🐛 Workaround .NET bug

The [Environment]::SetEnvironmentVariable() method is completely
broken for any expandable values.
See https://github.com/dotnet/corefx/issues/36449 - the issue is still
not resolved even in current versions of .NET Core. The only safe
method to set PATH and other values requiring expandable string
typing in the registry is via the registry APIs.

Uninstallation.md

@@ -57,13 +57,11 @@ if (-not (Test-Path $env:ChocolateyInstall)) {
     accidentally overwrite them with absolute path values. Where the registry allows us to see "%SystemRoot%" in a PATH
     entry, PowerShell's registry provider only sees "C:\Windows", for example.
 #>
-$userPath = [Microsoft.Win32.Registry]::CurrentUser.OpenSubKey(
-    'Environment'
-).GetValue('PATH', [string]::Empty, 'DoNotExpandEnvironmentNames').ToString()
+$userKey = [Microsoft.Win32.Registry]::CurrentUser.OpenSubKey('Environment')
+$userPath = $userKey.GetValue('PATH', [string]::Empty, 'DoNotExpandEnvironmentNames').ToString()
 
-$machinePath = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey(
-    'SYSTEM\CurrentControlSet\Control\Session Manager\Environment\'
-).GetValue('PATH', [string]::Empty, 'DoNotExpandEnvironmentNames').ToString()
+$machineKey = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey('SYSTEM\ControlSet001\Control\Session Manager\Environment\')
+$machinePath = $machineKey.GetValue('PATH', [string]::Empty, 'DoNotExpandEnvironmentNames').ToString()
 
 $backupPATHs = @(
     "User PATH: $userPath"
@@ -86,7 +84,9 @@ if ($userPath -like "*$env:ChocolateyInstall*") {
             Where-Object { $_ -and $_ -ne "$env:ChocolateyInstall\bin" }
     ) -join [System.IO.Path]::PathSeparator
 
-    [Environment]::SetEnvironmentVariable('PATH', $newUserPATH, 'User')
+    # NEVER use [Environment]::SetEnvironmentVariable() for PATH values; see https://github.com/dotnet/corefx/issues/36449
+    # This issue exists in ALL released versions of .NET and .NET Core as of 12/19/2019
+    $userKey.SetValue('PATH', $newUserPATH, 'ExpandString')
 }
 
 if ($machinePath -like "*$env:ChocolateyInstall*") {
@@ -98,7 +98,9 @@ if ($machinePath -like "*$env:ChocolateyInstall*") {
             Where-Object { $_ -and $_ -ne "$env:ChocolateyInstall\bin" }
     ) -join [System.IO.Path]::PathSeparator
 
-    [Environment]::SetEnvironmentVariable('PATH', $newMachinePATH, 'Machine')
+    # NEVER use [Environment]::SetEnvironmentVariable() for PATH values; see https://github.com/dotnet/corefx/issues/36449
+    # This issue exists in ALL released versions of .NET and .NET Core as of 12/19/2019
+    $machineKey.SetValue('PATH', $newMachinePATH, 'ExpandString')
 }
 
 # Adapt for any services running in subfolders of ChocolateyInstall
@@ -115,6 +117,9 @@ Remove-Item -Path $env:ChocolateyInstall -Recurse -Force -WhatIf
         [Environment]::SetEnvironmentVariable($_, [string]::Empty, $scope)
     }
 }
+
+$machineKey.Close()
+$userKey.Close()
 ~~~
 
 Additionally, the below code will remove the environment variables pointing to the tools directory that was managed by Chocolatey.