Fix sharing violations caused by FileShare.Inherited

The FileShareOpen test has been failing sporadically with sharing violations.  It turns out the problem has to do with FileShare.Inheritable being included in the list of FileShare values to test.  If another test in the same process concurrently spawns a process while a FileShare.Inheritable file is open, that file's handle will be inherited into the child process, which will in turn keep the file in use for longer than the test expects.  When it then tries to re-open the file, it may encounter a sharing violation if the subsequent open is incompatible with the previous one's FileShare.

Author: stephentoub

src/System.IO.FileSystem/tests/File/Open.cs

@@ -32,12 +32,12 @@ public class File_Open_str_fm_fa_fs : FileStream_ctor_str_fm_fa_fs
     {
         protected override FileStream CreateFileStream(string path, FileMode mode)
         {
-            return File.Open(path, mode, mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete | FileShare.Inheritable);
+            return File.Open(path, mode, mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete);
         }
 
         protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access)
         {
-            return File.Open(path, mode, access, FileShare.ReadWrite | FileShare.Delete | FileShare.Inheritable);
+            return File.Open(path, mode, access, FileShare.ReadWrite | FileShare.Delete);
         }
 
         protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access, FileShare share)

src/System.IO.FileSystem/tests/FileInfo/Open.cs

@@ -65,12 +65,12 @@ public class FileInfo_Open_fm_fa_fs : FileStream_ctor_str_fm_fa_fs
     {
         protected override FileStream CreateFileStream(string path, FileMode mode)
         {
-            return new FileInfo(path).Open(mode, mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete | FileShare.Inheritable);
+            return new FileInfo(path).Open(mode, mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete);
         }
 
         protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access)
         {
-            return new FileInfo(path).Open(mode, access, FileShare.ReadWrite | FileShare.Delete | FileShare.Inheritable);
+            return new FileInfo(path).Open(mode, access, FileShare.ReadWrite | FileShare.Delete);
         }
 
         protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access, FileShare share)

src/System.IO.FileSystem/tests/FileStream/ctor_str_fm.cs

@@ -2,13 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.IO;
+using System.Diagnostics;
 using Xunit;
 
 namespace System.IO.Tests
 {
-    public class FileStream_ctor_str_fm : FileSystemTest
+    public class FileStream_ctor_str_fm : RemoteExecutorTestBase
     {
         protected virtual FileStream CreateFileStream(string path, FileMode mode)
         {

src/System.IO.FileSystem/tests/FileStream/ctor_str_fm_fa_fs.cs

@@ -23,11 +23,14 @@ public void InvalidShareThrows()
         private static readonly FileShare[] s_shares =
         {
             FileShare.None,
-            FileShare.Inheritable,
-            FileShare.Delete, FileShare.Delete | FileShare.Inheritable,
-            FileShare.Read, FileShare.Read | FileShare.Inheritable, FileShare.Read | FileShare.Delete, FileShare.Read | FileShare.Delete | FileShare.Inheritable,
-            FileShare.Write, FileShare.Write | FileShare.Inheritable, FileShare.Write | FileShare.Delete, FileShare.Write | FileShare.Delete | FileShare.Inheritable,
-            FileShare.ReadWrite, FileShare.ReadWrite | FileShare.Inheritable, FileShare.ReadWrite | FileShare.Delete, FileShare.ReadWrite | FileShare.Delete | FileShare.Inheritable
+            FileShare.Delete,
+            FileShare.Read, FileShare.Read | FileShare.Delete,
+            FileShare.Write, FileShare.Write | FileShare.Delete,
+            FileShare.ReadWrite, FileShare.ReadWrite | FileShare.Delete
+
+            // Does not include FileShare.Inheritable, as doing so when other tests concurrently spawn processes
+            // results in those file handles being inherited, which then keeps the file open longer
+            // than expected by the test, resulting in subsequent sharing violations.
         };
 
         [Fact]
@@ -54,6 +57,25 @@ public void FileShareOpen()
             }
         }
 
+        [Fact]
+        public void FileShareOpen_Inheritable()
+        {
+            RemoteInvoke(() =>
+            {
+                int i = 0;
+                foreach (FileAccess access in new[] { FileAccess.ReadWrite, FileAccess.Write, FileAccess.Read })
+                {
+                    foreach (FileShare share in s_shares)
+                    {
+                        string fileName = GetTestFilePath(i++);
+                        CreateFileStream(fileName, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete).Dispose();
+                        CreateFileStream(fileName, FileMode.Open, access, share | FileShare.Inheritable).Dispose();
+                    }
+                }
+                return SuccessExitCode;
+            }).Dispose();
+        }
+
         [Fact]
         public void FileShareCreate()
         {