Remove AppContextDefaultValues/AccessibilitySwitches values from NetFX (dead code) (#9866)

* Remove AppContextDefaultValues/AccessibilitySwitches values from NetFX (dead code)

* Constrain CS0436 to LocalAppContext; use proper locking scheme mechanism

* Clean up CS0436 warning suppressions from the separate context files

* Change LocalAppContext from instance/partial to static class

Author: h3xds1nz

src/Microsoft.DotNet.Wpf/src/Common/src/System/AppContextDefaultValues.cs

@@ -2,17 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-// There are cases where we have multiple assemblies that are going to import this file and 
-// if they are going to also have InternalsVisibleTo between them, there will be a compiler warning
-// that the type is found both in the source and in a referenced assembly. The compiler will prefer 
-// the version of the type defined in the source
-//
-// In order to disable the warning for this type we are disabling this warning for this entire file.
-#pragma warning disable 436
-
-using System;
-using System.Collections.Generic;
-
 namespace System
 {
     internal static partial class AppContextDefaultValues
@@ -182,15 +171,11 @@ private static bool TryParseFrameworkName(String frameworkName, out String ident
             return true;
         }
 #endif
-        // This is a partial method. Platforms (such as Desktop) can provide an implementation of it that will read override value
-        // from whatever mechanism is available on that platform. If no implementation is provided, the compiler is going to remove the calls
-        // to it from the code
-        static partial void TryGetSwitchOverridePartial(string switchName, ref bool overrideFound, ref bool overrideValue);
 
+        /// <summary>
         /// This is a partial method. This method is responsible for populating the default values based on a TFM.
         /// It is partial because each library should define this method in their code to contain their defaults.
+        /// </summary> 
         static partial void PopulateDefaultValuesPartial(string platformIdentifier, string profile, int targetFrameworkVersion);
     }
 }
-
-#pragma warning restore 436

src/Microsoft.DotNet.Wpf/src/Common/src/System/LocalAppContext.cs

@@ -3,47 +3,58 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Runtime.CompilerServices;
-using System.Threading;
 using System.Collections.Generic;
+using System.Threading;
 
 namespace System
 {
-// error CS0436: When building PresentationFramework, the type 'LocalAppContext' 
-// conflicts with the imported type 'LocalAppContext' in 'PresentationCore
-#pragma warning disable 436
-    internal partial class LocalAppContext
+    internal static class LocalAppContext
     {
-        private static Dictionary<string, bool> s_switchMap = new Dictionary<string, bool>();
-        private static readonly object s_syncLock = new object();
+        /// <summary>
+        /// Holds the switch names and their values. In case it is modified outside <see cref="DefineSwitchDefault"/>,
+        /// proper thread synchronization is required as the switch state can be queried from any thread.
+        /// </summary>
+        private static readonly Dictionary<string, bool> s_switchMap = new();
+#if !NETFX
+        private static readonly Lock s_syncLock = new();
+#else
+        private static readonly object s_syncLock = new();
+#endif
 
         private static bool DisableCaching { get; set; }
 
         static LocalAppContext()
         {
+            // When building PresentationFramework, 'LocalAppContext' from WindowsBase.dll conflicts
+            // with 'LocalAppContext' from PresentationCore.dll since there is InternalsVisibleTo set
+#pragma warning disable CS0436 // Type conflicts with imported type
+
             // Populate the default values of the local app context 
             AppContextDefaultValues.PopulateDefaultValues();
 
+#pragma warning restore CS0436 // Type conflicts with imported type
+
             // Cache the value of the switch that help with testing
             DisableCaching = IsSwitchEnabled(@"TestSwitch.LocalAppContext.DisableCaching");
         }
 
         public static bool IsSwitchEnabled(string switchName)
         {
-            if (System.AppContext.TryGetSwitch(switchName, out var isEnabledCentrally))
+            if (AppContext.TryGetSwitch(switchName, out bool isEnabledCentrally))
             {
                 // we found the switch, so return whatever value it has
                 return isEnabledCentrally;
             }
-            // if we could not get the value from the central authority, try the local storage.
 
+            // if we could not get the value from the central authority, try the local storage.
             return IsSwitchEnabledLocal(switchName);
         }
 
         private static bool IsSwitchEnabledLocal(string switchName)
         {
             // read the value from the set of local defaults
             bool isEnabled, isPresent;
-            lock (s_switchMap)
+            lock (s_syncLock)
             {
                 isPresent = s_switchMap.TryGetValue(switchName, out isEnabled);
             }
@@ -62,20 +73,22 @@ private static bool IsSwitchEnabledLocal(string switchName)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static bool GetCachedSwitchValue(string switchName, ref int switchValue)
         {
-            if (switchValue < 0) return false;
-            if (switchValue > 0) return true;
+            if (switchValue < 0)
+                return false;
+            if (switchValue > 0)
+                return true;
 
             return GetCachedSwitchValueInternal(switchName, ref switchValue);
         }
 
         private static bool GetCachedSwitchValueInternal(string switchName, ref int switchValue)
         {
-            if (LocalAppContext.DisableCaching)
+            if (DisableCaching)
             {
-                return LocalAppContext.IsSwitchEnabled(switchName);
+                return IsSwitchEnabled(switchName);
             }
 
-            bool isEnabled = LocalAppContext.IsSwitchEnabled(switchName);
+            bool isEnabled = IsSwitchEnabled(switchName);
             switchValue = isEnabled ? 1 /*true*/ : -1 /*false*/;
             return isEnabled;
         }
@@ -90,5 +103,4 @@ internal static void DefineSwitchDefault(string switchName, bool initialValue)
             s_switchMap[switchName] = initialValue;
         }
     }
-#pragma warning restore 436
 }

src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/MS/Internal/BuildTasksAppContextSwitches.cs

@@ -7,11 +7,6 @@
 
 namespace MS.Internal
 {
-    // WPF's builds are seeing warnings as a result of using LocalAppContext in mutliple assemblies.
-    // that have internalsVisibleTo attribute set between them - which results in the warning.
-    // We don't have a way of suppressing this warning effectively until the shared copies of LocalAppContext and
-    // AppContextDefaultValues have pragmas added to suppress warning 436
-#pragma warning disable 436
     internal static class BuildTasksAppContextSwitches
     {
         #region DoNotUseSha256ForMarkupCompilerChecksumAlgorithm
@@ -30,5 +25,4 @@ public static bool DoNotUseSha256ForMarkupCompilerChecksumAlgorithm
 
         #endregion
     }
-#pragma warning restore 436
 }

src/Microsoft.DotNet.Wpf/src/PresentationBuildTasks/System/AppContextDefaultValues.cs

@@ -2,45 +2,31 @@
 // 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.Windows;
 using MS.Internal;
 
 namespace System
 {
-    // WPF's builds are seeing warnings as a result of using LocalAppContext in mutliple assemblies.
-    // that have internalsVisibleTo attribute set between them - which results in the warning.
-    // We don't have a way of suppressing this warning effectively until the shared copies of LocalAppContext and
-    // AppContextDefaultValues have pragmas added to suppress warning 436
-#pragma warning disable 436
     internal static partial class AppContextDefaultValues
     {
+        /// <summary>
+        /// This is a partial method. This method is responsible for populating the default values based on a TFM.
+        /// It is partial because each library should define this method in their code to contain their defaults.
+        /// </summary> 
         static partial void PopulateDefaultValuesPartial(string platformIdentifier, string profile, int targetFrameworkVersion)
         {
             switch (platformIdentifier)
             {
                 case ".NETFramework":
+                    if (targetFrameworkVersion <= 40701)
                     {
-                        if (targetFrameworkVersion <= 40701)
-                        {
-                            LocalAppContext.DefineSwitchDefault(BuildTasksAppContextSwitches.DoNotUseSha256ForMarkupCompilerChecksumAlgorithmSwitchName, true);
-                        }
-
-                        break;
+                        LocalAppContext.DefineSwitchDefault(BuildTasksAppContextSwitches.DoNotUseSha256ForMarkupCompilerChecksumAlgorithmSwitchName, true);
                     }
+                    break;
 
                 case ".NETCoreApp":
-                    {
-                        InitializeNetFxSwitchDefaultsForNetCoreRuntime();
-                    }
+                    LocalAppContext.DefineSwitchDefault(BuildTasksAppContextSwitches.DoNotUseSha256ForMarkupCompilerChecksumAlgorithmSwitchName, false);
                     break;
             }
         }
-
-        private static void InitializeNetFxSwitchDefaultsForNetCoreRuntime()
-        {
-            LocalAppContext.DefineSwitchDefault(BuildTasksAppContextSwitches.DoNotUseSha256ForMarkupCompilerChecksumAlgorithmSwitchName, false);
-        }
     }
-#pragma warning restore 436
 }

src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/CoreAppContextSwitches.cs

@@ -2,20 +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.Runtime.CompilerServices;
 using System.Windows;
 
 namespace MS.Internal
 {
-    // WPF's builds are seeing new warnings as as result of using LocalAppContext in PresentationFramework, PresentationCore and WindowsBase.
-    // These binaries have internalsVisibleTo attribute set between them - which results in the warning.
-    // We don't have a way of suppressing this warning effectively until the shared copies of LocalAppContext and
-    // AppContextDefaultValues have pragmas added to suppress warning 436
-#pragma warning disable 436
     internal static class CoreAppContextSwitches
     {
         #region DoNotScaleForDpiChanges
@@ -411,5 +403,4 @@ public static bool DisableSpecialCharacterLigature
         #endregion
 
     }
-#pragma warning restore 436
 }

src/Microsoft.DotNet.Wpf/src/PresentationCore/System/AppContextDefaultValues.cs

@@ -2,50 +2,17 @@
 // 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.Windows;
 using MS.Internal;
 
 namespace System
 {
-    // WPF's builds are seeing new warnings as as result of using LocalAppContext in PresentationFramework, PresentationCore and WindowsBase. 
-    // These binaries have internalsVisibleTo attribute set between them - which results in the warning. 
-    // We don't have a way of suppressing this warning effectively until the shared copies of LocalAppContext and 
-    // AppContextDefaultValues have pragmas added to suppress warning 436
-#pragma warning disable 436
     internal static partial class AppContextDefaultValues
     {
+        /// <summary>
+        /// This is a partial method. This method is responsible for populating the default values based on a TFM.
+        /// It is partial because each library should define this method in their code to contain their defaults.
+        /// </summary> 
         static partial void PopulateDefaultValuesPartial(string platformIdentifier, string profile, int targetFrameworkVersion)
-        {
-            switch (platformIdentifier)
-            {
-                case ".NETFramework":
-                    {
-                        if (targetFrameworkVersion <= 40601)
-                        {
-                            LocalAppContext.DefineSwitchDefault(CoreAppContextSwitches.DoNotScaleForDpiChangesSwitchName, true);
-                        }
-
-                        if (targetFrameworkVersion <= 40602)
-                        {
-                            LocalAppContext.DefineSwitchDefault(CoreAppContextSwitches.OverrideExceptionWithNullReferenceExceptionName, true);
-                        }
-
-                        if (targetFrameworkVersion <= 40702)
-                        {
-                            LocalAppContext.DefineSwitchDefault(CoreAppContextSwitches.DoNotUsePresentationDpiCapabilityTier2OrGreaterSwitchName, true);
-                        }
-
-                        break;
-                    }
-                case ".NETCoreApp":
-                    {
-                        InitializeNetFxSwitchDefaultsForNetCoreRuntime();
-                    }
-                    break;
-            }
-        }
-
-        private static void InitializeNetFxSwitchDefaultsForNetCoreRuntime()
         {
             LocalAppContext.DefineSwitchDefault(CoreAppContextSwitches.DoNotScaleForDpiChangesSwitchName, false);
             LocalAppContext.DefineSwitchDefault(CoreAppContextSwitches.OverrideExceptionWithNullReferenceExceptionName, false);
@@ -64,5 +31,4 @@ private static void InitializeNetFxSwitchDefaultsForNetCoreRuntime()
             LocalAppContext.DefineSwitchDefault(CoreAppContextSwitches.DisableSpecialCharacterLigatureSwitchName, false);
         }
     }
-#pragma warning restore 436
 }

src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/FrameworkAppContextSwitches.cs

@@ -2,22 +2,15 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-
-using MS.Internal.PresentationFramework.Interop;
-using System;
 using System.Runtime.CompilerServices;
-using System.Windows;
+using System;
+
+// When building PresentationFramework, 'LocalAppContext' from WindowsBase.dll conflicts
+// with 'LocalAppContext' from PresentationCore.dll since there is InternalsVisibleTo set
+#pragma warning disable CS0436 // Type conflicts with imported type
 
 namespace MS.Internal
 {
-    // There are cases where we have multiple assemblies that are going to import this file and
-    // if they are going to also have InternalsVisibleTo between them, there will be a compiler warning
-    // that the type is found both in the source and in a referenced assembly. The compiler will prefer
-    // the version of the type defined in the source
-    //
-    // In order to disable the warning for this type we are disabling this warning for this entire file.
-    #pragma warning disable 436
-
     internal static class FrameworkAppContextSwitches
     {
         internal const string DoNotApplyLayoutRoundingToMarginsAndBorderThicknessSwitchName = "Switch.MS.Internal.DoNotApplyLayoutRoundingToMarginsAndBorderThickness";
@@ -156,6 +149,6 @@ public static bool DisableDynamicResourceOptimization
             }
         }
     }
-
-#pragma warning restore 436
 }
+
+#pragma warning restore CS0436 // Type conflicts with imported type