node:http incorrectly send Transfer-Encoding: chunked even if no body is written

[osddeitf]

Original issue: #20033.

After debugging for a while, I found out that the HTTP PUT request was sent with Transfer-Encoding: chunked header, although the body is empty.

Which is different from Nodejs behavior:
The header is only added by the first calling request.write(chunk):

If no Content-Length is set, data will automatically be encoded in HTTP Chunked transfer encoding, so that server knows when the data ends. The Transfer-Encoding: chunked header is added.

These are the headers Nodejs would send (PUT with no body):

Headers {
  connection: "close",
  "content-length": "0",
  "content-type": "text/plain",
  host: "127.0.0.1:8001"
}

And these are the headers by Deno:

Headers {
  accept: "*/*",
  "accept-encoding": "gzip, br",
  "content-type": "text/plain",
  host: "127.0.0.1:8001",
  "transfer-encoding": "chunked",
  "user-agent": "Deno/1.36.0"
}

I tried digging into Deno source code to investigate the issue, and found that currently all POST, PATCH and PUT requests will be considered to have body:

• ext/node/polyfills/http.ts

    this._req = core.ops.op_node_http_request(
      this.method,
      url,
      headers,
      client.rid,
      this.method === "POST" || this.method === "PATCH" ||
        this.method === "PUT",
    )

• ext/node/ops/http.rs (these lines are useless as a result)

    // POST and PUT requests should always have a 0 length content-length,
    // if there is no body. https://fetch.spec.whatwg.org/#http-network-or-cache-fetch
    if matches!(method, Method::POST | Method::PUT) {
      request = request.header(CONTENT_LENGTH, HeaderValue::from(0));
    }

I don't know how to change the code to fix the issue yet. But I think of 2 ways:

• Add hasBody and hasContentTypeHeader flags then check them in request.write function to add Transfer-Encoding: chunked (but I don't know whether the reqwest crate supports adding header after started).
• Only start sending reqwest after the first call to request.write.

I'd appreciate any help to implement this.

[bartlomieju]

CC @crowlKats can you take a look and provide some pointers for @osddeitf to fix it?

[osddeitf]

The current behavior in nodejs is waiting for the first body chunk, or socket close(), until then the headers would be sent:

• lib/_http_outgoing.js

  this._header = header + '\r\n';
  this._headerSent = false;

  // Wait until the first body chunk, or close(), is sent to flush,
  // UNLESS we're sending Expect: 100-continue.
  if (state.expect) this._send('');