Default binder can use `UnmarshalParams(params []string) error` inter…

Default binder can use UnmarshalParams(params []string) error interface to bind multiple input values at one go.

Relates to https://github.com/labstack/echo/pull/2602

This allows developers to build fancy unmarsallers like related PR had. that turns /?a=1,2,3&a=4,5,6 into IntArrayB([]int{1, 2, 3, 4, 5, 6})

type IntArrayB []int

func (i *IntArrayB) UnmarshalParams(params []string) error {
    var numbers = make([]int, 0, len(params))

    for _, param := range params {
        var values = strings.Split(param, ",")
        for _, v := range values {
            n, err := strconv.ParseInt(v, 10, 64)
            if err != nil {
                return fmt.Errorf("'%s' is not an integer", v)
            }
            numbers = append(numbers, int(n))
        }
    }

    *i = append(*i, numbers...)
    return nil
}

func TestBindUnmarshalParams(t *testing.T) {
    t.Run("ok, target is an alias to slice and is nil, append multiple inputs", func(t *testing.T) {
        e := New()
        req := httptest.NewRequest(http.MethodGet, "/?a=1,2,3&a=4,5,6", nil)
        rec := httptest.NewRecorder()
        c := e.NewContext(req, rec)
        result := struct {
            V IntArrayB `query:"a"`
        }{}
        err := c.Bind(&result)

        assert.NoError(t, err)
        assert.Equal(t, IntArrayB([]int{1, 2, 3, 4, 5, 6}), result.V)
    })
}

labstack / echo

Default binder can use `UnmarshalParams(params []string) error` inter… #2607

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