Port #29413 to release branch

Enumerating strings should retain trailing separators
(#29413)

This is a regression introduced by the enumeration overhaul. We didn't have tests that covered trailing separators in the specified root directory when enumerating. They should be retained as is.

4 files changed, 53 insertions, 0 deletions

diff --git a/src/System.IO.FileSystem/tests/Directory/GetFiles.cs b/src/System.IO.FileSystem/tests/Directory/GetFiles.cs
index 79c22762df..7a8a36bde6 100644
--- a/src/System.IO.FileSystem/tests/Directory/GetFiles.cs
+++ b/src/System.IO.FileSystem/tests/Directory/GetFiles.cs
@@ -147,6 +147,8 @@ namespace System.IO.Tests
 
     public class Directory_GetFiles_str_str_so : Directory_GetFileSystemEntries_str_str_so
     {
+        public virtual bool IsDirectoryInfo => false;
+
         protected override bool TestFiles { get { return true; } }
         protected override bool TestDirectories { get { return false; } }
 
@@ -164,5 +166,32 @@ namespace System.IO.Tests
         {
             return Directory.GetFiles(path, searchPattern, option);
         }
+
+        [Theory, MemberData(nameof(TrailingSeparators))]
+        public void DirectoryWithTrailingSeparators(string trailing)
+        {
+            // When getting strings back we should retain the root path as specified for Directory.
+            // DirectoryInfo returns the normalized full path in all cases.
+
+            // Add the trailing separator up front for Directory as we want to validate against
+            // the path _with_ the separator on it. Creation doesn't care about trailing, and
+            // Path.Combine doesn't change the existing separators, it just adds the canonical
+            // separator if needed.
+            string root = GetTestFilePath() + (IsDirectoryInfo ? "" : trailing);
+            string rootFile = Path.Combine(root, GetTestFileName());
+            string subDirectory = Path.Combine(root, GetTestFileName());
+            string nestedFile = Path.Combine(subDirectory, GetTestFileName());
+
+            Directory.CreateDirectory(subDirectory);
+            File.Create(rootFile).Dispose();
+            File.Create(nestedFile).Dispose();
+
+            // Add the trailing separator if we haven't (for DI) so we can validate that we
+            // either retain (D) or don't retain (DI) the separators as we specified them.
+            // Note that some of the cases actually match canonical (one standard separator)
+            // so they never change.
+            string[] files = GetEntries(root + (IsDirectoryInfo ? trailing : ""), "*", SearchOption.AllDirectories);
+            FSAssert.EqualWhenOrdered(new string[] { rootFile, nestedFile }, files);
+        }
     }
 }
diff --git a/src/System.IO.FileSystem/tests/DirectoryInfo/EnumerableAPIs.cs b/src/System.IO.FileSystem/tests/DirectoryInfo/EnumerableAPIs.cs
index 8be99d828c..dd1875a2d5 100644
--- a/src/System.IO.FileSystem/tests/DirectoryInfo/EnumerableAPIs.cs
+++ b/src/System.IO.FileSystem/tests/DirectoryInfo/EnumerableAPIs.cs
@@ -32,6 +32,8 @@ namespace System.IO.Tests
 
     public class DirectoryInfo_EnumerateFiles_str_str_so : Directory_GetFiles_str_str_so
     {
+        public override bool IsDirectoryInfo => true;
+
         public override string[] GetEntries(string path)
         {
             return ((new DirectoryInfo(path).EnumerateFiles("*", SearchOption.TopDirectoryOnly).Select(x => x.FullName)).ToArray());
diff --git a/src/System.IO.FileSystem/tests/DirectoryInfo/GetFiles.cs b/src/System.IO.FileSystem/tests/DirectoryInfo/GetFiles.cs
index 85fef80609..13970ae34d 100644
--- a/src/System.IO.FileSystem/tests/DirectoryInfo/GetFiles.cs
+++ b/src/System.IO.FileSystem/tests/DirectoryInfo/GetFiles.cs
@@ -30,6 +30,8 @@ namespace System.IO.Tests
 
     public class DirectoryInfo_GetFiles_str_so : Directory_GetFiles_str_str_so
     {
+        public override bool IsDirectoryInfo => true;
+
         public override string[] GetEntries(string path)
         {
             return ((new DirectoryInfo(path).GetFiles("*", SearchOption.TopDirectoryOnly).Select(x => x.FullName)).ToArray());
diff --git a/src/System.IO.FileSystem/tests/FileSystemTest.cs b/src/System.IO.FileSystem/tests/FileSystemTest.cs
index 6f020a00f6..ff21035632 100644
--- a/src/System.IO.FileSystem/tests/FileSystemTest.cs
+++ b/src/System.IO.FileSystem/tests/FileSystemTest.cs
@@ -33,6 +33,26 @@ namespace System.IO.Tests
         public static TheoryData ControlWhiteSpace = IOInputs.GetControlWhiteSpace().ToTheoryData();
         public static TheoryData NonControlWhiteSpace = IOInputs.GetNonControlWhiteSpace().ToTheoryData();
 
+        public static TheoryData<string> TrailingSeparators
+        {
+            get
+            {
+                var data = new TheoryData<string>()
+                {
+                    "",
+                    "" + Path.DirectorySeparatorChar,
+                    "" + Path.DirectorySeparatorChar + Path.DirectorySeparatorChar
+                };
+
+                if (PlatformDetection.IsWindows)
+                {
+                    data.Add("" + Path.AltDirectorySeparatorChar);
+                }
+
+                return data;
+            }
+        }
+
         /// <summary>
         /// In some cases (such as when running without elevated privileges),
         /// the symbolic link may fail to create. Only run this test if it creates