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Refactor character validation to use char.IsAsciiLetter #26270

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Refactor character validation to use char.IsAsciiLetter #26270

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12 changes: 4 additions & 8 deletions src/System.Management.Automation/engine/SessionStateDriveAPIs.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -877,8 +877,6 @@ private bool ValidateOrRemoveAutoMountedDrive(PSDriveInfo drive, SessionStateSco
/// <returns>Absence of mounted drive for FileSystem provider or False for other provider types.</returns>
private bool IsAStaleVhdMountedDrive(PSDriveInfo drive)
{
bool result = false;

// check that drive's provider type is FileSystem
if ((drive.Provider != null) && (!drive.Provider.NameEquals(this.ExecutionContext.ProviderNames.FileSystem)))
{
Expand All @@ -894,21 +892,19 @@ private bool IsAStaleVhdMountedDrive(PSDriveInfo drive)
// 3. Unmount the VHD in session 'A'.
// The drive pointing to VHD in session 'B' gets detected as DriveType.NoRootDirectory
// after the VHD is removed in session 'A'.
if (drive != null && !string.IsNullOrEmpty(drive.Name) && drive.Name.Length == 1)
if (drive is { Name.Length: 1 })
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@iSazonov iSazonov Oct 22, 2025

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I'd prefer to avoid using patterns since we haven't nullability check enabled.
I guess something classic like drive?.Name?.Length == 1 would work here.

{
try
{
char driveChar = Convert.ToChar(drive.Name, CultureInfo.InvariantCulture);

if (char.ToUpperInvariant(driveChar) >= 'A' && char.ToUpperInvariant(driveChar) <= 'Z')
if (char.IsAsciiLetter(drive.Name[0]))
{
DriveInfo systemDriveInfo = new DriveInfo(drive.Name);

if (systemDriveInfo.DriveType == DriveType.NoRootDirectory)
{
if (!Directory.Exists(drive.Root))
{
result = true;
return true;
}
}
}
Expand All @@ -919,7 +915,7 @@ private bool IsAStaleVhdMountedDrive(PSDriveInfo drive)
}
}

return result;
return false;
}

/// <summary>
Expand Down
13 changes: 8 additions & 5 deletions src/System.Management.Automation/engine/runtime/CompiledScriptBlock.cs
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Expand Up @@ -2023,11 +2023,14 @@ public static string Match(string text)
for (int i = 0; i < text.Length; i++)
{
uint h = text[i];
if (h >= 'A' && h <= 'Z')
if (h == '-')
{
}
else if (char.IsAsciiLetter((char)h))
{
h |= 0x20; // ToLower
}
else if (!((h >= 'a' && h <= 'z') || h == '-'))
else
{
// If the character isn't in any of our patterns,
// don't bother hashing and reset the running length.
Expand Down Expand Up @@ -2070,11 +2073,11 @@ public static string Match(string text)
// This code can be used when adding a new pattern.
internal static uint HashNewPattern(string pattern)
{
char ToLower(char c)
uint ToLower(uint c)
{
if (c >= 'A' && c <= 'Z')
if (char.IsAsciiLetterUpper((char)c))
{
c = (char) (c | 0x20);
c |= 0x20;
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@iSazonov iSazonov Oct 22, 2025 •
edited
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Please don't change non-compiled code.

}

return c;
Expand Down
13 changes: 1 addition & 12 deletions src/System.Management.Automation/namespaces/FileSystemProvider.cs
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Expand Up @@ -732,18 +732,7 @@ protected override PSDriveInfo RemoveDrive(PSDriveInfo drive)
/// <returns>True if the drive can be persisted or else false.</returns>
private static bool IsSupportedDriveForPersistence(PSDriveInfo drive)
{
bool isSupportedDriveForPersistence = false;
if (drive != null && !string.IsNullOrEmpty(drive.Name) && drive.Name.Length == 1)
{
char driveChar = Convert.ToChar(drive.Name, CultureInfo.InvariantCulture);

if (char.ToUpperInvariant(driveChar) >= 'A' && char.ToUpperInvariant(driveChar) <= 'Z')
{
isSupportedDriveForPersistence = true;
}
}

return isSupportedDriveForPersistence;
return drive is { Name.Length: 1 } && char.IsAsciiLetter(drive.Name[0]);
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@iSazonov iSazonov Oct 22, 2025

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The same about pattern.

}

/// <summary>
Expand Down
10 changes: 1 addition & 9 deletions src/System.Management.Automation/utils/PathUtils.cs
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Expand Up @@ -794,14 +794,6 @@ private static bool EndsWithPeriodOrSpace(string? path)
return c == ' ' || c == '.';
}

/// <summary>
/// Returns true if the given character is a valid drive letter
/// </summary>
private static bool IsValidDriveChar(char value)
{
return ((value >= 'A' && value <= 'Z') || (value >= 'a' && value <= 'z'));
}

private static bool IsDevice(string path)
{
return IsExtended(path)
Expand Down Expand Up @@ -859,7 +851,7 @@ private static bool IsPartiallyQualified(string path)
&& IsDirectorySeparator(path[2])
// To match old behavior we'll check the drive character for validity as the path is technically
// not qualified if you don't have a valid drive. "=:\" is the "=" file's default data stream.
&& IsValidDriveChar(path[0]));
&& char.IsAsciiLetter(path[0]));
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@iSazonov iSazonov Oct 22, 2025

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Please keep old method name for readability but update implementation.

}
/// <summary>
/// True if the given character is a directory separator.
Expand Down