fix(response-stream): fix response with no content doesn't correctly end the writable stream

[stackia]

Description of change

Previously we are detecting HTTP status codes that indicate no body (status >= 100 && status < 200 || status === 304 || status === 204 || method === 'HEAD'). This is not great since every HTTP status code can have empty body. It's totally legit to have a response with 200 status code but empty body.

Actually, the root cause of stream not being correctly ended, is that we skipped the 0\r\n\r\n right after the HTTP header:

As you can see in the screenshot (captured from AWS Lambda logs), for responses with empty body, the first write contains both headers and the chunk terminator 0\r\n\r\n.

This PR tries to detect that chunk terminator immediately after the headers, so we can close the stream correctly.

Tested working on AWS lambda with examples from https://github.com/H4ad/serverless-adapter-examples (fastify-aws-stream and nestjs-aws-stream).

Here is a before & after comparison.

Before (and the request just hang until Lambda timeout):

After:

Pull-Request Checklist

• Code is up-to-date with the main branch
• npm run lint passes with this change
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Added documentation inside www/docs/main folder.
• Included new files inside index.doc.ts.
• The new commits follow conventions outlined in the conventional commit spec

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.93%. Comparing base (250221f) to head (bded8cf).

Additional details and impacted files

@@            Coverage Diff            @@
##           main     #206       +/-   ##
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+ Coverage      0   99.93%   +99.93%     
=========================================
  Files         0       65       +65     
  Lines         0     7792     +7792     
  Branches      0      658      +658     
=========================================
+ Hits          0     7787     +7787     
- Misses        0        5        +5     

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[H4ad]

Hey, thanks for the detailed PR, looks very impressive!

I will take a deeper look at night, probably adding some tests just to ensure this is working fine but I will try to merge and release a new version as soon as possible.

[H4ad]

Thanks again for the contribution!

[H4ad]

Released at v4.2.1