HttpResponseStreamWriter should override TextWriter.WriteLineAsync(string)

[madelson]

Describe the bug

A clear and concise description of what the bug is.

We have code generating a large response using a TextWriter which is an instance of HttpResponseStreamWriter. When the response gets large enough, the code starts failing with the following error:

Exception Type: System.InvalidOperationException
Error message: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 count)
at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(String value)
at <OUR CODE>

Interestingly, our code is failing on the following line:

await writer.WriteLineAsync($"...");

Digging in deeper, it seems like this fails because HttpResponseStreamWriter overrides TextWriter.WriteLineAsync(ReadOnlyMemory<char>, CancellationToken) and TextWriter.WriteAsync(string) but not TextWriter.WriteLineAsync(string). It is missing a few other async overloads as well.

This feels like an oversight; it makes it difficult to properly use the HttpResponseStreamWriter for async writes because WriteLineAsync(string) is a gotcha.

To Reproduce

Create a controller with the following endpoint:

	[HttpGet("repro")]
	public async Task<IActionResult> Repro()
	{
		await using var writer = new HttpResponseStreamWriter(this.Response.Body, Encoding.UTF8);
		await writer.WriteAsync(DateTime.Now.ToString());
		await writer.WriteLineAsync(new string('a', 20000)); // fails
                    // await writer.WriteLineAsync(new string('a', 20000).AsMemory()); // works
		return this.Ok();
	}

Exceptions (if any)

Exception Type: System.InvalidOperationException
Error message: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 count)
at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternal(Boolean flushEncoder)
at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(String value)
at System.IO.TextWriter.WriteLine(String value)
at System.IO.TextWriter.<>c.<WriteLineAsync>b__65_0(Object state)
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)

Further technical details

• ASP.NET Core version: 5
• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version: VS2019
• Include the output of dotnet --info:

dotnet --info Output

dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.400
 Commit:    d61950f9bf

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18363
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.400\

Host (useful for support):
  Version: 5.0.9
  Commit:  208e377a53

.NET SDKs installed:
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.509 [C:\Program Files\dotnet\sdk]
  2.1.511 [C:\Program Files\dotnet\sdk]
  2.1.512 [C:\Program Files\dotnet\sdk]
  5.0.101 [C:\Program Files\dotnet\sdk]
  5.0.400 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.29 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.29 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.29 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.18 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download