C#: Address review comments

Author: hvitved

csharp/autobuilder/Semmle.Autobuild.Tests/BuildScripts.cs

@@ -135,8 +135,6 @@ string IBuildActions.PathCombine(params string[] parts)
 
         string IBuildActions.GetFullPath(string path) => path;
 
-        string IBuildActions.GetDirectoryName(string path) => System.IO.Path.GetDirectoryName(path);
-
         void IBuildActions.WriteAllText(string filename, string contents)
         {
         }

csharp/autobuilder/Semmle.Autobuild/Autobuilder.cs

@@ -128,9 +128,10 @@ public Autobuilder(IBuildActions actions, AutobuildOptions options)
 
             projectsOrSolutionsToBuildLazy = new Lazy<IList<IProjectOrSolution>>(() =>
             {
+                List<IProjectOrSolution> ret;
                 if (options.Solution.Any())
                 {
-                    var ret = new List<IProjectOrSolution>();
+                    ret = new List<IProjectOrSolution>();
                     foreach (var solution in options.Solution)
                     {
                         if (actions.FileExists(solution))
@@ -141,53 +142,43 @@ public Autobuilder(IBuildActions actions, AutobuildOptions options)
                     return ret;
                 }
 
-                bool FindFiles(string extension, Func<string, ProjectOrSolution> create, out IEnumerable<IProjectOrSolution> files)
+                IEnumerable<IProjectOrSolution> FindFiles(string extension, Func<string, ProjectOrSolution> create)
                 {
-                    var allFiles = GetExtensions(extension).
+                    var matchingFiles = GetExtensions(extension).
                         Select(p => (ProjectOrSolution: create(p.Item1), DistanceFromRoot: p.Item2)).
                         Where(p => p.ProjectOrSolution.HasLanguage(this.Options.Language)).
                         ToArray();
 
-                    if (allFiles.Length == 0)
-                    {
-                        files = null;
-                        return false;
-                    }
+                    if (matchingFiles.Length == 0)
+                        return null;
 
                     if (options.AllSolutions)
-                    {
-                        files = allFiles.Select(p => p.ProjectOrSolution);
-                        return true;
-                    }
+                        return matchingFiles.Select(p => p.ProjectOrSolution);
 
-                    var firstIsClosest = allFiles.Length > 1 && allFiles[0].DistanceFromRoot < allFiles[1].DistanceFromRoot;
-                    if (allFiles.Length == 1 || firstIsClosest)
-                    {
-                        files = allFiles.Select(p => p.ProjectOrSolution).Take(1);
-                        return true;
-                    }
+                    var firstIsClosest = matchingFiles.Length > 1 && matchingFiles[0].DistanceFromRoot < matchingFiles[1].DistanceFromRoot;
+                    if (matchingFiles.Length == 1 || firstIsClosest)
+                        return matchingFiles.Select(p => p.ProjectOrSolution).Take(1);
 
-                    var candidates = allFiles.
-                        Where(f => f.DistanceFromRoot == allFiles[0].DistanceFromRoot).
+                    var candidates = matchingFiles.
+                        Where(f => f.DistanceFromRoot == matchingFiles[0].DistanceFromRoot).
                         Select(f => f.ProjectOrSolution);
                     Log(Severity.Info, $"Found multiple '{extension}' files, giving up: {string.Join(", ", candidates)}.");
-                    files = new IProjectOrSolution[0];
-                    return true;
+                    return new IProjectOrSolution[0];
                 }
 
                 // First look for `.proj` files
-                if (FindFiles(".proj", f => new Project(this, f), out var ret1))
-                    return ret1.ToList();
+                ret = FindFiles(".proj", f => new Project(this, f))?.ToList();
+                if (ret != null)
+                    return ret;
 
                 // Then look for `.sln` files
-                if (FindFiles(".sln", f => new Solution(this, f), out var ret2))
-                    return ret2.ToList();
+                ret = FindFiles(".sln", f => new Solution(this, f))?.ToList();
+                if (ret != null)
+                    return ret;
 
                 // Finally look for language specific project files, e.g. `.csproj` files
-                if (FindFiles(this.Options.Language.ProjectExtension, f => new Project(this, f), out var ret3))
-                    return ret3.ToList();
-
-                return new List<IProjectOrSolution>();
+                ret = FindFiles(this.Options.Language.ProjectExtension, f => new Project(this, f))?.ToList();
+                return ret ?? new List<IProjectOrSolution>();
             });
 
             SemmleDist = Actions.GetEnvironmentVariable("SEMMLE_DIST");

csharp/autobuilder/Semmle.Autobuild/BuildActions.cs

@@ -102,11 +102,6 @@ public interface IBuildActions
         /// </summary>
         string GetFullPath(string path);
 
-        /// <summary>
-        /// Gets the directory of <paramref name="path"/>, Path.GetDirectoryName().
-        /// </summary>
-        string GetDirectoryName(string path);
-
         /// <summary>
         /// Writes contents to file, File.WriteAllText().
         /// </summary>
@@ -192,8 +187,6 @@ XmlDocument IBuildActions.LoadXml(string filename)
 
         string IBuildActions.GetFullPath(string path) => Path.GetFullPath(path);
 
-        string IBuildActions.GetDirectoryName(string path) => Path.GetDirectoryName(path);
-
         public static readonly IBuildActions Instance = new SystemBuildActions();
     }
 }

csharp/autobuilder/Semmle.Autobuild/BuildCommandAutoRule.cs

@@ -40,7 +40,7 @@ public BuildScript Analyse(Autobuilder builder)
             chmod.RunCommand("/bin/chmod", $"u+x {scriptPath}");
             var chmodScript = builder.Actions.IsWindows() ? BuildScript.Success : BuildScript.Try(chmod.Script);
 
-            var dir = builder.Actions.GetDirectoryName(scriptPath);
+            var dir = Path.GetDirectoryName(scriptPath);
 
             // A specific .NET Core version may be required
             return chmodScript & DotNetRule.WithDotNet(builder, dotNet =>

csharp/autobuilder/Semmle.Autobuild/BuildScript.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.IO;
-using Semmle.Util;
 
 namespace Semmle.Autobuild
 {

csharp/autobuilder/Semmle.Autobuild/MsBuildRule.cs

@@ -1,5 +1,4 @@
 using Semmle.Util.Logging;
-using System.IO;
 using System.Linq;
 
 namespace Semmle.Autobuild

csharp/autobuilder/Semmle.Autobuild/Project.cs

@@ -78,7 +78,7 @@ public Project(Autobuilder builder, string path) : base(builder, path)
                 foreach (var include in projectFileIncludes.Concat(projectFilesIncludes))
                 {
                     var includePath = builder.Actions.IsWindows() ? include.Value : include.Value.Replace("\\", "/");
-                    includedProjects.Add(new Project(builder, builder.Actions.PathCombine(builder.Actions.GetDirectoryName(this.FullPath), includePath)));
+                    includedProjects.Add(new Project(builder, builder.Actions.PathCombine(Path.GetDirectoryName(this.FullPath), includePath)));
                 }
             }
         }

csharp/autobuilder/Semmle.Autobuild/ProjectOrSolution.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 
 namespace Semmle.Autobuild