C#: Address review comments and some light re-factoring.

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

@@ -59,14 +59,14 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
             this.progressMonitor.FindingFiles(srcDir);
 
             packageDirectory = new TemporaryDirectory(ComputeTempDirectory(sourceDir.FullName));
-            var allFiles = GetFiles("*.*").ToList();
-            var smallFiles = GetSmallFiles(allFiles);
-            this.fileContent = new FileContent(progressMonitor, GetFileNames(smallFiles));
-            this.allSources = GetFileNames(allFiles, ".cs").ToList();
-            var allProjects = GetFileNames(allFiles, ".csproj");
+            var allFiles = GetAllFiles().ToList();
+            var smallFiles = allFiles.SelectSmallFiles(progressMonitor).SelectFileNames();
+            this.fileContent = new FileContent(progressMonitor, smallFiles);
+            this.allSources = allFiles.SelectFileNamesByExtension(".cs").ToList();
+            var allProjects = allFiles.SelectFileNamesByExtension(".csproj");
             var solutions = options.SolutionFile is not null
                 ? new[] { options.SolutionFile }
-                : GetFileNames(allFiles, ".sln");
+                : allFiles.SelectFileNamesByExtension(".sln");
 
             var dllDirNames = options.DllDirs.Select(Path.GetFullPath).ToList();
 
@@ -156,7 +156,7 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
         {
             progressMonitor.LogInfo($"Generating source files from cshtml and razor files.");
 
-            var views = GetFileNames(allFiles, ".cshtml", ".razor").ToArray();
+            var views = allFiles.SelectFileNamesByExtension(".cshtml", ".razor").ToArray();
 
             if (views.Length > 0)
             {
@@ -184,31 +184,10 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
 
         public DependencyManager(string srcDir) : this(srcDir, DependencyOptions.Default, new ConsoleLogger(Verbosity.Info)) { }
 
-        private IEnumerable<FileInfo> GetFiles(string pattern, bool recurseSubdirectories = true) =>
-             sourceDir.GetFiles(pattern, new EnumerationOptions
-             {
-                 RecurseSubdirectories = recurseSubdirectories,
-                 MatchCasing = MatchCasing.CaseInsensitive
-             })
+        private IEnumerable<FileInfo> GetAllFiles() =>
+             sourceDir.GetFiles("*.*", new EnumerationOptions { RecurseSubdirectories = true })
                 .Where(d => d.Extension != ".dll" && !options.ExcludesFile(d.FullName));
 
-        private static IEnumerable<string> GetFileNames(IEnumerable<FileInfo> files, params string[] extensions) =>
-            files.Where(fi => !extensions.Any() || extensions.Contains(fi.Extension)).Select(fi => fi.FullName);
-
-        private IEnumerable<FileInfo> GetSmallFiles(IEnumerable<FileInfo> files)
-        {
-            const int oneMb = 1_048_576;
-            return files.Where(file =>
-            {
-                if (file.Length > oneMb)
-                {
-                    progressMonitor.LogDebug($"Skipping {file.FullName} because it is bigger than 1MB.");
-                    return false;
-                }
-                return true;
-            });
-        }
-
         /// <summary>
         /// Computes a unique temp directory for the packages associated
         /// with this source tree. Use a SHA1 of the directory name.
@@ -390,16 +369,14 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
 
         private void DownloadMissingPackages(List<FileInfo> allFiles)
         {
-            var nugetConfigs = allFiles
-                .Where(fi => fi.Name == "nuget.config")
-                .Select(fi => fi.FullName)
-                .ToArray();
+            var nugetConfigs = allFiles.SelectFileNamesByName("nuget.config").ToArray();
             string? nugetConfig = null;
             if (nugetConfigs.Length > 1)
             {
                 progressMonitor.MultipleNugetConfig(nugetConfigs);
-                nugetConfig = GetFiles("nuget.config", recurseSubdirectories: false)
-                    .Select(fi => fi.FullName)
+                nugetConfig = allFiles
+                    .SelectRootFiles(sourceDir)
+                    .SelectFileNamesByName("nuget.config")
                     .FirstOrDefault();
                 if (nugetConfig == null)
                 {
@@ -412,8 +389,7 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
             }
 
             var alreadyDownloadedPackages = Directory.GetDirectories(packageDirectory.DirInfo.FullName)
-                .Select(d => Path.GetFileName(d)
-                .ToLowerInvariant());
+                .Select(d => Path.GetFileName(d).ToLowerInvariant());
             var notYetDownloadedPackages = fileContent.AllPackages.Except(alreadyDownloadedPackages);
             foreach (var package in notYetDownloadedPackages)
             {

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

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+namespace Semmle.Extraction.CSharp.DependencyFetching
+{
+    public static class FileInfoExtensions
+    {
+        private static IEnumerable<string> SelectFilesAux(this IEnumerable<FileInfo> files, Predicate<FileInfo> p) =>
+            files.Where(f => p(f)).Select(fi => fi.FullName);
+
+        public static IEnumerable<FileInfo> SelectRootFiles(this IEnumerable<FileInfo> files, DirectoryInfo dir) =>
+            files.Where(file => file.DirectoryName == dir.FullName);
+
+        internal static IEnumerable<FileInfo> SelectSmallFiles(this IEnumerable<FileInfo> files, ProgressMonitor progressMonitor)
+        {
+            const int oneMb = 1_048_576;
+            return files.Where(file =>
+            {
+                if (file.Length > oneMb)
+                {
+                    progressMonitor.LogDebug($"Skipping {file.FullName} because it is bigger than 1MB.");
+                    return false;
+                }
+                return true;
+            });
+        }
+
+        public static IEnumerable<string> SelectFileNamesByExtension(this IEnumerable<FileInfo> files, params string[] extensions) =>
+            files.SelectFilesAux(fi => extensions.Contains(fi.Extension));
+
+        public static IEnumerable<string> SelectFileNamesByName(this IEnumerable<FileInfo> files, params string[] names) =>
+            files.SelectFilesAux(fi => names.Any(name => string.Compare(name, fi.Name, true) == 0));
+
+        public static IEnumerable<string> SelectFileNames(this IEnumerable<FileInfo> files) =>
+            files.SelectFilesAux(_ => true);
+    }
+}