From b18eacaa831cef05bd97ef2ae557cab4eabd5e9e Mon Sep 17 00:00:00 2001
From: Matej Kafka <6414091+MatejKafka@users.noreply.github.com>
Date: Wed, 4 Dec 2024 00:00:00 +0100
Subject: [PATCH] Resolve symbolic link target relative to the symbolic link
 instead of the working directory (#15235) (#20943)

---
 .../namespaces/FileSystemProvider.cs          | 16 ++++-----
 .../FileSystem.Tests.ps1                      | 33 +++++++++++++++++++
 2 files changed, 40 insertions(+), 9 deletions(-)

diff --git a/src/System.Management.Automation/namespaces/FileSystemProvider.cs b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
index d22fcdc88f..d23c8ebead 100644
--- a/src/System.Management.Automation/namespaces/FileSystemProvider.cs
+++ b/src/System.Management.Automation/namespaces/FileSystemProvider.cs
@@ -2258,16 +2258,14 @@ namespace Microsoft.PowerShell.Commands
                         {
                             exists = true;
 
-                            var normalizedTargetPath = strTargetPath;
-                            if (strTargetPath.StartsWith(".\\", StringComparison.OrdinalIgnoreCase) ||
-                                strTargetPath.StartsWith("./", StringComparison.OrdinalIgnoreCase))
-                            {
-                                normalizedTargetPath = Path.Join(SessionState.Internal.CurrentLocation.ProviderPath, strTargetPath.AsSpan(2));
-                            }
-
-                            GetFileSystemInfo(normalizedTargetPath, out isDirectory);
-
+                            // unify directory separators to be consistent with the rest of PowerShell even on non-Windows platforms;
+                            // do this before resolving the target, otherwise e.g. `.\test` would break on Linux, since the combined
+                            // path below would be something like `/path/to/cwd/.\test`
                             strTargetPath = strTargetPath.Replace(StringLiterals.AlternatePathSeparator, StringLiterals.DefaultPathSeparator);
+
+                            // check if the target is a file or directory
+                            var normalizedTargetPath = Path.Combine(Path.GetDirectoryName(path), strTargetPath);
+                            GetFileSystemInfo(normalizedTargetPath, out isDirectory);
                         }
                         else
                         {
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1
index b43d7033ca..b365862f9d 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Management/FileSystem.Tests.ps1
@@ -1,5 +1,8 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
+
+Import-Module HelpersCommon
+
 Describe "Basic FileSystem Provider Tests" -Tags "CI" {
     BeforeAll {
         $testDir = "TestDir"
@@ -621,6 +624,11 @@ Describe "Hard link and symbolic link tests" -Tags "CI", "RequireAdminOnWindows"
     }
 
     Context "New-Item and hard/symbolic links" {
+        AfterEach {
+            # clean up created links after each test
+            Remove-Item -Exclude (Split-Path -Leaf $realFile, $realDir, $realDir2) -Recurse $TestPath/*
+        }
+
         It "New-Item can create a hard link to a file" {
             New-Item -ItemType HardLink -Path $hardLinkToFile -Value $realFile > $null
             Test-Path $hardLinkToFile | Should -BeTrue
@@ -664,6 +672,31 @@ Describe "Hard link and symbolic link tests" -Tags "CI", "RequireAdminOnWindows"
             $link.LinkType | Should -BeExactly "SymbolicLink"
             $link.Target | Should -BeExactly $real.ToString()
         }
+
+        It "New-Item can create a directory symbolic link to a directory using a relative path" -Skip:(-Not $IsWindows) {
+            $target = Split-Path -Leaf $realDir
+            New-Item -ItemType SymbolicLink -Path $symLinkToDir -Value $target > $null
+            Test-Path $symLinkToDir | Should -BeTrue
+            $real = Get-Item -Path $realDir
+            $link = Get-Item -Path $symLinkToDir
+            $link | Should -BeOfType System.IO.DirectoryInfo
+            $link.LinkType | Should -BeExactly "SymbolicLink"
+            $link.ResolvedTarget | Should -BeExactly $real.ToString()
+            $link.Target | Should -BeExactly $target
+        }
+
+        It "New-Item can create a directory symbolic link to a directory using a relative path with .\" -Skip:(-Not $IsWindows) {
+            $target = ".\$(Split-Path -Leaf $realDir)"
+            New-Item -ItemType SymbolicLink -Path $symLinkToDir -Value $target > $null
+            Test-Path $symLinkToDir | Should -BeTrue
+            $real = Get-Item -Path $realDir
+            $link = Get-Item -Path $symLinkToDir
+            $link | Should -BeOfType System.IO.DirectoryInfo
+            $link.LinkType | Should -BeExactly "SymbolicLink"
+            $link.ResolvedTarget | Should -BeExactly $real.ToString()
+            $link.Target | Should -BeExactly $target
+        }
+
         It "New-Item can create a directory junction to a directory" -Skip:(-Not $IsWindows) {
             New-Item -ItemType Junction -Path $junctionToDir -Value $realDir > $null
             Test-Path $junctionToDir | Should -BeTrue