binder: make binding to Map work better with string destinations

[aldas]

Relates to #2552 and #988

Difference from previous implementations is that in case we are binding to unsupported Map we ended in with panic. Now we skip binding (params/query/header) and try other sources (ala body)

package main import ( "github.com/labstack/echo/v4" "github.com/labstack/echo/v4/middleware" "net/http" ) func main() { e := echo.New() e.Use(middleware.Logger()) e.Use(middleware.Recover()) // test: `curl -XPOST --header "Content-Type: application/json" -d '{"module1": "2", "module2": "3"}' http://127.0.0.1:8080/test/string/1` // output old: {"id":"1","module1":"2","module2":"3"} // output new: {"id":"1","module1":"2","module2":"3"} e.POST("/test/string/:id", func(c echo.Context) error { p := map[string]string{} if err := c.Bind(&p); err != nil { return err	} return c.JSON(http.StatusOK, p)	}) // test: `curl -XPOST --header "Content-Type: application/json" -d '{"module1": 2, "module2": 3}' http://127.0.0.1:8080/test/int/1` // output old: {"message":"Internal Server Error"} // output new: {"module1":"2","module2":"3"} e.POST("/test/int/:id", func(c echo.Context) error { p := map[string]int{} if err := c.Bind(&p); err != nil { return err	} return c.JSON(http.StatusOK, p)	}) e.Start("127.0.0.1:8080") }

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (584cb85) 92.89% compared to head (aea150e) 93.02%.

Additional details and impacted files

@@ Coverage Diff @@ ## master #2554 +/- ## ========================================== + Coverage 92.89% 93.02% +0.12%  ========================================== Files 39 39 Lines 4658 4673 +15 ========================================== + Hits 4327 4347 +20  + Misses 240 236 -4  + Partials 91 90 -1 

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[astromechza]

Thanks @aldas, this looks much more robust than before 👍

[georgmu]

There is still an issue when having code like this:

var params map[string]any c.Bind(&params) 

This works for JSON body, but fails for path params (since params is nil).

A small addition helps to solve this (this is the same that the JSON decoder does):

--- a/bind.go +++ b/bind.go @@ -138,6 +138,9 @@ func (b *DefaultBinder) bindData(destination interface{}, data map[string][]stri // You are better off binding to struct but there are user who want this map feature. Source of data for these cases are: // params,query,header,form as these sources produce string values, most of the time slice of strings, actually. if typ.Kind() == reflect.Map && typ.Key().Kind() == reflect.String { + if val.IsNil() { + val.Set(reflect.MakeMap(typ)) + } k := typ.Elem().Kind() isElemInterface := k == reflect.Interface isElemString := k == reflect.String 

I can prepare a merge request (including a test case) for this.

[dakhtarovpx]

Hello there!

Thank you for your PR.

I'd like to ask: when do you plan to release this PR? v4.11.4 is the latest version, and it still doesn't work at the moment.

[aldas]

I do not know at the moment. Meanwhile use:

p := map[string]string{} if err := c.Bind(&p); err != nil {