c.Data and c.DataFromReader overwrite the set header

[alimoli]

Description

c.Data and c.DataFromReader overwrite the set header.

How to reproduce

package main

import (
	"bytes"
	"net/http"

	"github.com/gin-gonic/gin"
)

func main() {
	g := gin.Default()
	g.GET("/hello", func(c *gin.Context) {

		var compressedBuffer bytes.Buffer

		// Solution 1 (not working)
		contentLength := int64(compressedBuffer.Len())
		c.DataFromReader(
			http.StatusOK, contentLength, "text/csv", &compressedBuffer, map[string]string{
				"Content-Encoding": "gzip",
                                "X-Content-Encoding": "hawaii",
			},
		)

		// Solution 2 (not working)
		// c.Header("Content-Encoding", "gzip")
		// c.Data(http.StatusOK, "text/csv", compressedBuffer.Bytes())

	})
	g.Run(":9000")
}

Expectations

I expect to see the set headers in the response, but only Content-Type is set. I want to get also Content-Encoding.

Actual result

Only content type is set.

Environment

• go version: 1.22.1 darwin/arm64
• gin version (or commit ref): 1.9.1
• operating system: Mac OS Sonoma 14.2.1

[RedCrazyGhost]

I tested the code you provided and there is no problem. The return value of apifox is normal.
Please check the response header!
The code logic of gin code is normal.

Environment

• go version: go1.21.3 darwin/amd64
• gin version: github.com/gin-gonic/gin v1.9.1
• operating system: Mac OS 14.4.1

[alimoli]

@RedCrazyGhost I don't know exactly all the dynamics here, but I found the problem.
My testing client has no Accept-Encoding header in the request.
With that header in the request, the response includes the Content-Encoding.
Most of HTTP clients have this Accept-Encoding set to gzip, deflate by default.
This is why I haven't this problem in other situations.

Source: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Encoding#compressing_with_gzip