feat: speed up MockFileSystem constructor (#698)

Co-authored-by: Samuel Bernhard <sbernhard@hamilton.ch>

Author: schibu007

benchmarks/System.IO.Abstractions.Benchmarks/MockFileSystemBenchmarks.cs

@@ -0,0 +1,27 @@
+using BenchmarkDotNet.Attributes;
+using System.Collections.Generic;
+using System.IO.Abstractions.TestingHelpers;
+using System.Linq;
+using XFS = System.IO.Abstractions.TestingHelpers.MockUnixSupport;
+
+namespace System.IO.Abstractions.Benchmarks
+{
+    [RPlotExporter]
+    [MemoryDiagnoser]
+    public class MockFileSystemBenchmarks
+    {
+        private readonly Dictionary<string, MockFileData> testData = CreateTestData();
+
+        private static Dictionary<string, MockFileData> CreateTestData()
+        {
+            var filesCount = 100000;
+            var maxDirectoryDepth = 8;
+            return Enumerable.Range(0, filesCount).ToDictionary(
+                i => XFS.Path(@$"C:\{string.Join(@"\", Enumerable.Range(0, i % maxDirectoryDepth + 1).Select(i => i.ToString()))}\{i}.bin"),
+                i => new MockFileData(i.ToString()));
+        }
+
+        [Benchmark]
+        public MockFileSystem MockFileSystem_Constructor() => new MockFileSystem(testData);
+    }
+}

benchmarks/System.IO.Abstractions.Benchmarks/Program.cs

@@ -1,12 +1,13 @@
 namespace System.IO.Abstractions.Benchmarks
 {
     using BenchmarkDotNet.Running;
+    using System.Reflection;
 
     class Program
     {
         public static void Main(string[] args)
         {
-            BenchmarkRunner.Run<FileSystemAbstractionBenchmarks>();
+            BenchmarkRunner.Run(typeof(Program).Assembly);
         }
     }
 }

benchmarks/System.IO.Abstractions.Benchmarks/System.IO.Abstractions.Benchmarks.csproj

@@ -14,6 +14,7 @@
 	</PropertyGroup>
 	<ItemGroup>
 		<ProjectReference Include="../../src/System.IO.Abstractions/System.IO.Abstractions.csproj" />
+		<ProjectReference Include="../../src/System.IO.Abstractions.TestingHelpers/System.IO.Abstractions.TestingHelpers.csproj" />
 	</ItemGroup>
 	<ItemGroup>
 		<PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies.net461" Version="1.0.0">

src/System.IO.Abstractions.TestingHelpers/MockFileSystem.cs

@@ -13,7 +13,7 @@ public class MockFileSystem : IFileSystem, IMockFileDataAccessor
         private const string DEFAULT_CURRENT_DIRECTORY = @"C:\";
         private const string TEMP_DIRECTORY = @"C:\temp";
 
-        private readonly IDictionary<string, MockFileData> files;
+        private readonly IDictionary<string, FileSystemEntry> files;
         private readonly PathVerifier pathVerifier;
 
         public MockFileSystem() : this(null) { }
@@ -33,7 +33,7 @@ public MockFileSystem(IDictionary<string, MockFileData> files, string currentDir
 
             StringOperations = new StringOperations(XFS.IsUnixPlatform());
             pathVerifier = new PathVerifier(this);
-            this.files = new Dictionary<string, MockFileData>(StringOperations.Comparer);
+            this.files = new Dictionary<string, FileSystemEntry>(StringOperations.Comparer);
 
             Path = new MockPath(this, defaultTempDirectory);
             File = new MockFile(this);
@@ -101,10 +101,9 @@ private string GetPathWithCorrectDirectoryCapitalization(string fullPath)
                 int lastSeparator = leftHalf.LastIndexOf(Path.DirectorySeparatorChar);
                 leftHalf = lastSeparator > 0 ? leftHalf.Substring(0, lastSeparator) : leftHalf;
 
-                if (Directory.Exists(leftHalf))
+                if (DirectoryExistsWithoutFixingPath(leftHalf))
                 {
-                    leftHalf = Path.GetFullPath(leftHalf).TrimSlashes();
-                    string baseDirectory = AllDirectories.First(dir => StringOperations.Equals(dir, leftHalf));
+                    string baseDirectory = files[leftHalf].Path;
                     return baseDirectory + Path.DirectorySeparatorChar + rightHalf;
                 }
             }
@@ -121,7 +120,7 @@ public MockFileData GetFile(string path)
         private void SetEntry(string path, MockFileData mockFile)
         {
             path = FixPath(path, true).TrimSlashes();
-            files[path] = mockFile;
+            files[path] = new FileSystemEntry { Path = path, Data = mockFile };
         }
 
         public void AddFile(string path, MockFileData mockFile)
@@ -145,7 +144,7 @@ public void AddFile(string path, MockFileData mockFile)
 
                 var directoryPath = Path.GetDirectoryName(fixedPath);
 
-                if (!Directory.Exists(directoryPath))
+                if (!DirectoryExistsWithoutFixingPath(directoryPath))
                 {
                     AddDirectory(directoryPath);
                 }
@@ -190,7 +189,7 @@ public void AddDirectory(string path)
                 while ((lastIndex = StringOperations.IndexOf(fixedPath, separator, lastIndex + 1)) > -1)
                 {
                     var segment = fixedPath.Substring(0, lastIndex + 1);
-                    if (!Directory.Exists(segment))
+                    if (!DirectoryExistsWithoutFixingPath(segment))
                     {
                         SetEntry(segment, new MockDirectoryData());
                     }
@@ -333,7 +332,7 @@ public IEnumerable<string> AllFiles
             {
                 lock (files)
                 {
-                    return files.Where(f => !f.Value.IsDirectory).Select(f => f.Key).ToArray();
+                    return files.Where(f => !f.Value.Data.IsDirectory).Select(f => f.Key).ToArray();
                 }
             }
         }
@@ -344,7 +343,7 @@ public IEnumerable<string> AllDirectories
             {
                 lock (files)
                 {
-                    return files.Where(f => f.Value.IsDirectory).Select(f => f.Key).ToArray();
+                    return files.Where(f => f.Value.Data.IsDirectory).Select(f => f.Key).ToArray();
                 }
             }
         }
@@ -358,9 +357,23 @@ private MockFileData GetFileWithoutFixingPath(string path)
         {
             lock (files)
             {
-                files.TryGetValue(path, out var result);
-                return result;
+                return files.TryGetValue(path, out var result) ? result.Data : null;
             }
         }
+
+        private bool DirectoryExistsWithoutFixingPath(string path)
+        {
+            lock (files)
+            {
+                return files.TryGetValue(path, out var result) && result.Data.IsDirectory;
+            }
+        }
+
+        [Serializable]
+        private class FileSystemEntry
+        {
+            public string Path { get; set; }
+            public MockFileData Data { get; set; }
+        }
     }
 }

tests/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
 using System.Text;