From 21de8d3f8a4dc2929e9b11b05934b3e408cea42e Mon Sep 17 00:00:00 2001
From: MartinGC94 <MGC94@outlook.dk>
Date: Sun, 27 Apr 2025 13:47:24 +0200
Subject: [PATCH] Revert "Allow empty prefix string in 'Import-Module -Prefix'
 to override default prefix in manifest (#20409)"

This reverts commit b8ed5be26d0a477e5061a216223ac0edd8eedb95.
---
 .../engine/Modules/ModuleCmdletBase.cs               | 12 +++++++++++-
 .../Import-Module.Tests.ps1                          | 12 ------------
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/src/System.Management.Automation/engine/Modules/ModuleCmdletBase.cs b/src/System.Management.Automation/engine/Modules/ModuleCmdletBase.cs
index 105704fb256..f47f9b45e48 100644
--- a/src/System.Management.Automation/engine/Modules/ModuleCmdletBase.cs
+++ b/src/System.Management.Automation/engine/Modules/ModuleCmdletBase.cs
@@ -1620,7 +1620,17 @@ internal PSModuleInfo LoadModuleManifest(
                 if (bailOnFirstError) return null;
             }
 
-            string resolvedCommandPrefix = BasePrefix ?? defaultCommandPrefix ?? string.Empty;
+            string resolvedCommandPrefix = string.Empty;
+
+            if (!string.IsNullOrEmpty(defaultCommandPrefix))
+            {
+                resolvedCommandPrefix = defaultCommandPrefix;
+            }
+
+            if (!string.IsNullOrEmpty(this.BasePrefix))
+            {
+                resolvedCommandPrefix = this.BasePrefix;
+            }
 
             if (!string.IsNullOrEmpty(actualRootModule))
             {
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Core/Import-Module.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Core/Import-Module.Tests.ps1
index 2cc21dc03f3..6885abe847d 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Core/Import-Module.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Core/Import-Module.Tests.ps1
@@ -57,18 +57,6 @@ Describe "Import-Module" -Tags "CI" {
         (Get-Module TestModule).Version | Should -BeIn "1.1"
     }
 
-
-    It 'Should override default command prefix if an empty string is provided' {
-        $ModuleName = "PrefixTestModule"
-        $ModulePath = Join-Path -Path $testdrive -ChildPath $ModuleName
-        $null = New-Item -Path $ModulePath -ItemType Directory -Force
-        'function Use-Something{}' | Set-Content -Path "$ModulePath\$ModuleName.psm1" -Force
-        New-ModuleManifest -Path "$ModulePath\$ModuleName.psd1" -DefaultCommandPrefix MyPrefix -FunctionsToExport Use-Something -RootModule "$ModuleName.psm1"
-        $ImportedModule = Import-Module -Name "$ModulePath\$ModuleName.psd1" -Prefix "" -PassThru
-        $ImportedModule.ExportedCommands.ContainsKey('Use-Something') | Should -Be $true
-        Remove-Module -ModuleInfo $ImportedModule
-    }
-
     It 'ProcessorArchitecture should work' {
         $currentProcessorArchitecture = switch ([System.Runtime.InteropServices.RuntimeInformation]::ProcessArchitecture) {
             'X86' { 'x86' }