api.go

Documentation: github.com/go-openapi/errors

     1  // Copyright 2015 go-swagger maintainers
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package errors
    16  
    17  import (
    18  	"encoding/json"
    19  	"fmt"
    20  	"net/http"
    21  	"reflect"
    22  	"strings"
    23  )
    24  
    25  // DefaultHTTPCode is used when the error Code cannot be used as an HTTP code.
    26  var DefaultHTTPCode = http.StatusUnprocessableEntity
    27  
    28  // Error represents a error interface all swagger framework errors implement
    29  type Error interface {
    30  	error
    31  	Code() int32
    32  }
    33  
    34  type apiError struct {
    35  	code    int32
    36  	message string
    37  }
    38  
    39  func (a *apiError) Error() string {
    40  	return a.message
    41  }
    42  
    43  func (a *apiError) Code() int32 {
    44  	return a.code
    45  }
    46  
    47  // MarshalJSON implements the JSON encoding interface
    48  func (a apiError) MarshalJSON() ([]byte, error) {
    49  	return json.Marshal(map[string]interface{}{
    50  		"code":    a.code,
    51  		"message": a.message,
    52  	})
    53  }
    54  
    55  // New creates a new API error with a code and a message
    56  func New(code int32, message string, args ...interface{}) Error {
    57  	if len(args) > 0 {
    58  		return &apiError{
    59  			code:    code,
    60  			message: fmt.Sprintf(message, args...),
    61  		}
    62  	}
    63  	return &apiError{
    64  		code:    code,
    65  		message: message,
    66  	}
    67  }
    68  
    69  // NotFound creates a new not found error
    70  func NotFound(message string, args ...interface{}) Error {
    71  	if message == "" {
    72  		message = "Not found"
    73  	}
    74  	return New(http.StatusNotFound, fmt.Sprintf(message, args...))
    75  }
    76  
    77  // NotImplemented creates a new not implemented error
    78  func NotImplemented(message string) Error {
    79  	return New(http.StatusNotImplemented, message)
    80  }
    81  
    82  // MethodNotAllowedError represents an error for when the path matches but the method doesn't
    83  type MethodNotAllowedError struct {
    84  	code    int32
    85  	Allowed []string
    86  	message string
    87  }
    88  
    89  func (m *MethodNotAllowedError) Error() string {
    90  	return m.message
    91  }
    92  
    93  // Code the error code
    94  func (m *MethodNotAllowedError) Code() int32 {
    95  	return m.code
    96  }
    97  
    98  // MarshalJSON implements the JSON encoding interface
    99  func (m MethodNotAllowedError) MarshalJSON() ([]byte, error) {
   100  	return json.Marshal(map[string]interface{}{
   101  		"code":    m.code,
   102  		"message": m.message,
   103  		"allowed": m.Allowed,
   104  	})
   105  }
   106  
   107  func errorAsJSON(err Error) []byte {
   108  	//nolint:errchkjson
   109  	b, _ := json.Marshal(struct {
   110  		Code    int32  `json:"code"`
   111  		Message string `json:"message"`
   112  	}{err.Code(), err.Error()})
   113  	return b
   114  }
   115  
   116  func flattenComposite(errs *CompositeError) *CompositeError {
   117  	var res []error
   118  	for _, er := range errs.Errors {
   119  		switch e := er.(type) {
   120  		case *CompositeError:
   121  			if e != nil && len(e.Errors) > 0 {
   122  				flat := flattenComposite(e)
   123  				if len(flat.Errors) > 0 {
   124  					res = append(res, flat.Errors...)
   125  				}
   126  			}
   127  		default:
   128  			if e != nil {
   129  				res = append(res, e)
   130  			}
   131  		}
   132  	}
   133  	return CompositeValidationError(res...)
   134  }
   135  
   136  // MethodNotAllowed creates a new method not allowed error
   137  func MethodNotAllowed(requested string, allow []string) Error {
   138  	msg := fmt.Sprintf("method %s is not allowed, but [%s] are", requested, strings.Join(allow, ","))
   139  	return &MethodNotAllowedError{
   140  		code:    http.StatusMethodNotAllowed,
   141  		Allowed: allow,
   142  		message: msg,
   143  	}
   144  }
   145  
   146  // ServeError implements the http error handler interface
   147  func ServeError(rw http.ResponseWriter, r *http.Request, err error) {
   148  	rw.Header().Set("Content-Type", "application/json")
   149  	switch e := err.(type) {
   150  	case *CompositeError:
   151  		er := flattenComposite(e)
   152  		// strips composite errors to first element only
   153  		if len(er.Errors) > 0 {
   154  			ServeError(rw, r, er.Errors[0])
   155  		} else {
   156  			// guard against empty CompositeError (invalid construct)
   157  			ServeError(rw, r, nil)
   158  		}
   159  	case *MethodNotAllowedError:
   160  		rw.Header().Add("Allow", strings.Join(e.Allowed, ","))
   161  		rw.WriteHeader(asHTTPCode(int(e.Code())))
   162  		if r == nil || r.Method != http.MethodHead {
   163  			_, _ = rw.Write(errorAsJSON(e))
   164  		}
   165  	case Error:
   166  		value := reflect.ValueOf(e)
   167  		if value.Kind() == reflect.Ptr && value.IsNil() {
   168  			rw.WriteHeader(http.StatusInternalServerError)
   169  			_, _ = rw.Write(errorAsJSON(New(http.StatusInternalServerError, "Unknown error")))
   170  			return
   171  		}
   172  		rw.WriteHeader(asHTTPCode(int(e.Code())))
   173  		if r == nil || r.Method != http.MethodHead {
   174  			_, _ = rw.Write(errorAsJSON(e))
   175  		}
   176  	case nil:
   177  		rw.WriteHeader(http.StatusInternalServerError)
   178  		_, _ = rw.Write(errorAsJSON(New(http.StatusInternalServerError, "Unknown error")))
   179  	default:
   180  		rw.WriteHeader(http.StatusInternalServerError)
   181  		if r == nil || r.Method != http.MethodHead {
   182  			_, _ = rw.Write(errorAsJSON(New(http.StatusInternalServerError, err.Error())))
   183  		}
   184  	}
   185  }
   186  
   187  func asHTTPCode(input int) int {
   188  	if input >= 600 {
   189  		return DefaultHTTPCode
   190  	}
   191  	return input
   192  }
   193
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