AllowSynchronousIO = false AND CacheTagHelper

[alienwareone]

CacheTagHelper doesn't work without AllowSynchronousIO = true;

Relevant Stacktrace:

System.InvalidOperationException: 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 System.IO.Compression.DeflateStream.WriteDeflaterOutput()
   at System.IO.Compression.DeflateStream.WriteCore(ReadOnlySpan`1 buffer)
   at System.IO.Compression.DeflateStream.Write(Byte[] array, Int32 offset, Int32 count)
   at System.IO.Compression.GZipStream.Write(Byte[] array, Int32 offset, Int32 count)
   at Microsoft.AspNetCore.ResponseCompression.ResponseCompressionBody.Write(Byte[] buffer, Int32 offset, Int32 count)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternal(Boolean flushEncoder)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(Char[] values, Int32 index, Int32 count)
   at Microsoft.AspNetCore.Mvc.TagHelpers.CacheTagHelper.CharBufferHtmlContent.WriteTo(TextWriter writer, HtmlEncoder encoder)

https://github.com/aspnet/Mvc/blob/04ce6cae44fb0cb11470c21769d41e3f8088e8aa/src/Microsoft.AspNetCore.Mvc.TagHelpers/CacheTagHelper.cs#L264

[mkArtakMSFT]

Thank you for filing this issue. In order for us to investigate this issue, please provide a minimalistic repro project (ideally a GitHub repo) that illustrates the problem.

[alienwareone]

Hope that helps:
https://github.com/alienwareone/CacheTagHelperAsyncIOBug

It has something to do with Controller.Action()->return ViewComponent()

System.InvalidOperationException: 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 System.IO.Compression.DeflateStream.WriteDeflaterOutput()
   at System.IO.Compression.DeflateStream.WriteCore(ReadOnlySpan`1 buffer)
   at System.IO.Compression.DeflateStream.Write(Byte[] array, Int32 offset, Int32 count)
   at System.IO.Compression.GZipStream.Write(Byte[] array, Int32 offset, Int32 count)
   at Microsoft.AspNetCore.ResponseCompression.ResponseCompressionBody.Write(Byte[] buffer, Int32 offset, Int32 count)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternal(Boolean flushEncoder)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(Char[] values, Int32 index, Int32 count)
   at Microsoft.AspNetCore.Mvc.TagHelpers.CacheTagHelper.CharBufferHtmlContent.WriteTo(TextWriter writer, HtmlEncoder encoder)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.Buffers.ViewBuffer.WriteToAsync(TextWriter writer, HtmlEncoder encoder)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewComponentResultExecutor.ExecuteAsync(ActionContext context, ViewComponentResult result)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewComponentResultExecutor.ExecuteAsync(ActionContext context, ViewComponentResult result)

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.