Merge pull request #14016 from hvitved/csharp/codeql-threads

C#: Respect `$CODEQL_THREADS` environment variable

Author: hvitved

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyManager.cs

@@ -377,7 +377,7 @@ private void DownloadMissingPackages()
 
         private void AnalyseSolutions(IEnumerable<string> solutions)
         {
-            Parallel.ForEach(solutions, new ParallelOptions { MaxDegreeOfParallelism = 4 }, solutionFile =>
+            Parallel.ForEach(solutions, new ParallelOptions { MaxDegreeOfParallelism = options.Threads }, solutionFile =>
             {
                 try
                 {

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependencyOptions.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Linq;
 using System.Collections.Generic;
+using Semmle.Util;
 
 namespace Semmle.Extraction.CSharp.DependencyFetching
 {
@@ -49,6 +51,11 @@ public interface IDependencyOptions
         /// <param name="path">The path to query.</param>
         /// <returns>True iff the path matches an exclusion.</returns>
         bool ExcludesFile(string path);
+
+        /// <summary>
+        /// The number of threads to use.
+        /// </summary>
+        int Threads { get; }
     }
 
     public class DependencyOptions : IDependencyOptions
@@ -71,5 +78,7 @@ public class DependencyOptions : IDependencyOptions
 
         public bool ExcludesFile(string path) =>
             Excludes.Any(path.Contains);
+
+        public int Threads { get; set; } = EnvironmentVariables.GetDefaultNumberOfThreads();
     }
 }

csharp/extractor/Semmle.Extraction/Options.cs

@@ -13,7 +13,7 @@ public abstract class CommonOptions : ICommandLineOptions
         /// <summary>
         /// The specified number of threads, or the default if unspecified.
         /// </summary>
-        public int Threads { get; private set; } = System.Environment.ProcessorCount;
+        public int Threads { get; private set; } = EnvironmentVariables.GetDefaultNumberOfThreads();
 
         /// <summary>
         /// The verbosity used in output and logging.

csharp/extractor/Semmle.Util/CommandLineOptions.cs

@@ -41,16 +41,13 @@ public interface ICommandLineOptions
     public static class OptionsExtensions
     {
         private static readonly string[] ExtractorOptions = new[] { "trap_compression", "cil" };
-        private static string? GetExtractorOption(string name) =>
-            Environment.GetEnvironmentVariable($"CODEQL_EXTRACTOR_CSHARP_OPTION_{name.ToUpper()}");
-
         private static List<string> GetExtractorOptions()
         {
             var extractorOptions = new List<string>();
 
             foreach (var option in ExtractorOptions)
             {
-                var value = GetExtractorOption(option);
+                var value = EnvironmentVariables.GetExtractorOption(option);
                 if (!string.IsNullOrEmpty(value))
                 {
                     extractorOptions.Add($"--{option}:{value}");

csharp/extractor/Semmle.Util/EnvironmentVariables.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace Semmle.Util
+{
+    public class EnvironmentVariables
+    {
+        public static string? GetExtractorOption(string name) =>
+            Environment.GetEnvironmentVariable($"CODEQL_EXTRACTOR_CSHARP_OPTION_{name.ToUpper()}");
+
+        public static int GetDefaultNumberOfThreads()
+        {
+            if (!int.TryParse(Environment.GetEnvironmentVariable("CODEQL_THREADS"), out var threads) || threads == -1)
+            {
+                threads = Environment.ProcessorCount;
+            }
+            return threads;
+        }
+    }
+}