HTTP Header with case-insensitive header names

Hi, i’ve discovered another minor issue.

Describe the bug define content-type: text/html as response header results in duplicate content type header:

To Reproduce create a route that returns a html response like

  return ({
      headers: {
          ...filterProxyRequestHeaders(response.headers),
          "content-type": "text/html"
      },
      body: bodyStream
  });

Expected behavior response contains only "content-type": "text/html" as content type header.

Desktop (please complete the following information):

• OS => MacOS BigSur
• Package + Version

   "@marblejs/core": "^3.4.8",
   "@marblejs/middleware-body": "^3.4.8",
   "@marblejs/middleware-logger": "^3.4.8",

• Node version => v14.12.0

Additional context i found this one as a short explainer that the headers in http protocol are case-insensitive: https://stackoverflow.com/a/5259004

My use case for a bit more context: I use undici a nodejs http client: https://github.com/nodejs/undici All response headers are in lower case letters and my plan is to forward them, as my marble server acts like a proxy in this case.

Workaround For now i can map the content-type header to the upper case one. But this can be tedious process if more headers are affected.

Let me know if i can help with that if you want to improve this.

[DawidYerginyan]

Even tho It is technically a bugfix and a non breaking change according to the HTTP Spec I’d opt to introduce it gradually for the ☝🏻 mentioned reasons with service2service communication and test cases. I propose to patch the behavior change under a feature-toggle disabled by default with a sufficient warning linking to the issue, stating that It is going to be the default behavior in the X upcoming version and introduce it as a breaking change in the next minor/major.

One option would be to control it with an env variable, something like

MARBLE_HTTP_CASE_INSENSITIVE_HEADER_NAMES=true

Considering that the change affects only the HTTP server, It could also be a temporary optional server factory parameter

import { createServer } from '@marblejs/core';

const httpServer = createServer({
  port,
  listener,
  dependencies,
  options: {
    httpsOptions,
    caseInsensitiveHeaderNames: true,
  },
});

[alexanderbartels]

sorry for the late response - its a bit crazy at work currently. @JozefFlakus if you haven’t started yet, i can have a look at this in the upcoming weekend.

I like the idea from @DawidYerginyan to use a feature flag. I think an env variable would be a proper choice. With this solution the code must not be touched twice.