validation_kit.go

package openapi3filter

import (
	"context"
	"encoding/json"
	"net/http"
)

///////////////////////////////////////////////////////////////////////////////////
// We didn't want to tie kin-openapi too tightly with go-kit.
// This file contains the ErrorEncoder and DefaultErrorEncoder function
// borrowed from this project.
//
// The MIT License (MIT)
//
// Copyright (c) 2015 Peter Bourgon
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
///////////////////////////////////////////////////////////////////////////////////

// ErrorEncoder is responsible for encoding an error to the ResponseWriter.
// Users are encouraged to use custom ErrorEncoders to encode HTTP errors to
// their clients, and will likely want to pass and check for their own error
// types. See the example shipping/handling service.
type ErrorEncoder func(ctx context.Context, err error, w http.ResponseWriter)

// StatusCoder is checked by DefaultErrorEncoder. If an error value implements
// StatusCoder, the StatusCode will be used when encoding the error. By default,
// StatusInternalServerError (500) is used.
type StatusCoder interface {
	StatusCode() int
}

// Headerer is checked by DefaultErrorEncoder. If an error value implements
// Headerer, the provided headers will be applied to the response writer, after
// the Content-Type is set.
type Headerer interface {
	Headers() http.Header
}

// DefaultErrorEncoder writes the error to the ResponseWriter, by default a
// content type of text/plain, a body of the plain text of the error, and a
// status code of 500. If the error implements Headerer, the provided headers
// will be applied to the response. If the error implements json.Marshaler, and
// the marshaling succeeds, a content type of application/json and the JSON
// encoded form of the error will be used. If the error implements StatusCoder,
// the provided StatusCode will be used instead of 500.
func DefaultErrorEncoder(_ context.Context, err error, w http.ResponseWriter) {
	contentType, body := "text/plain; charset=utf-8", []byte(err.Error())
	if marshaler, ok := err.(json.Marshaler); ok {
		if jsonBody, marshalErr := marshaler.MarshalJSON(); marshalErr == nil {
			contentType, body = "application/json; charset=utf-8", jsonBody
		}
	}
	w.Header().Set("Content-Type", contentType)
	if headerer, ok := err.(Headerer); ok {
		for k, values := range headerer.Headers() {
			for _, v := range values {
				w.Header().Add(k, v)
			}
		}
	}
	code := http.StatusInternalServerError
	if sc, ok := err.(StatusCoder); ok {
		code = sc.StatusCode()
	}
	w.WriteHeader(code)
	w.Write(body)
}