C#: Address review comments.

Author: michaelnebel

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

@@ -57,6 +57,6 @@ public void Dispose()
             }
         }
 
-        public override string ToString() => DirInfo.FullName.ToString();
+        public override string ToString() => DirInfo.FullName;
     }
 }

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

@@ -24,8 +24,8 @@ internal class NugetExeWrapper : IDisposable
         private readonly FileProvider fileProvider;
 
         /// <summary>
-        /// The computed packages directory.
-        /// This will be in the Cached or Temp location
+        /// The packages directory.
+        /// This will be in the user-specified or computed Temp location
         /// so as to not trample the source tree.
         /// </summary>
         private readonly DependencyDirectory packageDirectory;

csharp/extractor/Semmle.Util/EnvironmentVariables.cs

@@ -79,9 +79,8 @@ public static IEnumerable<string> GetURLs(string name)
 
         /// <summary>
         /// If set, returns the directory where buildless dependencies should be stored.
-        /// This is needed for caching dependencies.
+        /// This can be used for caching dependencies.
         /// </summary>
-        /// <returns></returns>
         public static string? GetBuildlessDependencyDir()
         {
             return Environment.GetEnvironmentVariable("CODEQL_EXTRACTOR_CSHARP_OPTION_BUILDLESS_DEPENDENCY_DIR");

csharp/ql/integration-tests/all-platforms/standalone_dependency_dir/test.py

@@ -6,3 +6,7 @@ def test(codeql, csharp, cwd):
     # The Assemblies.ql query shows that the Newtonsoft assembly is found in the
     # dependency directory set above.
     codeql.database.create(source_root="proj", build_mode="none")
+
+    # Check that the packages directory has been created in the dependecies folder.
+    packages_dir = os.path.join(path, "packages")
+    assert os.path.isdir(packages_dir), "The packages directory was not created in the specified dependency directory."