Make final API review changes to file enumeration (#27318)

* Make final API review changes to file enumeration

Tweak stack array initialization to just zero the first element in matcher algorithm.

cc: @danmosemsft @terrajobst

* Don't null out the native name to track conversion

11 files changed, 57 insertions, 25 deletions

diff --git a/src/System.IO.FileSystem/ref/System.IO.FileSystem.cs b/src/System.IO.FileSystem/ref/System.IO.FileSystem.cs
index cd19c96ab5..8f0ee01b28 100644
--- a/src/System.IO.FileSystem/ref/System.IO.FileSystem.cs
+++ b/src/System.IO.FileSystem/ref/System.IO.FileSystem.cs
@@ -226,7 +226,7 @@ namespace System.IO
     public enum MatchType
     {
         Simple,
-        Dos
+        Win32
     }
     public enum MatchCasing
     {
@@ -260,6 +260,7 @@ namespace System.IO.Enumeration
         public DateTimeOffset LastAccessTimeUtc { get { throw null; } }
         public DateTimeOffset LastWriteTimeUtc { get { throw null; } }
         public bool IsDirectory { get { throw null; } }
+        public bool IsHidden { get { throw null; } }
         public FileSystemInfo ToFileSystemInfo() { throw null; }
         public string ToSpecifiedFullPath() { throw null; }
         public string ToFullPath() { throw null; }
@@ -297,8 +298,8 @@ namespace System.IO.Enumeration
     }
     public static class FileSystemName
     {
-        public static string TranslateDosExpression(string expression) { throw null; }
-        public static bool MatchesDosExpression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true) { throw null; }
+        public static string TranslateWin32Expression(string expression) { throw null; }
+        public static bool MatchesWin32Expression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true) { throw null; }
         public static bool MatchesSimpleExpression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true) { throw null; }
     }
 }
diff --git a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Unix.cs b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Unix.cs
index f5339377b3..eb0bc1e68d 100644
--- a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Unix.cs
+++ b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Unix.cs
@@ -88,14 +88,13 @@ namespace System.IO.Enumeration
         {
             get
             {
-                if (_directoryEntry.Name != null)
+                if (_directoryEntry.NameLength != 0 && _fileName.Length == 0)
                 {
                     fixed (char* c = _fileNameBuffer)
                     {
                         Span<char> buffer = new Span<char>(c, FileNameBufferSize);
                         _fileName = _directoryEntry.GetName(buffer);
                     }
-                    _directoryEntry.Name = null;
                 }
 
                 return _fileName;
@@ -129,6 +128,7 @@ namespace System.IO.Enumeration
         public DateTimeOffset LastAccessTimeUtc => _status.GetLastAccessTime(FullPath, continueOnError: true);
         public DateTimeOffset LastWriteTimeUtc => _status.GetLastWriteTime(FullPath, continueOnError: true);
         public bool IsDirectory => _status.InitiallyDirectory;
+        public bool IsHidden => _directoryEntry.Name[0] == '.';
 
         public FileSystemInfo ToFileSystemInfo()
         {
diff --git a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Windows.cs b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Windows.cs
index c7bedb181c..f3bdd4a852 100644
--- a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Windows.cs
+++ b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEntry.Windows.cs
@@ -67,6 +67,11 @@ namespace System.IO.Enumeration
         /// </summary>
         public bool IsDirectory => (Attributes & FileAttributes.Directory) != 0;
 
+        /// <summary>
+        /// Returns true if the file has the hidden attribute.
+        /// </summary>
+        public bool IsHidden => (Attributes & FileAttributes.Hidden) != 0;
+
         public FileSystemInfo ToFileSystemInfo()
             => FileSystemInfo.Create(PathHelpers.CombineNoChecks(Directory, FileName), ref this);
 
diff --git a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEnumerableFactory.cs b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEnumerableFactory.cs
index 84e67fbffb..b8eae46ad3 100644
--- a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEnumerableFactory.cs
+++ b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemEnumerableFactory.cs
@@ -37,7 +37,7 @@ namespace System.IO.Enumeration
 
             switch (options.MatchType)
             {
-                case MatchType.Dos:
+                case MatchType.Win32:
                     if (string.IsNullOrEmpty(expression) || expression == "." || expression == "*.*")
                     {
                         // Historically we always treated "." as "*"
@@ -57,7 +57,7 @@ namespace System.IO.Enumeration
                         }
 
                         // Need to convert the expression to match Win32 behavior
-                        expression = FileSystemName.TranslateDosExpression(expression);
+                        expression = FileSystemName.TranslateWin32Expression(expression);
                     }
                     break;
                 case MatchType.Simple:
@@ -76,8 +76,8 @@ namespace System.IO.Enumeration
             {
                 case MatchType.Simple:
                     return FileSystemName.MatchesSimpleExpression(expression, name, ignoreCase);
-                case MatchType.Dos:
-                    return FileSystemName.MatchesDosExpression(expression, name, ignoreCase);
+                case MatchType.Win32:
+                    return FileSystemName.MatchesWin32Expression(expression, name, ignoreCase);
                 default:
                     throw new ArgumentOutOfRangeException(nameof(options));
             }
diff --git a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemName.cs b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemName.cs
index 10ef61cf83..2de8d2a4ad 100644
--- a/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemName.cs
+++ b/src/System.IO.FileSystem/src/System/IO/Enumeration/FileSystemName.cs
@@ -28,7 +28,7 @@ namespace System.IO.Enumeration
         /// Change '*' and '?' to '&lt;', '&gt;' and '"' to match Win32 behavior. For compatibility, Windows
         /// changes some wildcards to provide a closer match to historical DOS 8.3 filename matching.
         /// </summary>
-        public static string TranslateDosExpression(string expression)
+        public static string TranslateWin32Expression(string expression)
         {
             if (string.IsNullOrEmpty(expression) || expression == "*" || expression == "*.*")
                 return "*";
@@ -82,9 +82,9 @@ namespace System.IO.Enumeration
         /// of RtlIsNameInExpression, which defines the rules for matching DOS wildcards ('*', '?', '&lt;', '&gt;', '"').
         /// 
         /// Like PatternMatcher, matching will not line up with Win32 behavior unless you transform the expression
-        /// using <see cref="TranslateDosExpression(string)"/>
+        /// using <see cref="TranslateWin32Expression(string)"/>
         /// </remarks>
-        public static bool MatchesDosExpression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true)
+        public static bool MatchesWin32Expression(ReadOnlySpan<char> expression, ReadOnlySpan<char> name, bool ignoreCase = true)
         {
             return MatchPattern(expression, name, ignoreCase, useExtendedWildcards: true);
         }
@@ -141,7 +141,7 @@ namespace System.IO.Enumeration
             Span<int> temp = stackalloc int[0];
             Span<int> currentMatches = stackalloc int[16];
             Span<int> priorMatches = stackalloc int[16];
-            priorMatches.Clear();
+            priorMatches[0] = 0;
 
             int maxState = expression.Length * 2;
             int currentState;
diff --git a/src/System.IO.FileSystem/src/System/IO/EnumerationOptions.cs b/src/System.IO.FileSystem/src/System/IO/EnumerationOptions.cs
index 3659ee7472..d78e8368e3 100644
--- a/src/System.IO.FileSystem/src/System/IO/EnumerationOptions.cs
+++ b/src/System.IO.FileSystem/src/System/IO/EnumerationOptions.cs
@@ -11,10 +11,10 @@ namespace System.IO
         /// explicitly specify EnumerationOptions.
         /// </summary>
         internal static EnumerationOptions Compatible { get; } = new EnumerationOptions
-            { MatchType = MatchType.Dos, AttributesToSkip = 0, IgnoreInaccessible = false };
+            { MatchType = MatchType.Win32, AttributesToSkip = 0, IgnoreInaccessible = false };
 
         private static EnumerationOptions CompatibleRecursive { get; } = new EnumerationOptions
-            { RecurseSubdirectories = true, MatchType = MatchType.Dos, AttributesToSkip = 0, IgnoreInaccessible = false };
+            { RecurseSubdirectories = true, MatchType = MatchType.Win32, AttributesToSkip = 0, IgnoreInaccessible = false };
 
         /// <summary>
         /// Internal singleton for default options.
diff --git a/src/System.IO.FileSystem/src/System/IO/MatchType.cs b/src/System.IO.FileSystem/src/System/IO/MatchType.cs
index 9789390d95..0bdf89b3c7 100644
--- a/src/System.IO.FileSystem/src/System/IO/MatchType.cs
+++ b/src/System.IO.FileSystem/src/System/IO/MatchType.cs
@@ -12,9 +12,9 @@ namespace System.IO
         Simple,
 
         /// <summary>
-        /// Match using DOS style matching semantics. '*', '?', '&lt;', '&gt;', and '"'
+        /// Match using Win32 DOS style matching semantics. '*', '?', '&lt;', '&gt;', and '"'
         /// are all considered wildcards.
         /// </summary>
-        Dos
+        Win32
     }
 }
diff --git a/src/System.IO.FileSystem/tests/Enumeration/AttributeTests.netcoreapp.cs b/src/System.IO.FileSystem/tests/Enumeration/AttributeTests.netcoreapp.cs
index d35783713f..2ba62dfb42 100644
--- a/src/System.IO.FileSystem/tests/Enumeration/AttributeTests.netcoreapp.cs
+++ b/src/System.IO.FileSystem/tests/Enumeration/AttributeTests.netcoreapp.cs
@@ -2,6 +2,7 @@
 // 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.Collections.Generic;
 using System.IO.Enumeration;
 using Xunit;
 
@@ -111,5 +112,30 @@ namespace System.IO.Tests.Enumeration
                 Assert.False(enumerator.MoveNext());
             }
         }
+
+        [Fact]
+        public void IsHiddenAttribute()
+        {
+            DirectoryInfo testDirectory = Directory.CreateDirectory(GetTestFilePath());
+            FileInfo fileOne = new FileInfo(Path.Combine(testDirectory.FullName, GetTestFileName()));
+
+            // Put a period in front to make it hidden on Unix
+            FileInfo fileTwo = new FileInfo(Path.Combine(testDirectory.FullName, "." + GetTestFileName()));
+
+            fileOne.Create().Dispose();
+            fileTwo.Create().Dispose();
+            if (PlatformDetection.IsWindows)
+                fileTwo.Attributes = fileTwo.Attributes | FileAttributes.Hidden;
+
+            IEnumerable<string> enumerable = new FileSystemEnumerable<string>(
+                testDirectory.FullName,
+                (ref FileSystemEntry entry) => entry.ToFullPath(),
+                new EnumerationOptions() { AttributesToSkip = 0 })
+            {
+                ShouldIncludePredicate = (ref FileSystemEntry entry) => entry.IsHidden
+            };
+
+            Assert.Equal(new string[] { fileTwo.FullName }, enumerable);
+        }
     }
 }
diff --git a/src/System.IO.FileSystem/tests/Enumeration/PatternTransformTests.netcoreapp.cs b/src/System.IO.FileSystem/tests/Enumeration/PatternTransformTests.netcoreapp.cs
index d9e8b5330d..9cb33e5853 100644
--- a/src/System.IO.FileSystem/tests/Enumeration/PatternTransformTests.netcoreapp.cs
+++ b/src/System.IO.FileSystem/tests/Enumeration/PatternTransformTests.netcoreapp.cs
@@ -32,7 +32,7 @@ namespace System.IO.Tests.Enumeration
             string[] results = GetFiles(testDirectory.FullName, pattern);
             FSAssert.EqualWhenOrdered(new string[] { fileOne.FullName, fileTwo.FullName }, results);
 
-            results = GetFiles(testDirectory.FullName, pattern, new EnumerationOptions { MatchType = MatchType.Dos });
+            results = GetFiles(testDirectory.FullName, pattern, new EnumerationOptions { MatchType = MatchType.Win32 });
             FSAssert.EqualWhenOrdered(new string[] { fileOne.FullName, fileTwo.FullName }, results);
         }
 
diff --git a/src/System.IO.FileSystem/tests/Enumeration/DosMatcherTests.netcoreapp.cs b/src/System.IO.FileSystem/tests/Enumeration/Win32MatcherTests.netcoreapp.cs
index 508f0f6bf9..bc1d529969 100644
--- a/src/System.IO.FileSystem/tests/Enumeration/DosMatcherTests.netcoreapp.cs
+++ b/src/System.IO.FileSystem/tests/Enumeration/Win32MatcherTests.netcoreapp.cs
@@ -7,15 +7,15 @@ using Xunit;
 
 namespace System.IO.Tests
 {
-    public class DosMatcherTests
+    public class Win32MatcherTests
     {
-        [Theory, MemberData(nameof(DosMatchData)), MemberData(nameof(EscapedDosMatchData))]
-        public static void DosMatch(string expression, string name, bool ignoreCase, bool expected)
+        [Theory, MemberData(nameof(Win32MatchData)), MemberData(nameof(EscapedWin32MatchData))]
+        public static void Win32Match(string expression, string name, bool ignoreCase, bool expected)
         {
-            Assert.Equal(expected, FileSystemName.MatchesDosExpression(expression, name.AsSpan(), ignoreCase));
+            Assert.Equal(expected, FileSystemName.MatchesWin32Expression(expression, name.AsSpan(), ignoreCase));
         }
 
-        public static TheoryData<string, string, bool, bool> EscapedDosMatchData => new TheoryData<string, string, bool, bool>
+        public static TheoryData<string, string, bool, bool> EscapedWin32MatchData => new TheoryData<string, string, bool, bool>
         {
             // Trailing escape matches as it is considered "invisible"
             { "\\", "\\", false, true },
@@ -43,7 +43,7 @@ namespace System.IO.Tests
             { "\\\"", "\"", true, true },
         };
 
-        public static TheoryData<string, string, bool, bool> DosMatchData => new TheoryData<string, string, bool, bool>
+        public static TheoryData<string, string, bool, bool> Win32MatchData => new TheoryData<string, string, bool, bool>
         {
             { null, "", false, false },
             { null, "", true, false },
diff --git a/src/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj b/src/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj
index 672d5642dc..5ff308577c 100644
--- a/src/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj
+++ b/src/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj
@@ -56,7 +56,7 @@
     <Compile Include="Enumeration\ConstructionTests.netcoreapp.cs" />
     <Compile Include="Enumeration\SpecialDirectoryTests.netcoreapp.cs" />
     <Compile Include="Enumeration\SkipAttributeTests.netcoreapp.cs" />
-    <Compile Include="Enumeration\DosMatcherTests.netcoreapp.cs" />
+    <Compile Include="Enumeration\Win32MatcherTests.netcoreapp.cs" />
     <Compile Include="Enumeration\MatchCasingTests.netcoreapp.cs" />
     <Compile Include="Enumeration\TrimmedPaths.netcoreapp.cs" />
     <Compile Include="Enumeration\ErrorHandlingTests.netcoreapp.cs" />