Console.In.Peek() always returning EOF after the first read line on Windows

[eiriktsarpalis]

I came across the following behaviour when debugging a System.Console test. Running

static void Main()
{
    while (true)
    {
        Console.Write("Enter some text: ");
        int c = Console.In.Peek();
        string? line = Console.In.ReadLine();
        Console.WriteLine($"Peek: {c} ReadLine: {line}");
    }
}

Produces the following behaviour

Enter some text: test
Peek: 116 ReadLine: test
Enter some text: test
Peek: -1 ReadLine: test
Enter some text: test
Peek: -1 ReadLine: test

Essentially it is impossible to use Console.In.Peek() after the first line has been consumed. Note that this behaviour manifests itself regardless of whether the buffer contains any characters. The following variant will produce the exact same observable behaviour:

static void Main()
{
    while(true)
    {
        Console.Write("Enter some text: ");
        int c = MyPeek();
        string? line = Console.In.ReadLine();
        Console.WriteLine($"Peek: {c} ReadLine: {line}");
    }

    static int MyPeek()
    {
        while (!Console.KeyAvailable)
        {
            Thread.Sleep(10);
        }
        return Console.In.Peek();
    }
}

Note that unix does not have the same behaviour.

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[eiriktsarpalis]

Related to #39192.

[adamsitnik]

I assume that this is not a regression and moving it to future

[eiriktsarpalis]

I assume that this is not a regression and moving it to future

That's correct, this seems to have been the behaviour for quite a while. The main goal here is achieving consistency with unix behaviour.