C#: Code quality improvements.

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

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using Semmle.Util.Logging;
+
+namespace Semmle.Extraction.CSharp.DependencyFetching
+{
+    /// <summary>
+    /// Used to represent a path to an assembly or a directory containing assemblies
+    /// and a selector function to determine which files to include, when indexing the assemblies.
+    /// </summary>
+    internal sealed class AssemblyLookupLocation(string p, Func<string, bool> includeFileName)
+    {
+        public string Path => p;
+
+        public AssemblyLookupLocation(string p) : this(p, _ => true) { }
+
+        public static implicit operator AssemblyLookupLocation(string path) => new(path);
+
+        /// <summary>
+        /// Finds all assemblies nested within the directory `path`
+        /// and adds them to the a list of assembly names to index.
+        /// Indexing is performed at a later stage. This only collects the names.
+        /// </summary>
+        /// <param name="dir">The directory to index.</param>
+        private void AddReferenceDirectory(List<string> dllsToIndex, ILogger logger)
+        {
+            foreach (var dll in new DirectoryInfo(p).EnumerateFiles("*.dll", SearchOption.AllDirectories))
+            {
+                if (includeFileName(dll.Name))
+                {
+                    dllsToIndex.Add(dll.FullName);
+                }
+                else
+                {
+                    logger.LogInfo($"AssemblyLookupLocation: Skipping {dll.FullName}.");
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns a list of paths to all assemblies in `p` that should be indexed.
+        /// </summary>
+        /// <param name="logger">Logger</param>
+        public List<string> GetDlls(ILogger logger)
+        {
+            var dllsToIndex = new List<string>();
+            if (File.Exists(p))
+            {
+                if (includeFileName(System.IO.Path.GetFileName(p)))
+                {
+                    dllsToIndex.Add(p);
+                }
+                else
+                {
+                    logger.LogInfo($"AssemblyLookupLocation: Skipping {p}.");
+                }
+                return dllsToIndex;
+            }
+
+            if (Directory.Exists(p))
+            {
+                logger.LogInfo($"AssemblyLookupLocation: Finding reference DLLs in {p}...");
+                AddReferenceDirectory(dllsToIndex, logger);
+            }
+            else
+            {
+                logger.LogInfo("AssemblyLookupLocation: Path not found: " + p);
+            }
+            return dllsToIndex;
+        }
+
+        public override bool Equals(object? obj) =>
+            obj is AssemblyLookupLocation ap && p.Equals(ap.Path);
+
+        public override int GetHashCode() => p.GetHashCode();
+
+        public override string ToString() => p;
+    }
+}