fix: file stream sharing

src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFile.cs

@@ -677,7 +677,7 @@ private FileSystemStream OpenInternal(
         }
         mockFileDataAccessor.AdjustTimes(mockFileData, timeAdjustments);
 
-        return new MockFileStream(mockFileDataAccessor, path, mode, access, options);
+        return new MockFileStream(mockFileDataAccessor, path, mode, access, FileShare.Read, options);
     }
 
     /// <inheritdoc />

src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFileStream.cs

@@ -2,6 +2,7 @@
 using System.Threading;
 using System.Runtime.Versioning;
 using System.Security.AccessControl;
+using System.Collections.Concurrent;
 
 namespace System.IO.Abstractions.TestingHelpers;
 
@@ -32,16 +33,19 @@ public NullFileSystemStream() : base(Null, ".", true)
     private readonly IMockFileDataAccessor mockFileDataAccessor;
     private readonly string path;
     private readonly FileAccess access = FileAccess.ReadWrite;
+    private readonly FileShare share = FileShare.Read;
     private readonly FileOptions options;
     private readonly MockFileData fileData;
     private bool disposed;
+    private static ConcurrentDictionary<string, byte> _fileShareNoneStreams = [];
 
     /// <inheritdoc />
     public MockFileStream(
         IMockFileDataAccessor mockFileDataAccessor,
         string path,
         FileMode mode,
         FileAccess access = FileAccess.ReadWrite,
+        FileShare share = FileShare.Read,
         FileOptions options = FileOptions.None)
         : base(new MemoryStream(),
             path == null ? null : Path.GetFullPath(path),
@@ -54,6 +58,11 @@ public MockFileStream(
         this.path = path;
         this.options = options;
 
+        if (_fileShareNoneStreams.ContainsKey(path)) 
+        {
+            throw CommonExceptions.ProcessCannotAccessFileInUse(path);
+        }
+
         if (mockFileDataAccessor.FileExists(path))
         {
             if (mode.Equals(FileMode.CreateNew))
@@ -97,7 +106,15 @@ public MockFileStream(
             mockFileDataAccessor.AddFile(path, fileData);
         }
 
+        if (share is FileShare.None) 
+        {
+            if (!_fileShareNoneStreams.TryAdd(path, 0))
+            {
+                throw CommonExceptions.ProcessCannotAccessFileInUse(path);
+            }
+        }
         this.access = access;
+        this.share = share;
     }
 
     private static void ThrowIfInvalidModeAccess(FileMode mode, FileAccess access)
@@ -144,6 +161,10 @@ protected override void Dispose(bool disposing)
         {
             return;
         }
+        if (share is FileShare.None)
+        {
+            _fileShareNoneStreams.TryRemove(path, out _);
+        }
         InternalFlush();
         base.Dispose(disposing);
         OnClose();

src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFileStreamFactory.cs

@@ -41,25 +41,25 @@ public FileSystemStream New(string path, FileMode mode, FileAccess access)
 
     /// <inheritdoc />
     public FileSystemStream New(string path, FileMode mode, FileAccess access, FileShare share)
-        => new MockFileStream(mockFileSystem, path, mode, access);
+        => new MockFileStream(mockFileSystem, path, mode, access, share);
 
     /// <inheritdoc />
     public FileSystemStream New(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize)
-        => new MockFileStream(mockFileSystem, path, mode, access);
+        => new MockFileStream(mockFileSystem, path, mode, access, share);
 
     /// <inheritdoc />
     public FileSystemStream New(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, bool useAsync)
-        => new MockFileStream(mockFileSystem, path, mode, access);
+        => new MockFileStream(mockFileSystem, path, mode, access, share);
 
     /// <inheritdoc />
     public FileSystemStream New(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize,
         FileOptions options)
-        => new MockFileStream(mockFileSystem, path, mode, access, options);
+        => new MockFileStream(mockFileSystem, path, mode, access, share, options);
 
 #if FEATURE_FILESTREAM_OPTIONS
     /// <inheritdoc />
     public FileSystemStream New(string path, FileStreamOptions options)
-        => new MockFileStream(mockFileSystem, path, options.Mode, options.Access, options.Options);
+        => new MockFileStream(mockFileSystem, path, options.Mode, options.Access, options: options.Options);
 #endif
 
     /// <inheritdoc />

tests/TestableIO.System.IO.Abstractions.Api.Tests/Expected/TestableIO.System.IO.Abstractions.TestingHelpers_net472.txt

@@ -297,7 +297,7 @@ namespace System.IO.Abstractions.TestingHelpers
     [System.Serializable]
     public class MockFileStream : System.IO.Abstractions.FileSystemStream, System.IO.Abstractions.IFileSystemAclSupport
     {
-        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileOptions options = 0) { }
+        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileShare share = 1, System.IO.FileOptions options = 0) { }
         public override bool CanRead { get; }
         public override bool CanWrite { get; }
         public static System.IO.Abstractions.FileSystemStream Null { get; }

tests/TestableIO.System.IO.Abstractions.Api.Tests/Expected/TestableIO.System.IO.Abstractions.TestingHelpers_net6.0.txt

@@ -346,7 +346,7 @@ namespace System.IO.Abstractions.TestingHelpers
     [System.Serializable]
     public class MockFileStream : System.IO.Abstractions.FileSystemStream, System.IO.Abstractions.IFileSystemAclSupport
     {
-        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileOptions options = 0) { }
+        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileShare share = 1, System.IO.FileOptions options = 0) { }
         public override bool CanRead { get; }
         public override bool CanWrite { get; }
         public static System.IO.Abstractions.FileSystemStream Null { get; }

tests/TestableIO.System.IO.Abstractions.Api.Tests/Expected/TestableIO.System.IO.Abstractions.TestingHelpers_net8.0.txt

@@ -370,7 +370,7 @@ namespace System.IO.Abstractions.TestingHelpers
     [System.Serializable]
     public class MockFileStream : System.IO.Abstractions.FileSystemStream, System.IO.Abstractions.IFileSystemAclSupport
     {
-        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileOptions options = 0) { }
+        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileShare share = 1, System.IO.FileOptions options = 0) { }
         public override bool CanRead { get; }
         public override bool CanWrite { get; }
         public static System.IO.Abstractions.FileSystemStream Null { get; }

tests/TestableIO.System.IO.Abstractions.Api.Tests/Expected/TestableIO.System.IO.Abstractions.TestingHelpers_net9.0.txt

@@ -384,7 +384,7 @@ namespace System.IO.Abstractions.TestingHelpers
     [System.Serializable]
     public class MockFileStream : System.IO.Abstractions.FileSystemStream, System.IO.Abstractions.IFileSystemAclSupport
     {
-        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileOptions options = 0) { }
+        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileShare share = 1, System.IO.FileOptions options = 0) { }
         public override bool CanRead { get; }
         public override bool CanWrite { get; }
         public static System.IO.Abstractions.FileSystemStream Null { get; }

tests/TestableIO.System.IO.Abstractions.Api.Tests/Expected/TestableIO.System.IO.Abstractions.TestingHelpers_netstandard2.0.txt

@@ -297,7 +297,7 @@ namespace System.IO.Abstractions.TestingHelpers
     [System.Serializable]
     public class MockFileStream : System.IO.Abstractions.FileSystemStream, System.IO.Abstractions.IFileSystemAclSupport
     {
-        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileOptions options = 0) { }
+        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileShare share = 1, System.IO.FileOptions options = 0) { }
         public override bool CanRead { get; }
         public override bool CanWrite { get; }
         public static System.IO.Abstractions.FileSystemStream Null { get; }

tests/TestableIO.System.IO.Abstractions.Api.Tests/Expected/TestableIO.System.IO.Abstractions.TestingHelpers_netstandard2.1.txt

@@ -323,7 +323,7 @@ namespace System.IO.Abstractions.TestingHelpers
     [System.Serializable]
     public class MockFileStream : System.IO.Abstractions.FileSystemStream, System.IO.Abstractions.IFileSystemAclSupport
     {
-        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileOptions options = 0) { }
+        public MockFileStream(System.IO.Abstractions.TestingHelpers.IMockFileDataAccessor mockFileDataAccessor, string path, System.IO.FileMode mode, System.IO.FileAccess access = 3, System.IO.FileShare share = 1, System.IO.FileOptions options = 0) { }
         public override bool CanRead { get; }
         public override bool CanWrite { get; }
         public static System.IO.Abstractions.FileSystemStream Null { get; }

tests/TestableIO.System.IO.Abstractions.TestingHelpers.Tests/MockFileStreamTests.cs

@@ -390,4 +390,26 @@ async Task Act() =>
             await source.CopyToAsync(destination);
         await That(Act).Throws<NotSupportedException>();
     }
+
+    [Test]
+    public async Task MockFileStream_WhenExclusiveStreamOpen_ShouldThrowIOException()
+    {
+        var fileSystem = new MockFileSystem();
+        fileSystem.File.WriteAllText("foo.txt", "");
+        using (new MockFileStream(fileSystem, "foo.txt", FileMode.Open, FileAccess.Read, FileShare.None))
+        {
+            await That(() => new MockFileStream(fileSystem, "foo.txt", FileMode.Open, FileAccess.Read)).Throws<IOException>();
+        }
+    }
+
+    [Test]
+    public async Task MockFileStream_WhenExclusiveStreamClosed_ShouldNotThrow()
+    {
+        var fileSystem = new MockFileSystem();
+        fileSystem.File.WriteAllText("foo.txt", "");
+        var stream = new MockFileStream(fileSystem, "foo.txt", FileMode.Open, FileAccess.Read, FileShare.None);
+        stream.Dispose();
+
+        await That(() => new MockFileStream(fileSystem, "foo.txt", FileMode.Open, FileAccess.Read)).DoesNotThrow();
+    }
 }