Simplify Extension parameter handling and add edge case tests

yotsuda · yotsuda · commit 9b084f260f5c · 2025-11-21T09:44:03.000+09:00
- Simplify extension logic: use ternary operator to pass null when empty
- Remove TrimEnd('.'): fixes issue where dots in base name were removed
- Add test cases for preserving dots in base name:
  * When removing extension (file...txt -&gt; file..)
  * When changing extension (file...txt -&gt; file...md)
diff --git a/src/Microsoft.PowerShell.Commands.Management/commands/management/CombinePathCommand.cs b/src/Microsoft.PowerShell.Commands.Management/commands/management/CombinePathCommand.cs
@@ -144,13 +144,7 @@ protected override void ProcessRecord()
                 // Change extension if specified
                 if (Extension != null && joinedPath != null)
                 {
-                    joinedPath = System.IO.Path.ChangeExtension(joinedPath, Extension);
-
-                    // Remove trailing dot when extension is empty string
-                    if (Extension.Length == 0)
-                    {
-                        joinedPath = joinedPath.TrimEnd('.');
-                    }
+                    joinedPath = System.IO.Path.ChangeExtension(joinedPath, Extension.Length == 0 ? null : Extension);
                 }
 
                 if (Resolve)
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Management/Join-Path.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Management/Join-Path.Tests.ps1
@@ -96,6 +96,10 @@ Describe "Join-Path cmdlet tests" -Tags "CI" {
     $result = Join-Path -Path "folder" -ChildPath "file.txt" -Extension ""
     $result | Should -BeExactly "folder${SepChar}file"
   }
+  It "should preserve dots in base name when removing extension with empty string" {
+    $result = Join-Path -Path "folder" -ChildPath "file...txt" -Extension ""
+    $result | Should -BeExactly "folder${SepChar}file.."
+  }
   It "should change extension for multiple paths" {
     $result = Join-Path -Path "folder1", "folder2" -ChildPath "file.txt" -Extension ".log"
     $result.Count | Should -Be 2
@@ -112,6 +116,10 @@ Describe "Join-Path cmdlet tests" -Tags "CI" {
     $result = Join-Path -Path "folder" -ChildPath "file.backup.txt" -Extension ".log"
     $result | Should -BeExactly "folder${SepChar}file.backup.log"
   }
+  It "should preserve dots in base name when changing extension" {
+    $result = Join-Path -Path "folder" -ChildPath "file...txt" -Extension ".md"
+    $result | Should -BeExactly "folder${SepChar}file...md"
+  }
   It "should add extension to directory-like path" {
     $result = Join-Path -Path "folder" -ChildPath "subfolder" -Extension ".log"
     $result | Should -BeExactly "folder${SepChar}subfolder.log"

Original file line number	Diff line number	Diff line change
`@@ -144,13 +144,7 @@ protected override void ProcessRecord()`
`144`	`144`	`// Change extension if specified`
`145`	`145`	`if (Extension != null && joinedPath != null)`
`146`	`146`	`{`
`147`		`- joinedPath = System.IO.Path.ChangeExtension(joinedPath, Extension);`
`148`		`-`
`149`		`- // Remove trailing dot when extension is empty string`
`150`		`- if (Extension.Length == 0)`
`151`		`- {`
`152`		`- joinedPath = joinedPath.TrimEnd('.');`
`153`		`- }`
	`147`	`+ joinedPath = System.IO.Path.ChangeExtension(joinedPath, Extension.Length == 0 ? null : Extension);`
`154`	`148`	`}`
`155`	`149`
`156`	`150`	`if (Resolve)`