Support removing 'value' attribute

[jirisykora83]

Runtime Environment:
OS Name: Windows
OS Version: 10.0.16299
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\2.1.300-preview2-008533\

Repro

@page "/"

<input value="@Text" onchange="@onTextChange" />
<div>Currently text: @Text</div>
<div onclick="@onButtonClick">SET TEXT TO NULL</div>

@{ 
	Console.WriteLine($"Render with: '{Text ?? "NULL"}'");
}

@functions
{
	public string Text { get; set; }

	protected void onTextChange(UIChangeEventArgs e)
	{
		Text = (string)e.Value;
	}

	protected void onButtonClick()
	{
		Text = null;
	}
}

When i type some text to input (click outside for call "onchange"). And then i click to "SET TEXT TO NULL". In console i see Render with: 'NULL' but input keep last value.

It fail same if i use <input bind="@Text" /> (and remove onTextChange).

Excepted behavior

Reset input text. (same like for <div>@Text</div>).

Workaround

<input value="@(Text ?? string.Empty)" onchange="@onTextChange" />

[SteveSandersonMS]

Thanks for reporting this, @jirisykora83!

This is caused by BrowserRenderer.ts having special support for setting element values, but not having equivalent support for removing those values.