Regression: binding a map is not allowed anymore

[jinroh]

Issue Description

I think a valid use case of binding to a map[string]interface{} now causes the following error: Binding element must be a struct. I think the regression has been caused by #972.

Is this use case still valid ?

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

Binding a map[string]interface{} is valid.

Actual behaviour

Binding a map[string]interface{} causes an error.

Code to debug

package main

func handler(c echo.Context) {
  var m map[string]interface{}
  if err := c.Bind(&m); err != nil {
    // err is "Binding element must be a struct"
  }
  return nil
}

Version/commit

1e9845a

[narrowizard]

Has this issue been solved? I meet it today. my code as following:

• https://play.golang.org/p/qyY4UKNvZ6B

maybe you need to repear it locally since go playground cannot listen port.
@vishr

[thanhps42]

Has this issue been solved? I meet it today. my code as following:

• https://play.golang.org/p/qyY4UKNvZ6B

maybe you need to repear it locally since go playground cannot listen port.
@vishr

me too

[vishr]

I am not sure what is the issue but the following code works

package main

import (
	"net/http"
	"github.com/labstack/echo"
)

func main() {
	e := echo.New()
	e.GET("/test", func(c echo.Context) error {
		p := map[string]interface{}{}
		if err := c.Bind(&p); err != nil {
			return err
		}
		return c.JSON(http.StatusOK, p)
	})

	e.Start("127.0.0.1:8080")
}

curl -X GET \
  http://localhost:8080/test \
  -H 'Content-Type: application/json' \
  -d '{
	"a": 1,
	"b": 2
}'

[narrowizard]

thanks for your reply,
and your eg works fine.
it seems that bind to map only works when content-type is application/json, does it?

[vishr]

How are you sending the data?

[narrowizard]

i've tested both following format:

• curl -X GET -H 'Content-Type: application/x-www-form-urlencoded' http://localhost:8080/test?a=1&b=2
• curl -X GET http://localhost:8080/test -H 'Content-Type: application/x-www-form-urlencoded' -d 'a=1&b=2'

and echo returns binding element must be a struct error.

[narrowizard]

after a deep dive to echo.
I find that ctx.Bind returns err in some situation with a map destination.

• In a GET or DELETE request without request body.
  

  echo/bind.go

  Lines 47 to 49 in 01229ec

  	if req.ContentLength == 0 {
  	if req.Method == http.MethodGet || req.Method == http.MethodDelete {
  	if err = b.bindData(i, c.QueryParams(), "query"); err != nil {

• In a request with Content-Type: application/form-data or application/x-www-form-urlencoded.
  

  echo/bind.go

  Lines 76 to 81 in 01229ec

  	case strings.HasPrefix(ctype, MIMEApplicationForm), strings.HasPrefix(ctype, MIMEMultipartForm):
  	params, err := c.FormParams()
  	if err != nil {
  	return NewHTTPError(http.StatusBadRequest, err.Error()).SetInternal(err)
  	}
  	if err = b.bindData(i, params, "form"); err != nil {

  
  

  echo/bind.go

  Lines 97 to 99 in 01229ec

  	if typ.Kind() != reflect.Struct {
  	return errors.New("binding element must be a struct")
  	}

Do it possible to support Map in DefaultBinder? or this will cause some other issues? @vishr

[vishr]

@narrowizard Just push a fix, let me know how it works out for you.