Unwrap wrapped filesystems

src/Umbraco.Core/IO/FileSystemExtensions.cs

@@ -65,5 +65,33 @@ namespace Umbraco.Core.IO
             }
             fs.DeleteFile(tempFile);
         }
+
+        /// <summary>
+        /// Unwraps a filesystem.
+        /// </summary>
+        /// <remarks>
+        /// <para>A filesystem can be wrapped in a <see cref="FileSystemWrapper"/> (public) or a <see cref="ShadowWrapper"/> (internal),
+        /// and this method deals with the various wrappers and </para>
+        /// </remarks>
+        public static IFileSystem Unwrap(this IFileSystem filesystem)
+        {
+            var unwrapping = true;
+            while (unwrapping)
+            {
+                switch (filesystem)
+                {
+                    case FileSystemWrapper wrapper:
+                        filesystem = wrapper.InnerFileSystem;
+                        break;
+                    case ShadowWrapper shadow:
+                        filesystem = shadow.InnerFileSystem;
+                        break;
+                    default:
+                        unwrapping = false;
+                        break;
+                }
+            }
+            return filesystem;
+        }
     }
 }

src/Umbraco.Core/IO/FileSystemWrapper.cs

@@ -21,7 +21,7 @@ namespace Umbraco.Core.IO
             InnerFileSystem = innerFileSystem;
         }
 
-        public IFileSystem InnerFileSystem { get; internal set; }
+        internal IFileSystem InnerFileSystem { get; set; }
 
         public IEnumerable<string> GetDirectories(string path)
         {

src/Umbraco.Core/IO/ShadowWrapper.cs

@@ -75,6 +75,8 @@ namespace Umbraco.Core.IO
             }
         }
 
+        public IFileSystem InnerFileSystem => _innerFileSystem;
+
         private IFileSystem FileSystem
         {
             get

src/Umbraco.Tests/IO/FileSystemsTests.cs

@@ -86,6 +86,16 @@ namespace Umbraco.Tests.IO
             Assert.AreSame(fileSystem1, fileSystem2);
         }
 
+        [Test]
+        public void Can_Unwrap_MediaFileSystem()
+        {
+            var fileSystem = _factory.GetInstance<IMediaFileSystem>();
+            var unwrapped = fileSystem.Unwrap();
+            Assert.IsNotNull(unwrapped);
+            var physical = unwrapped as PhysicalFileSystem;
+            Assert.IsNotNull(physical);
+        }
+
         [Test]
         public void Can_Delete_MediaFiles()
         {