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Fix PATH caching in CommandDiscovery code #27809

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8807f50
Fix PATH caching in CommandDiscovery
daxian-dbw Aug 11, 2026
bf80646
Address feedback
daxian-dbw Aug 11, 2026
38f84f2
Minor change in comment
daxian-dbw Aug 11, 2026
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79 changes: 33 additions & 46 deletions src/System.Management.Automation/engine/CommandDiscovery.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1199,81 +1199,68 @@ internal void UnregisterLookupCommandInfoAction(string currentAction, string com
/// </remarks>
internal LookupPathCollection GetLookupDirectoryPaths()
{
LookupPathCollection result = new LookupPathCollection();

string path = Environment.GetEnvironmentVariable("PATH");
discoveryTracer.WriteLine("PATH: {0}", path);

discoveryTracer.WriteLine(
"PATH: {0}",
path);

bool isPathCacheValid =
path != null &&
string.Equals(_pathCacheKey, path, StringComparison.OrdinalIgnoreCase) &&
_cachedPath != null;
bool isPathCacheValid = _cachedLookupPaths is not null
&& string.Equals(_pathCacheKey, path, StringComparison.OrdinalIgnoreCase);

if (!isPathCacheValid)
{
// Reset the cached lookup paths
_cachedLookupPaths = null;

// Tokenize the path and cache it

_pathCacheKey = path;
_cachedLookupPaths = null;

if (_pathCacheKey != null)
if (string.IsNullOrEmpty(path))
{
// Cache an empty collection when PATH is null (unset) or an empty string.
_cachedLookupPaths = new List<string>();
}
else
{
// Tokenize the path and cache it
string[] tokenizedPath = _pathCacheKey.Split(Path.PathSeparator, StringSplitOptions.RemoveEmptyEntries);
_cachedPath = new Collection<string>();
_cachedLookupPaths = new List<string>(capacity: tokenizedPath.Length);

foreach (string directory in tokenizedPath)
{
string tempDir = directory.TrimStart();
if (tempDir.EqualsOrdinalIgnoreCase("~"))
{
tempDir = Environment.GetFolderPath(
Environment.SpecialFolder.UserProfile,
Environment.SpecialFolderOption.DoNotVerify);
}
else if (tempDir.StartsWith("~" + Path.DirectorySeparatorChar))
string tempDir = directory.Trim();
if (tempDir.StartsWith('~'))
{
tempDir = Environment.GetFolderPath(
Environment.SpecialFolder.UserProfile,
Environment.SpecialFolderOption.DoNotVerify)
+ Path.DirectorySeparatorChar
+ tempDir.Substring(2);
if (tempDir.Length is 1)
{
tempDir = Environment.GetFolderPath(
Environment.SpecialFolder.UserProfile,
Environment.SpecialFolderOption.DoNotVerify);
}
else if (tempDir[1] == Path.DirectorySeparatorChar)
{
string homeDir = Environment.GetFolderPath(
Environment.SpecialFolder.UserProfile,
Environment.SpecialFolderOption.DoNotVerify);
tempDir = $"{homeDir}{Path.DirectorySeparatorChar}{tempDir.AsSpan(2)}";
}
}

_cachedPath.Add(tempDir);
result.Add(tempDir);
_cachedLookupPaths.Add(tempDir);
}
}
}
else
{
result.AddRange(_cachedPath);
}

// Cache the new lookup paths
return _cachedLookupPaths ??= result;
// The returned instance will be mutated in 'CommandPathSearch.ResolveCurrentDirectoryInLookupPaths' when resolving relative paths,
// which depends on user's current working directory. So, we need to return a copy of the lookup paths to keep the cache intact.
return new LookupPathCollection(_cachedLookupPaths);
}

/// <summary>
/// The cached list of lookup paths. It can be invalidated by
/// the PATH changing.
/// The cached list of lookup paths. It can be invalidated by the PATH changing.
/// </summary>
private LookupPathCollection _cachedLookupPaths;
private List<string> _cachedLookupPaths;

/// <summary>
/// The key that determines if the cached PATH can be used.
/// </summary>
private string _pathCacheKey;

/// <summary>
/// The cache of the tokenized PATH directories.
/// </summary>
private Collection<string> _cachedPath;

#endregion internal members

#region environment variable helpers
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51 changes: 51 additions & 0 deletions test/powershell/Modules/Microsoft.PowerShell.Core/Get-Command.Tests.ps1
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Original file line number Diff line number Diff line change
Expand Up @@ -275,3 +275,54 @@ Describe "Get-Command Tests" -Tags "CI" {
$result | Should -Be $null
}
}

Describe "Test relative path in PATH env var" -Tags "CI" {

BeforeAll {
$originalPath = $env:PATH
$originalLocation = Get-Location

$subDir1 = Join-Path $TestDrive -ChildPath "subdir1"
$subDir2 = Join-Path $TestDrive -ChildPath "subdir2"
$toolsUnderSubDir1 = Join-Path $subDir1 -ChildPath "tools"
$toolsUnderSubDir2 = Join-Path $subDir2 -ChildPath "tools"

$null = New-Item -Path $subDir1 -ItemType Directory -Force
$null = New-Item -Path $subDir2 -ItemType Directory -Force
$null = New-Item -Path $toolsUnderSubDir1 -ItemType Directory -Force
$null = New-Item -Path $toolsUnderSubDir2 -ItemType Directory -Force

$helloScript = Join-Path $toolsUnderSubDir1 -ChildPath "hello.ps1"
$byeScript = Join-Path $toolsUnderSubDir2 -ChildPath "bye.ps1"
$null = New-Item -Path $helloScript -ItemType File -Force
$null = New-Item -Path $byeScript -ItemType File -Force
}

AfterAll {
Set-Location $originalLocation
$env:PATH = $originalPath
}

It "Get-Command should resolve relative path in PATH env var based on user's current working directory" {
$dirSep = [System.IO.Path]::DirectorySeparatorChar
$pathSep = [System.IO.Path]::PathSeparator

Set-Location $subDir1
$env:PATH = ".${dirSep}tools${pathSep}$env:PATH"

$result = Get-Command "hello.ps1" -ErrorAction silentlycontinue
$result | Should -Not -BeNullOrEmpty -Because "CWD is $subDir1, so '.${dirSep}tools' in PATH should be resolved to '$toolsUnderSubDir1', which contains 'hello.ps1'"
$result.Path | Should -BeExactly $helloScript

$result = Get-Command "bye.ps1" -ErrorAction silentlycontinue
$result | Should -BeNullOrEmpty -Because "'bye.ps1' is not in '$toolsUnderSubDir1'"

Set-Location $subDir2
$result = Get-Command "hello.ps1" -ErrorAction silentlycontinue
$result | Should -BeNullOrEmpty -Because "CWD is $subDir2, so '.${dirSep}tools' in PATH should be resolved to '$toolsUnderSubDir2', which contains 'bye.ps1'"

$result = Get-Command "bye.ps1" -ErrorAction silentlycontinue
$result | Should -Not -BeNullOrEmpty
$result.Path | Should -BeExactly $byeScript
}
}
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