C#: Fix working directory structures in standalone

Author: tamasvajk

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

@@ -52,7 +52,7 @@ public DependencyManager(string srcDir, IDependencyOptions options, ILogger logg
             this.progressMonitor = new ProgressMonitor(logger);
             this.sourceDir = new DirectoryInfo(srcDir);
 
-            packageDirectory = new TemporaryDirectory(ComputeTempDirectory(sourceDir.FullName));
+            packageDirectory = new TemporaryDirectory(ComputeTempDirectory(sourceDir.FullName, "packages"));
             legacyPackageDirectory = new TemporaryDirectory(ComputeTempDirectory(sourceDir.FullName, "legacypackages"));
             missingPackageDirectory = new TemporaryDirectory(ComputeTempDirectory(sourceDir.FullName, "missingpackages"));
 
@@ -467,15 +467,15 @@ private IEnumerable<FileInfo> GetAllFiles()
         /// with this source tree. Use a SHA1 of the directory name.
         /// </summary>
         /// <returns>The full path of the temp directory.</returns>
-        private static string ComputeTempDirectory(string srcDir, string packages = "packages")
+        private static string ComputeTempDirectory(string srcDir, string subfolderName)
         {
             var bytes = Encoding.Unicode.GetBytes(srcDir);
             var sha = SHA1.HashData(bytes);
             var sb = new StringBuilder();
             foreach (var b in sha.Take(8))
                 sb.AppendFormat("{0:x2}", b);
 
-            return Path.Combine(FileUtils.GetTemporaryWorkingDirectory(out var _), "GitHub", packages, sb.ToString());
+            return Path.Combine(FileUtils.GetTemporaryWorkingDirectory(out var _), sb.ToString(), subfolderName);
         }
 
         /// <summary>
@@ -723,7 +723,7 @@ private void DownloadMissingPackages(List<FileInfo> allFiles, ISet<string> dllPa
             Parallel.ForEach(notYetDownloadedPackages, new ParallelOptions { MaxDegreeOfParallelism = options.Threads }, package =>
             {
                 progressMonitor.NugetInstall(package);
-                using var tempDir = new TemporaryDirectory(ComputeTempDirectory(package));
+                using var tempDir = new TemporaryDirectory(ComputeTempDirectory(package, "missingpackages_workingdir"));
                 var success = dotnet.New(tempDir.DirInfo.FullName);
                 if (!success)
                 {

csharp/extractor/Semmle.Util/FileUtils.cs

@@ -144,20 +144,40 @@ public static string NestPaths(ILogger logger, string? outerpath, string innerpa
             return nested;
         }
 
+        private static string? tempFolderPath = null;
+        private static readonly object lockObject = new();
+
         public static string GetTemporaryWorkingDirectory(Func<string, string?> getEnvironmentVariable, string lang, out bool shouldCleanUp)
         {
             shouldCleanUp = false;
             var tempFolder = getEnvironmentVariable($"CODEQL_EXTRACTOR_{lang}_SCRATCH_DIR");
+            if (!string.IsNullOrEmpty(tempFolder))
+            {
+                return tempFolder;
+            }
 
-            if (string.IsNullOrEmpty(tempFolder))
+            if (!string.IsNullOrEmpty(tempFolderPath))
             {
+                shouldCleanUp = true;
+                return tempFolderPath;
+            }
+
+            lock (lockObject)
+            {
+                if (!string.IsNullOrEmpty(tempFolderPath))
+                {
+                    shouldCleanUp = true;
+                    return tempFolderPath;
+                }
+
                 var tempPath = Path.GetTempPath();
                 var name = Guid.NewGuid().ToString("N").ToUpper();
                 tempFolder = Path.Combine(tempPath, "GitHub", name);
+                Directory.CreateDirectory(tempFolder);
+                tempFolderPath = tempFolder;
                 shouldCleanUp = true;
+                return tempFolder;
             }
-
-            return tempFolder;
         }
 
         public static string GetTemporaryWorkingDirectory(out bool shouldCleanUp) =>