dotnet/aspnetcore

`RouteHandlerBuilder.Accepts` does not return 415 response when the request has no `Content-Type`

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#45,264 opened on Nov 24, 2022

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Description

Is there an existing issue for this?

  • I have searched the existing issues

Describe the bug

This is probably a duplicate of #43794 but I would like to get further information on this issue, namely:

  1. If empty string is not in the list of content types to accept, why should empty string not be handled as 415?
  2. Given the current behavior of Accepts, is an explicit check for the existence of the Content-Type header required?

Code:

app.MapPut("/file", Created (HttpRequest request) =>
{
	return TypedResults.Created("https://example.org");
})
.WithOpenApi()
.Accepts<byte[]>("application/zip")
.Produces(StatusCodes.Status415UnsupportedMediaType);

Expected Behavior

415 Unsupported Media Type is returned.

Actual Behavior

201 Created is returned.

Steps To Reproduce

After dotnet run, make a PUT request with no header

Exceptions (if any)

No response

.NET Version

7.0.100

Anything else?

No response

Contributor guide

Tech stack
csharp
Domain
backendapi
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Basic understanding of ASP.NET Core Minimal APIsKnowledge of HTTP Content Type handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate the `Accepts` method implementation in the ASP.NET Core repository, specifically in the `RouteHandlerBuilder` class and the related middleware that checks the `Content Type` header against the accepted types. Look at the source code for `RequestDelegateFactory` or the `AcceptsMetadata` logic. The behavior should return 415 when the request has no `Content Type` header (or an empty string) and that value is not in the accepted list. Review linked issue #43794 for prior discussion. Consider modifying the check to treat missing or empty `Content Type` as unmatched unless an empty string is explicitly allowed.