C#: Add aggregated compiler and extractor message counts to extraction telemetry query

csharp/extractor/Semmle.Extraction/BUILD.bazel

@@ -26,6 +26,7 @@ codeql_csharp_library(
         ],
         "//conditions:default": [],
     }),
+    internals_visible_to = ["Semmle.Extraction.CSharp"],
     visibility = ["//csharp:__subpackages__"],
     deps = [
         "//csharp/extractor/Semmle.Util",

csharp/extractor/Semmle.Extraction/Entities/ExtractionMessage.cs

@@ -1,4 +1,5 @@
-using System.IO;
+using System.Collections.Concurrent;
+using System.IO;
 using System.Threading;
 using Semmle.Util;
 
@@ -7,6 +8,8 @@ namespace Semmle.Extraction.Entities
     internal class ExtractionMessage : FreshEntity
     {
         private static readonly int limit = EnvironmentVariables.TryGetExtractorNumberOption<int>("MESSAGE_LIMIT") ?? 10000;
+
+        internal static readonly ConcurrentDictionary<string, int> groupedMessageCounts = [];
         private static int messageCount = 0;
 
         private readonly Message msg;
@@ -25,6 +28,10 @@ namespace Semmle.Extraction.Entities
 
         protected override void Populate(TextWriter trapFile)
         {
+            // For the time being we're counting the number of messages per severity, we could introduce other groupings in the future
+            var key = msg.Severity.ToString();
+            groupedMessageCounts.AddOrUpdate(key, 1, (_, c) => c + 1);
+
             if (!bypassLimit)
             {
                 var val = Interlocked.Increment(ref messageCount);

csharp/extractor/Semmle.Extraction/Semmle.Extraction.csproj

@@ -5,6 +5,8 @@
 	</PropertyGroup>
 	<ItemGroup>
 		<ProjectReference Include="..\Semmle.Util\Semmle.Util.csproj" />
+
+		<InternalsVisibleTo Include="Semmle.Extraction.CSharp" />
 	</ItemGroup>
   <Import Project="..\..\.paket\Paket.Restore.targets" />
 </Project>