Breaking change in .NET 5 affects string comparisons in PowerShell 7.1.2+

[sdwheeler]

Prerequisites

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Summary of the new feature or changed behavior

With string operands, PowerShell's -eq operator (and its inverse, -ne), performs case-insensitive, culture-invariant string comparison (StringComparison.InvariantCultureIgnoreCase).

As of .NET 5.0, the runtime underlying PowerShell 7.1, this method appears to ignore non-printing control characters. Earlier versions, including up to (at least) 3.1.2 (underlying PowerShell 7.0.5) and the .NET Framework version underlying Windows PowerShell do not.

For instance:

# Escape sequence "`a" is [char] 7
'Food' -eq "Foo`ad"   # !! $true in .NET 5+ - the non-printing control character is *ignored*

// C# equivalent
"Food".Equals("Foo\ad", StringComparison.InvariantCultureIgnoreCase)

List of articles that need to be updated

• https://docs.microsoft.com/powershell/scripting/whats-new/what-s-new-in-powershell-71#breaking-changes-and-improvements
• https://docs.microsoft.com/powershell/scripting/whats-new/differences-from-windows-powershell

Link to related PR in PowerShell/PowerShell repo

n/a

Link to related Issues in PowerShell/PowerShell repo

PowerShell/PowerShell#14956 (comment)

[sdwheeler]

Need to link to

• https://docs.microsoft.com/dotnet/standard/base-types/string-comparison-net-5-plus
• https://docs.microsoft.com/dotnet/core/extensions/globalization-icu