C#: Add support to the extractor for getting the compression extractor option.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Extractor/Options.cs

@@ -46,7 +46,9 @@ public static Options CreateWithEnvironment(string[] arguments)
             var argsList = new List<string>(arguments);
 
             if (!string.IsNullOrEmpty(extractionOptions))
+            {
                 argsList.AddRange(extractionOptions.Split(' '));
+            }
 
             options.ParseArguments(argsList);
             return options;

csharp/extractor/Semmle.Extraction/Options.cs

@@ -1,3 +1,4 @@
+using System;
 using Semmle.Util.Logging;
 using Semmle.Util;
 
@@ -49,6 +50,7 @@ public abstract class CommonOptions : ICommandLineOptions
         /// </summary>
         public bool QlTest { get; private set; } = false;
 
+
         /// <summary>
         /// The compression algorithm used for trap files.
         /// </summary>
@@ -64,6 +66,16 @@ public virtual bool HandleOption(string key, string value)
                 case "verbosity":
                     Verbosity = (Verbosity)int.Parse(value);
                     return true;
+                case "compression":
+                    try
+                    {
+                        TrapCompression = (TrapWriter.CompressionMode)Enum.Parse(typeof(TrapWriter.CompressionMode), value, true);
+                        return true;
+                    }
+                    catch (ArgumentException)
+                    {
+                        return false;
+                    }
                 default:
                     return false;
             }

csharp/extractor/Semmle.Util/CommandLineOptions.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 
 namespace Semmle.Util
@@ -39,8 +40,26 @@ public interface ICommandLineOptions
 
     public static class OptionsExtensions
     {
-        public static void ParseArguments(this ICommandLineOptions options, IReadOnlyList<string> arguments)
+        private static string? GetExtractorOption(string name) =>
+            Environment.GetEnvironmentVariable($"CODEQL_EXTRACTOR_CSHARP_OPTION_{name.ToUpper()}");
+
+        private static List<string> GetExtractorOptions()
+        {
+            var extractorOptions = new List<string>();
+
+            var compressionMode = GetExtractorOption("compression");
+            if (!string.IsNullOrEmpty(compressionMode))
+            {
+                extractorOptions.Add($"--compression:{compressionMode}");
+            }
+
+            return extractorOptions;
+        }
+
+        public static void ParseArguments(this ICommandLineOptions options, IReadOnlyList<string> providedArguments)
         {
+            var arguments = GetExtractorOptions();
+            arguments.AddRange(providedArguments);
             for (var i = 0; i < arguments.Count; ++i)
             {
                 var arg = arguments[i];