Content-Length header missing for empty POST requests

[N1cOs]

Hello! Recently we faced with a problem, that resty Client doesn't set Content-Length header for an empty POST request.

Version - 2.16.5.

Example:

package main

import (
	"fmt"

	"github.com/go-resty/resty/v2"
)

func main() {
	client := resty.New()

	client.OnBeforeRequest(func(client *resty.Client, request *resty.Request) error {
		request.
			SetBody(nil).
			SetContentLength(true)

		return nil
	})

	client = client.SetBaseURL("http://localhost:8080")

	resp, err := client.R().Execute("POST", "/test")
	if err != nil {
		panic(err)
	}

	fmt.Println(resp)
}

Then I captured request with Wireshark and Content-Length header is missing:

[N1cOs]

I did a little more research. It happens not only for POST requests but also for PUT, PATCH.

From version v2.16.2 there is a workaround to use http.NoBody explicitly.

[Libero-Dev]

@N1cOs I have created a PR for this. Ultimately I'm not so sure if this is something that should or shouldn't be merged in and supported as the omission of the Content-Length header seems to be something of an undocumented (that or documentation on this is very difficult to find) side effect in the standard http library when the resty request is built with http.NewRequest.

[N1cOs]

@Libero-Dev thanks for the fix. IMO it should be fix. Standard http library has the logic for handling a nil body. For instance, this code snippet writes Content-Length header in the request:

package main

import "net/http"

func main() {
	_, err := http.Post("http://localhost:8080/test", "application/json", nil)
	if err != nil {
		panic(err)
	}
}

Library sends the request:

POST /test HTTP/1.1
Host: localhost:8080
User-Agent: Go-http-client/1.1
Content-Length: 0
Content-Type: application/json
Accept-Encoding: gzip

[jeevatkm]

This is fixed by PR #1003