Change IsolatedStorageFile path for mobile

src/libraries/System.IO.IsolatedStorage/src/System.IO.IsolatedStorage.csproj

@@ -14,7 +14,6 @@
     <Compile Include="System\IO\IsolatedStorage\IsolatedStorage.cs" />
     <Compile Include="System\IO\IsolatedStorage\IsolatedStorageScope.cs" />
     <Compile Include="System\IO\IsolatedStorage\Helper.cs" />
-    <Compile Include="System\IO\IsolatedStorage\Helper.Win32Unix.cs" />
     <Compile Include="System\IO\IsolatedStorage\INormalizeForIsolatedStorage.cs" />
     <Compile Include="$(CommonPath)System\Security\IdentityHelper.cs"
              Link="Common\System\Security\IdentityHelper.cs" />

src/libraries/System.IO.IsolatedStorage/src/System/IO/IsolatedStorage/Helper.AnyMobile.cs

@@ -5,6 +5,57 @@ namespace System.IO.IsolatedStorage
 {
     internal static partial class Helper
     {
+        // we're using a different directory name for compatibility with legacy Xamarin
         public const string IsolatedStorageDirectoryName = ".isolated-storage";
+
+        internal static string GetDataDirectory(IsolatedStorageScope scope)
+        {
+            // This is the relevant special folder for the given scope plus IsolatedStorageDirectoryName.
+            // It is meant to replicate the behavior of the VM ComIsolatedStorage::GetRootDir().
+            //
+            // In legacy Xamarin for Roaming Scope we were using Environment.SpecialFolder.LocalApplicationData
+            // In .Net 7 for Roaming Scope we are using Environment.SpecialFolder.ApplicationData
+            // e.g. .Net 7  path = /data/user/0/{packageName}/files/.isolated-storage/{hash}/{hash}/AppFiles/
+            // e.g. Xamarin path = /data/user/0/{packageName}/files/.config/.isolated-storage"
+            //
+            // Since we shipped that behavior as part of .NET 7 we can't change this now or upgraded apps wouldn't find their files anymore.
+            // We need to look for an existing directory first before using the legacy Xamarin approach.
+
+            Environment.SpecialFolder specialFolder =
+            IsMachine(scope) ? Environment.SpecialFolder.CommonApplicationData : // e.g. /usr/share;
+            IsRoaming(scope) ? Environment.SpecialFolder.ApplicationData : // e.g. /data/user/0/{packageName}/files/.config;
+            Environment.SpecialFolder.LocalApplicationData; // e.g. /data/user/0/{packageName}/files;
+
+            string dataDirectory = Environment.GetFolderPath(specialFolder);
+            dataDirectory = Path.Combine(dataDirectory, IsolatedStorageDirectoryName);
+            if (Directory.Exists(dataDirectory))
+            {
+                return dataDirectory;
+            }
+            // Otherwise return legacy xamarin path
+            else
+            {
+                specialFolder =
+                IsMachine(scope) ? Environment.SpecialFolder.CommonApplicationData :
+                IsRoaming(scope) ? Environment.SpecialFolder.LocalApplicationData:
+                Environment.SpecialFolder.ApplicationData;
+
+                dataDirectory = Environment.GetFolderPath(specialFolder, Environment.SpecialFolderOption.Create);
+                dataDirectory = Path.Combine(dataDirectory, IsolatedStorageDirectoryName);
+            }
+
+            return dataDirectory;
+        }
+
+        internal static string GetRandomDirectory(string rootDirectory, IsolatedStorageScope _)
+        {
+            // In legacy Xamarin we didn't have a random directory inside of the isolated storage root for each app,
+            // we tried to preserve that in https://github.com/dotnet/runtime/pull/75541 but the fix wasn't complete enough
+            // and we still created random directories when not using the Roaming scope.
+            //
+            // Since we shipped that behavior as part of .NET 7 we can't change this now or upgraded apps wouldn't find their files anymore.
+            // We need to look for an existing random directory first before using the plain root directory.
+            return GetExistingRandomDirectory(rootDirectory) ?? rootDirectory;
+        }
     }
 }

src/libraries/System.IO.IsolatedStorage/src/System/IO/IsolatedStorage/Helper.NonMobile.cs

@@ -1,10 +1,68 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Threading;
+using System.Security;
+
 namespace System.IO.IsolatedStorage
 {
     internal static partial class Helper
     {
         public const string IsolatedStorageDirectoryName = "IsolatedStorage";
+
+        internal static string GetDataDirectory(IsolatedStorageScope scope)
+        {
+            // This is the relevant special folder for the given scope plus IsolatedStorageDirectoryName.
+            // It is meant to replicate the behavior of the VM ComIsolatedStorage::GetRootDir().
+
+            // (note that Silverlight used "CoreIsolatedStorage" for a directory name and did not support machine scope)
+
+            Environment.SpecialFolder specialFolder =
+            IsMachine(scope) ? Environment.SpecialFolder.CommonApplicationData : // e.g. C:\ProgramData
+            IsRoaming(scope) ? Environment.SpecialFolder.ApplicationData : // e.g. C:\Users\Joe\AppData\Roaming
+            Environment.SpecialFolder.LocalApplicationData; // e.g. C:\Users\Joe\AppData\Local
+
+            string dataDirectory = Environment.GetFolderPath(specialFolder, Environment.SpecialFolderOption.Create);
+            dataDirectory = Path.Combine(dataDirectory, IsolatedStorageDirectoryName);
+
+            return dataDirectory;
+        }
+
+        internal static string GetRandomDirectory(string rootDirectory, IsolatedStorageScope scope)
+        {
+            string? randomDirectory = GetExistingRandomDirectory(rootDirectory);
+            if (string.IsNullOrEmpty(randomDirectory))
+            {
+                using (Mutex m = CreateMutexNotOwned(rootDirectory))
+                {
+                    if (!m.WaitOne())
+                    {
+                        throw new IsolatedStorageException(SR.IsolatedStorage_Init);
+                    }
+
+                    try
+                    {
+                        randomDirectory = GetExistingRandomDirectory(rootDirectory);
+                        if (string.IsNullOrEmpty(randomDirectory))
+                        {
+                            // Someone else hasn't created the directory before we took the lock
+                            randomDirectory = Path.Combine(rootDirectory, Path.GetRandomFileName(), Path.GetRandomFileName());
+                            CreateDirectory(randomDirectory, scope);
+                        }
+                    }
+                    finally
+                    {
+                        m.ReleaseMutex();
+                    }
+                }
+            }
+
+            return randomDirectory;
+        }
+
+        private static Mutex CreateMutexNotOwned(string pathName)
+        {
+            return new Mutex(initiallyOwned: false, name: @"Global\" + IdentityHelper.GetStrongHashSuitableForObjectName(pathName));
+        }
     }
 }