Binding into a pointer to a slice returns an error "unknown type"

maticmeznar commented 1 year ago

Issue Description

When binding input data into a struct with a field with a pointer to a slice, *[]string for example, Bind method returns "unknown type" error.

Checklist

[X] Dependencies installed
[X] No typos
[X] Searched existing issues and docs

Expected behaviour

Successfully bind input data into the provided struct

Actual behaviour

Bind method returns "unknown type" error

Steps to reproduce

package echotest

import (
    "net/http"
    "net/http/httptest"
    "net/url"
    "testing"

    "github.com/davecgh/go-spew/spew"
    "github.com/labstack/echo/v4"
    "github.com/stretchr/testify/assert"
)

type (
    InputData struct {
        Tags *[]string `json:"tags" query:"tags"`
    }

    handler struct{}
)

func (h *handler) testHandler1(c echo.Context) error {
    data := new(InputData)
    if err := c.Bind(data); err != nil {
        return err
    }

    spew.Dump(data)

    return c.JSON(http.StatusOK, data)
}

func TestTest(t *testing.T) {
    e := echo.New()

    q := make(url.Values)
    q.Add("tags", "testing")
    q.Add("tags", "server")

    req := httptest.NewRequest(http.MethodGet, "/?"+q.Encode(), nil)
    // req.Header.Set(echo.HeaderContentType, echo.MIMEApplicationJSON)
    rec := httptest.NewRecorder()
    c := e.NewContext(req, rec)

    h := &handler{}
    if assert.NoError(t, h.testHandler1(c)) {
        assert.Equal(t, http.StatusOK, rec.Code)
    }
}

Version/commit

v4.9.1

aldas commented 1 year ago

Changing that field from *[]string to []string should do the trick. At the moment binder knows to only to handle pointers to common types ala string,bool, structs etc and not their slice variants.

InputData struct {
        Tags []string `json:"tags" query:"tags"`
    }

Anyway, I think you are overthinking here with pointers. Unitilialized slice is nil. So if that testcase would have no tags query params this would be after bind:

Couple of articles about empty slices:

maticmeznar commented 1 year ago

Thank you for the reply. The problem is that the struct is automatically generated by oapi-codegen and it creates a pointer unless I set the field as required in the OpenAPI spec.

I was hoping this was a bug since binding into a pointer to a slice works with JSON in the request body.

aldas commented 1 year ago

I'll take a look we probably can do something with binder.

for history sake: pointer to slice related issue https://github.com/deepmap/oapi-codegen/issues/266

labstack / echo