🐛 [Bug]: Using Head Method Header ContentLength always set and is not zero

[afifurrohman-id]

Bug Description

I don't know why fiber always Set Header ContentLength with non zero value, even using HEAD method

I have try using ctx.Send(nil) still same, even i set header manually ctx.Set(fiber.HeaderContentLength, "") still didn't work

How to Reproduce

Steps to reproduce the behavior:

1. Run test for code sample.

go test -v 

2. See..

=== RUN   TestHead
2023/11/04 05:35:45.740429 main_test.go:27: [Fatal] Expected Header ContentLength to zero, but got 18
exit status 1
FAIL    go-fiber-bug-head       0.641s

Expected Behavior

PASS, Header ContentLength is not set OR zero value

Fiber Version

v2.50.0

Code Snippet (optional)

package main

import (
        "testing"
        "net/http/httptest"
        "github.com/gofiber/fiber/v2"
        "github.com/gofiber/fiber/v2/log"
)

func TestHead(test *testing.T) {
        app := fiber.New()
        app.Head("/", func(ctx *fiber.Ctx) error {
                return ctx.SendStatus(fiber.StatusOK)
        })

        req := httptest.NewRequest(fiber.MethodGet, "/", nil)
        res, err := app.Test(req)
        if err != nil {
            log.Error(err)
        }


        contentLength :=  res.Header.Get(fiber.HeaderContentLength)
        if contentLength != "" {
                log.Fatalf("Expected Header ContentLength to zero, but got %s",contentLength)
        }

}

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my problem prior to opening this one.
• I understand that improperly formatted bug reports may be closed without explanation.

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[ReneWerner87]

It is an automatism, within our kernel, which sets this header automatically and is not a bug

This is intentional

[afifurrohman-id]

Ok so, how when i want to unset ContentLength header??

[ReneWerner87]

Why would you want to do that?

[ReneWerner87]

This is determined automatically based on the content.
I can send you an example later of how you can set it to 0, but not unset.

[ReneWerner87]

@afifurrohman-id

app.Head("/", func(ctx *fiber.Ctx) error {
    return ctx.Status(fiber.StatusOK).Send(nil)
})

app.Head("/", func(ctx *fiber.Ctx) error {
    // manipulation of the content length
    ctx.Response().Header.SetContentLength(10000)
    return ctx.Status(fiber.StatusOK).Send(nil)
})

[afifurrohman-id]

Okay cool, can you added to docs? May helpful for anyone with same question

[ReneWerner87]

if it comes up again, I'll add it