[release/11.0] Disable file locking by default on iOS and tvOS

src/libraries/System.ComponentModel.Composition/tests/System/ComponentModel/Composition/Hosting/AssemblyCatalogTests.cs

@@ -174,7 +174,7 @@ public void Constructor1_ValueAsCodebaseArgument_ShouldSetAssemblyProperty()
             });
         }
 
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public void Constructor1_LockedFileAsCodeBaseArgument_ShouldThrowFileLoad()
         {
             AssemblyCatalogConstructorTests.Constructor_LockedFileAsCodeBaseArgument_ShouldThrowIOException((s) =>
@@ -273,7 +273,7 @@ public void Constructor2_ValueAsCodebaseArgument_ShouldSetAssemblyProperty()
             });
         }
 
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public void Constructor2_LockedFileAsCodeBaseArgument_ShouldThrowFileLoad()
         {
             AssemblyCatalogConstructorTests.Constructor_LockedFileAsCodeBaseArgument_ShouldThrowIOException((s) =>
@@ -371,7 +371,7 @@ public void Constructor3_ValueAsCodebaseArgument_ShouldSetAssemblyProperty()
             });
         }
 
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public void Constructor3_LockedFileAsCodeBaseArgument_ShouldThrowFileLoad()
         {
             AssemblyCatalogConstructorTests.Constructor_LockedFileAsCodeBaseArgument_ShouldThrowIOException((s) =>
@@ -468,7 +468,7 @@ public void Constructor4_ValueAsCodebaseArgument_ShouldSetAssemblyProperty()
             });
         }
 
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public void Constructor4_LockedFileAsCodeBaseArgument_ShouldThrowFileLoad()
         {
             AssemblyCatalogConstructorTests.Constructor_LockedFileAsCodeBaseArgument_ShouldThrowIOException((s) =>

src/libraries/System.IO.IsolatedStorage/tests/System/IO/IsolatedStorage/OpenFileTests.cs

@@ -66,7 +66,7 @@ public void OpenFile_RaisesIsolatedStorageException()
             }
         }
 
-        [Fact]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public void OpenFile_PassesFileShare()
         {
             TestHelper.WipeStores();

src/libraries/System.IO.MemoryMappedFiles/tests/MemoryMappedFile.CreateFromFile.Tests.cs

@@ -743,8 +743,7 @@ public void FileInUse_CreateFromFile_FailsWithExistingReadWriteMap()
         /// <summary>
         /// Test exceptional behavior when trying to create a map for a non-shared file that's currently in use.
         /// </summary>
-        [Fact]
-        [SkipOnPlatform(TestPlatforms.Browser, "the emscripten implementation ignores FileShare.None")]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public void FileInUse_CreateFromFile_FailsWithExistingNoShareFile()
         {
             // Already opened with a FileStream

src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Unix.cs

@@ -34,8 +34,11 @@ public sealed partial class SafeFileHandle : SafeHandleZeroOrMinusOneIsInvalid
             UnixFileMode.OtherRead |
             UnixFileMode.OtherWrite;
 
-        internal static bool DisableFileLocking { get; } = OperatingSystem.IsBrowser() || OperatingSystem.IsWasi()// #40065: Emscripten does not support file locking
-            || AppContextConfigHelper.GetBooleanConfig("System.IO.DisableFileLocking", "DOTNET_SYSTEM_IO_DISABLEFILELOCKING", defaultValue: false);
+        internal static bool DisableFileLocking { get; } = OperatingSystem.IsBrowser() || OperatingSystem.IsWasi() // #40065: Emscripten does not support file locking
+            || AppContextConfigHelper.GetBooleanConfig(
+                "System.IO.DisableFileLocking",
+                "DOTNET_SYSTEM_IO_DISABLEFILELOCKING",
+                defaultValue: (OperatingSystem.IsIOS() && !OperatingSystem.IsMacCatalyst()) || OperatingSystem.IsTvOS());
 
         // not using bool? as it's not thread safe
         private NullableBool _supportsRandomAccess /* = NullableBool.Undefined */;

src/libraries/System.Runtime/tests/System.IO.FileSystem.Tests/DisabledFileLockingTests/DisabledFileLockingSwitchTests.cs

@@ -11,7 +11,10 @@ public class DisabledFileLockingSwitchTests
         [Fact]
         public static void ConfigSwitchIsHonored()
         {
-            Assert.Equal(OperatingSystem.IsWindows(), PlatformDetection.IsFileLockingEnabled);
+            bool expected = OperatingSystem.IsWindows() ||
+                (OperatingSystem.IsIOS() && !OperatingSystem.IsMacCatalyst()) ||
+                OperatingSystem.IsTvOS();
+            Assert.Equal(expected, PlatformDetection.IsFileLockingEnabled);
         }
     }
 }

src/libraries/System.Runtime/tests/System.IO.FileSystem.Tests/DisabledFileLockingTests/System.IO.FileSystem.DisabledFileLocking.Tests.csproj

@@ -38,6 +38,10 @@
     <TrimmerRootDescriptor Condition="'$(TargetsAppleMobile)' == 'true' and '$(EnableAggressiveTrimming)' == 'true' and '$(UseNativeAotRuntime)' != 'true'" Include="$(MSBuildThisFileDirectory)ILLink.Descriptors.xml" />
   </ItemGroup>
   <ItemGroup>
-    <RuntimeHostConfigurationOption Include="System.IO.DisableFileLocking" Value="true" />
+    <!-- The default is 'disabled' for iOS and tvOS, but these platforms technically support locking, so enable file locking here to test the non-default scenario -->
+    <RuntimeHostConfigurationOption Include="System.IO.DisableFileLocking" Value="false"
+                                    Condition="'$(TargetOS)' == 'ios' or '$(TargetOS)' == 'iossimulator' or '$(TargetOS)' == 'tvos' or '$(TargetOS)' == 'tvossimulator'" />
+    <RuntimeHostConfigurationOption Include="System.IO.DisableFileLocking" Value="true"
+                                    Condition="'$(TargetOS)' != 'ios' and '$(TargetOS)' != 'iossimulator' and '$(TargetOS)' != 'tvos' and '$(TargetOS)' != 'tvossimulator'" />
   </ItemGroup>
 </Project>

src/libraries/System.Runtime/tests/System.IO.FileSystem.Tests/FileLockingDefaults.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace System.IO.Tests
+{
+    public class FileLockingDefaults
+    {
+        [Fact]
+        [PlatformSpecific(TestPlatforms.iOS | TestPlatforms.tvOS)]
+        public void FileLockingDisabledByDefault()
+        {
+            Assert.False(PlatformDetection.IsFileLockingEnabled);
+        }
+
+        [Fact]
+        [PlatformSpecific(TestPlatforms.MacCatalyst)]
+        public void FileLockingEnabledByDefault()
+        {
+            Assert.True(PlatformDetection.IsFileLockingEnabled);
+        }
+    }
+}

src/libraries/System.Runtime/tests/System.IO.FileSystem.Tests/System.IO.FileSystem.Tests.csproj

@@ -210,6 +210,7 @@
     <Compile Include="File\ReadWriteAllText.cs" />
     <Compile Include="File\ReadWriteAllLines.cs" />
     <Compile Include="File\SymbolicLinks.cs" />
+    <Compile Include="FileLockingDefaults.cs" />
     <Compile Include="TestData.cs" />
     <Compile Include="UnseekableFileStream.cs" />
     <Compile Include="FSAssert.cs" />

src/libraries/System.Runtime/tests/System.Reflection.Tests/AssemblyNameTests.cs

@@ -303,8 +303,7 @@ public static void GetAssemblyName()
             }
         }
 
-        [Fact]
-        [SkipOnPlatform(TestPlatforms.Browser, "File locking is not respected")]
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled))]
         public static void GetAssemblyName_LockedFile()
         {
             using (var tempFile = new TempFile(Path.GetTempFileName(), 100))