The differences between http2 compatibility API and http[s]

[sogaani]

Thanks to the efforts of making the compatibility API, differences between http[s] and http2 modules seldom annoy developers.
But, some http2 compatibility API still behaves differently and lacks some APIs from http[s] and it causes breakages to ecosystems for http[s](e.g. expressjs/express#3730).

In order to expose the differences, I've been translating test cases for http[s] to test cases for http2 at my repo. The following is a list of the differences currently founded by translated test cases.

I'm not sure all the differences have to be fixed. I thought if they should not be fixed, documenting the differences is good for the developer.

Differences between http and http2 compatibility API

• http2.Http2ServerRequest does not have req.connection.bytesWritten. test:parallel/test-http-byteswritten.js,parallel/test-https-byteswritten.js
• If http2.Http2ServerRequest.pause is called, http2.Http2ServerRequest.socket never emit 'data' event. test:parallel/test-http-dump-req-when-res-ends.js
• http2.Http2ServerResponse.writeHead with 'HTTP/1 Connection specific headers'(e.g. "Transfer-Encoding":"chunked") causes error:ERR_HTTP2_INVALID_CONNECTION_HEADERS. test:parallel/test-http-head-request.js
• http2.Http2ServerResponse does not have res.writeProcessing. test:parallel/test-http-information-processing.js
• http2.Http2ServerResponse.writeHead with a spaced header name does not cause error. test:parallel/test-http-invalidheaderfield.js
• http2.Http2ServerRequest does not have req.connection.parser. test:parallel/test-http-highwatermark.js,parallel/test-http-server-keepalive-end.js
• http2.Http2ServerResponse.end calls callback before satisfying condition of 'finish' events. test:parallel/test-http-outgoing-finish.js
• http2.Http2ServerResponse.getHeaders returns headers which is not initialized by Object.create(null)
  test:parallel/test-http-mutable-headers.js
• http2.Http2ServerResponse does not have res.writableHighWaterMark. test:parallel/test-http-outgoing-properties.js related issue:http: OutgoingMessage streamlike #28969
• http2.Http2ServerResponse does not have res.writableLength. test:parallel/test-http-outgoing-properties.js related issue:http: OutgoingMessage streamlike #28969
• http2.Http2ServerResponse does not have res.writableFinished. test:parallel/test-http-outgoing-writableFinished.js related issue:http2 compat missing writableFinished #29230
• http2.Http2ServerRequest.headers returns headers which is initialized by Object.create(null)
  test:parallel/test-http-raw-headers.js
• http2.Http2ServerResponse.removeHeader cannot remove a header nodejs automatically adds(e.g. 'date'). test:parallel/test-http-remove-header-stays-removed.js
• http2.Http2ServerResponse.write after http2.Http2ServerResponse.end returns false. test:parallel/test-http-res-write-after-end.js
• http2.Http2ServerResponse.write after http2.Http2ServerResponse.end does not emmit 'error'. test:parallel/test-http-res-write-after-end.js,parallel/test-http-server-write-after-end.js Fixed by http2: make http2/compat.write more http/1 compliant #30964
• http2.Http2ServerResponse.write with array input does not cause an error. test:parallel/test-http-res-write-after-end.js
• http2.Http2ServerResponse.end with array input does not cause an error. test:parallel/test-http-res-write-after-end.js
• http2.Http2ServerResponse's error code start with 'ERR_HTTP2'. test:parallel/test-http-response-add-header-after-sent.js,parallel/test-http-response-remove-header-after-sent.js,parallel/test-http-response-statuscode.js,parallel/test-http-write-head.js
• http2.Http2ServerResponse.setHeader and http2.Http2ServerResponse.writeHead with multiple value of 'content-length' causes an error. test:parallel/test-http-response-multi-content-length.js
• http2.Http2ServerResponse.setHeader and http2.Http2ServerResponse.writeHead with multiple value of 'content-type' or other headers expected single value causes an error. test:parallel/test-http-response-multiheaders.js
• http2.Http2ServerResponse.writeHead with invalid character does not cause error. test:parallel/test-http-response-splitting.js
• http2.Http2ServerResponse sending 'Trailer' header without 'transfer encoding: chunked' does not cause error. test:parallel/test-http-server-de-chunked-trailer.js
• http2.Http2ServerResponse.writeHead cannot set multiple value of header with nested array. test:parallel/test-http-set-cookies.js
• http2.Http2ServerResponse.setTimeout does not pass a socket to cb function. test:parallel/test-http-set-timeout-server.js
• http2.Http2ServerResponse.writeHead with invalid status message does not cause an error. test:parallel/test-http-status-reason-invalid-chars.js
• stream.pipe(http2.Http2ServerResponse) eventually emmits both 'finish' and 'close' events. test:parallel/test-http-writable-true-after-close.js
• http2.Http2ServerResponse.end does not execute callback when http2.Http2ServerResponse.end has already been called. test:parallel/test-http-outgoing-end-multiple.js related PR:[x] http2: compat ERR_STREAM_ALREADY_FINISHED #29229
• After http2.Http2ServerRequest.connection.setTimeout is called, 'timeout' event is not emitted. test:parallel/test-http-set-timeout.js
• http2.Http2ServerResponse.finished turn true without calling end.
  http2: make compat finished match http/1 #24347
• http2.Http2ServerResponse.write throw err when connection is invalid. http1 do nothing then.
  HTTP2 compatibility layer issues with invalid streams #29529
• compat mode http2.Http2Server emits error when a connection is unexpectedly closed. In that case, http1.Server emits aborted. http2: sessionError vs aborted #28267
• http2.Http2ServerResponse.write(data) after http2.Http2ServerResponse.writeHead()
  with status 304 or 204 cause error. Fix usage of undocumented _implicitHeader expressjs/compression#128 (comment)

[ronag]

I think you can add #24347 to the list as well.

[ronag]

Really good work! I would be interested in helping sorting some of this.

[ronag]

@sogaani I would like to suggest we put your tests in under tests/known_issues so that we might sort them out later? @addaleax would you agree?

[ronag]

Here is another one that might be worth to add to the list, #29529

[sogaani]

@ronag Thank you for looking at this issue. I added 2 issues you mentioned.

I'm glad to make pull request to put my tests at this repo if it is OK.

[ronag]

@addaleax Some guidance here? Would it make sense to add @sogaani's test in e.g. known_issues? Sorting all these out will probably take a while and I'd like to avoid losing this excellent work.

[ronag]

@sogaani: Another candidate for the list #28267

[ronag]

@sogaani: Just wanted to give a quick ping that I'm still interested in helping sorting these out over time (a little swamped at the moment). But please do continue updating the list if you find more differences.

[sogaani]

@ronag Thank you for mentioning the difference. I added :)

[ronag]

@rexagod: If you are looking for tasks there is plenty to pick from here.

[rexagod]

Awesome! Thank you for pointing me here, @ronag!

[markb-trustifi]

http2.Http2ServerResponse does not have res.writeProcessing

Isn't the 102 status code is totally deprecated and will not be added to HTTP/2 standard?
https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/102#browser_compatibility
Maybe it should be replaced with multiple res.write()?