.CSharp/Workers/Diagnostics/CSharpDiagnosticWorker.cs b/src/OmniSharp.Roslyn.CSharp/Workers/Diagnostics/CSharpDiagnosticWorker.cs
index 56f6e9fa88..494072c396 100644
--- a/src/OmniSharp.Roslyn.CSharp/Workers/Diagnostics/CSharpDiagnosticWorker.cs
+++ b/src/OmniSharp.Roslyn.CSharp/Workers/Diagnostics/CSharpDiagnosticWorker.cs
@@ -141,7 +141,7 @@ public async Task<ImmutableArray<DocumentDiagnostics>> GetDiagnostics(ImmutableA
         {
             if (!documentPaths.Any()) return ImmutableArray<DocumentDiagnostics>.Empty;
 
-            var results = new List<DocumentDiagnostics>();
+            var results = ImmutableList<DocumentDiagnostics>.Empty;
 
             var documents =
                 (await Task.WhenAll(
@@ -164,7 +164,8 @@ public async Task<ImmutableArray<DocumentDiagnostics>> GetDiagnostics(ImmutableA
                             try
                             {
                                 var diagnostics = await GetDiagnosticsForDocument(document, projectName);
-                                results.Add(new DocumentDiagnostics(document.Id, document.FilePath, document.Project.Id, document.Project.Name, diagnostics));
+                                var documentDiagnostics = new DocumentDiagnostics(document.Id, document.FilePath, document.Project.Id, document.Project.Name, diagnostics);
+                                ImmutableInterlocked.Update(ref results, currentResults => currentResults.Add(documentDiagnostics));
                             }
                             finally
                             {