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VB -> C#: = "" should not be converted to string.IsNullOrEmpty when Option Compare Text #1089

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tats-u opened this issue Apr 6, 2024 · 0 comments
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VB -> C# Specific to VB -> C# conversion

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@tats-u
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tats-u commented Apr 6, 2024

VB.Net input code

Option Compare Text
Imports System
Imports Microsoft.VisualBasic

Public Class VisualBasicClass
    Public Shared Sub Main()
        Dim s = ChrW(&H2060) & ChrW(&H2060)
        Console.WriteLine(s = "")
        Console.WriteLine(s = Nothing)
    End Sub
End Class

https://sharplab.io/#v2:DYLgbgRgNALiBOBXAdgHwPIAcYEsD2yABAMJ4C2mAhvAKaEAqNAHjALABQAkhXvDAM6EAygE9+MGmQ7dMvAYQCyOAMbw8/PADMYAOgBqOfokrAAQpX4qOHAAqIIwFSWAXBBoyfOXlxF/34chEGEdg5OQgAW1DQAJsL2ipQ4yAAUAJSBwVkAIjhkhIIAvCQR8ADqKQBkABIATAAMAGz1aYSVJeVVdU0tmVlBpMgawDQ6ZfA4EgAyyTQpRYQARIsZ7P3Bg8Oj45M0M8hzCwByeDARyQDmq1kAoshxQvYcd3G+rkA==

True
False

Erroneous output

using Microsoft.VisualBasic; // Install-Package Microsoft.VisualBasic
using Microsoft.VisualBasic.CompilerServices; // Install-Package Microsoft.VisualBasic

public partial class VisualBasicClass
{
    public static void Main()
    {
        string s = Conversions.ToString(Strings.ChrW(0x2060)) + Strings.ChrW(0x2060);
        Console.WriteLine(string.IsNullOrEmpty(s));
        Console.WriteLine(string.IsNullOrEmpty(s));
    }
}
False
False

Expected output

using Microsoft.VisualBasic; // Install-Package Microsoft.VisualBasic
using Microsoft.VisualBasic.CompilerServices; // Install-Package Microsoft.VisualBasic

public partial class VisualBasicClass
{
    public static void Main()
    {
        string s = Conversions.ToString(Strings.ChrW(0x2060)) + Strings.ChrW(0x2060);
        Console.WriteLine(Operators.CompareString(s, "", true));
        Console.WriteLine(string.IsNullOrEmpty(s));
    }
}

Details

Strings composed of invisible characters (e.g. U+2060 and IVS (e.g. U+E0100)) are treated as equivalent to the empty string by VB only when Option Compare Text.
they are always told from null.

@tats-u tats-u added the VB -> C# Specific to VB -> C# conversion label Apr 6, 2024
@tats-u tats-u changed the title VB -> C#: _Add a short description_ VB -> C#: = "" should not be converted to string.IsNullOrEmpty when Option Compare Text Apr 6, 2024
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