(cgallred) Fix-enumeration-handling

Author: yerudako

simpleProviderManaged/ActiveEnumeration.cs

@@ -19,6 +19,11 @@ public ActiveEnumeration(List<ProjectedFileInfo> fileInfos)
             this.MoveNext();
         }
 
+        /// <summary>
+        /// Indicates whether the current item is the first one in the enumeration.
+        /// </summary>
+        public bool IsCurrentFirst { get; private set; }
+
         /// <summary>
         /// true if Current refers to an element in the enumeration, false if Current is past the end of the collection
         /// </summary>
@@ -54,6 +59,8 @@ public void RestartEnumeration(
         public bool MoveNext()
         {
             this.IsCurrentValid = this.fileInfoEnumerator.MoveNext();
+            this.IsCurrentFirst = false;
+
             while (this.IsCurrentValid && this.IsCurrentHidden())
             {
                 this.IsCurrentValid = this.fileInfoEnumerator.MoveNext();
@@ -139,6 +146,7 @@ private bool IsCurrentHidden()
         private void ResetEnumerator()
         {
             this.fileInfoEnumerator = this.fileInfos.GetEnumerator();
+            this.IsCurrentFirst = true;
         }
     }
 }

simpleProviderManaged/EnvironmentHelper.cs

@@ -11,19 +11,16 @@ public static class EnvironmentHelper
     {
         public static bool IsFullSymlinkSupportAvailable()
         {
-            if (System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription.StartsWith(".NET Core"))
-            {
-                // Using registry instead of OSVersion due to https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getversionexa?redirectedfrom=MSDN.
-                // This code can be replaced with Environment.OSVersion on .NET Core 5 and higher.
-                int build = Convert.ToInt32(Microsoft.Win32.Registry.GetValue(
-                    @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion",
-                    "CurrentBuild",
-                    0));
+            // Using registry instead of OSVersion due to https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getversionexa?redirectedfrom=MSDN.
+            // This code can be replaced with Environment.OSVersion on .NET Core 5 and higher.
+            int build = Convert.ToInt32(Microsoft.Win32.Registry.GetValue(
+                @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion",
+                "CurrentBuild",
+                0));
 
-                if (build >= 19041)
-                {
-                    return true;
-                }
+            if (build >= 19041)
+            {
+                return true;
             }
 
             return false;

simpleProviderManaged/SimpleProvider.cs

@@ -370,6 +370,7 @@ internal HResult GetDirectoryEnumerationCallback(
             // Find the requested enumeration.  It should have been put there by StartDirectoryEnumeration.
             if (!this.activeEnumerations.TryGetValue(enumerationId, out ActiveEnumeration enumeration))
             {
+                Log.Fatal("      GetDirectoryEnumerationCallback {Result}", HResult.InternalError);
                 return HResult.InternalError;
             }
 
@@ -389,7 +390,6 @@ internal HResult GetDirectoryEnumerationCallback(
                 enumeration.TrySaveFilterString(filterFileName);
             }
 
-            bool entryAdded = false;
             HResult hr = HResult.Ok;
 
             while (enumeration.IsCurrentValid)
@@ -402,27 +402,35 @@ internal HResult GetDirectoryEnumerationCallback(
                     break;
                 }
 
+                // A provider adds entries to the enumeration buffer until it runs out, or until adding
+                // an entry fails. If adding an entry fails, the provider remembers the entry it couldn't
+                // add. ProjFS will call the GetDirectoryEnumerationCallback again, and the provider
+                // must resume adding entries, starting at the last one it tried to add. SimpleProvider
+                // remembers the entry it couldn't add simply by not advancing its ActiveEnumeration.
                 if (AddFileInfoToEnum(enumResult, fileInfo, targetPath))
                 {
-                    entryAdded = true;
                     enumeration.MoveNext();
                 }
                 else
                 {
-                    if (entryAdded)
-                    {
-                        hr = HResult.Ok;
-                    }
-                    else
+                    // If we could not add the very first entry in the enumeration, a provider must
+                    // return InsufficientBuffer.
+                    if (enumeration.IsCurrentFirst)
                     {
                         hr = HResult.InsufficientBuffer;
                     }
-
                     break;
                 }
             }
 
-            Log.Information("<---- GetDirectoryEnumerationCallback {Result}", hr);
+            if (hr == HResult.Ok)
+            {
+                Log.Information("<---- GetDirectoryEnumerationCallback {Result}", hr);
+            }
+            else
+            {
+                Log.Error("<---- GetDirectoryEnumerationCallback {Result}", hr);
+            }
             return hr;
         }