distribution/registry/api/errcode/errors.go
Doug Davis 0a6a6f5b81 Move ErrorCode logic to new errcode package
Make HTTP status codes match the ErrorCode by looking it up in the Descriptors

Signed-off-by: Doug Davis <dug@us.ibm.com>
2015-05-26 13:18:54 -07:00

206 lines
5.1 KiB
Go

package errcode
import (
"fmt"
"net/http"
"strings"
)
// ErrorCode represents the error type. The errors are serialized via strings
// and the integer format may change and should *never* be exported.
type ErrorCode int
// ErrorDescriptor provides relevant information about a given error code.
type ErrorDescriptor struct {
// Code is the error code that this descriptor describes.
Code ErrorCode
// Value provides a unique, string key, often captilized with
// underscores, to identify the error code. This value is used as the
// keyed value when serializing api errors.
Value string
// Message is a short, human readable decription of the error condition
// included in API responses.
Message string
// Description provides a complete account of the errors purpose, suitable
// for use in documentation.
Description string
// HTTPStatusCode provides the http status code that is associated with
// this error condition.
HTTPStatusCode int
}
var (
errorCodeToDescriptors = map[ErrorCode]ErrorDescriptor{}
idToDescriptors = map[string]ErrorDescriptor{}
)
const (
// ErrorCodeUnknown is a catch-all for errors not defined below.
ErrorCodeUnknown ErrorCode = 10000 + iota
)
var errorDescriptors = []ErrorDescriptor{
{
Code: ErrorCodeUnknown,
Value: "UNKNOWN",
Message: "unknown error",
Description: `Generic error returned when the error does not have an
API classification.`,
HTTPStatusCode: http.StatusInternalServerError,
},
}
// LoadErrors will register a new set of Errors into the system
func LoadErrors(errs *[]ErrorDescriptor) {
for _, descriptor := range *errs {
if _, ok := idToDescriptors[descriptor.Value]; ok {
panic(fmt.Sprintf("ErrorValue %s is already registered", descriptor.Value))
}
if _, ok := errorCodeToDescriptors[descriptor.Code]; ok {
panic(fmt.Sprintf("ErrorCode %d is already registered", descriptor.Code))
}
errorCodeToDescriptors[descriptor.Code] = descriptor
idToDescriptors[descriptor.Value] = descriptor
}
}
// ParseErrorCode attempts to parse the error code string, returning
// ErrorCodeUnknown if the error is not known.
func ParseErrorCode(s string) ErrorCode {
desc, ok := idToDescriptors[s]
if !ok {
return ErrorCodeUnknown
}
return desc.Code
}
// Descriptor returns the descriptor for the error code.
func (ec ErrorCode) Descriptor() ErrorDescriptor {
d, ok := errorCodeToDescriptors[ec]
if !ok {
return ErrorCodeUnknown.Descriptor()
}
return d
}
// String returns the canonical identifier for this error code.
func (ec ErrorCode) String() string {
return ec.Descriptor().Value
}
// Message returned the human-readable error message for this error code.
func (ec ErrorCode) Message() string {
return ec.Descriptor().Message
}
// MarshalText encodes the receiver into UTF-8-encoded text and returns the
// result.
func (ec ErrorCode) MarshalText() (text []byte, err error) {
return []byte(ec.String()), nil
}
// UnmarshalText decodes the form generated by MarshalText.
func (ec *ErrorCode) UnmarshalText(text []byte) error {
desc, ok := idToDescriptors[string(text)]
if !ok {
desc = ErrorCodeUnknown.Descriptor()
}
*ec = desc.Code
return nil
}
// Error provides a wrapper around ErrorCode with extra Details provided.
type Error struct {
Code ErrorCode `json:"code"`
Message string `json:"message,omitempty"`
Detail interface{} `json:"detail,omitempty"`
}
// Error returns a human readable representation of the error.
func (e Error) Error() string {
return fmt.Sprintf("%s: %s",
strings.ToLower(strings.Replace(e.Code.String(), "_", " ", -1)),
e.Message)
}
// Errors provides the envelope for multiple errors and a few sugar methods
// for use within the application.
type Errors struct {
Errors []Error `json:"errors,omitempty"`
}
// Push pushes an error on to the error stack, with the optional detail
// argument. It is a programming error (ie panic) to push more than one
// detail at a time.
func (errs *Errors) Push(code ErrorCode, details ...interface{}) {
if len(details) > 1 {
panic("please specify zero or one detail items for this error")
}
var detail interface{}
if len(details) > 0 {
detail = details[0]
}
if err, ok := detail.(error); ok {
detail = err.Error()
}
errs.PushErr(Error{
Code: code,
Message: code.Message(),
Detail: detail,
})
}
// PushErr pushes an error interface onto the error stack.
func (errs *Errors) PushErr(err error) {
switch err.(type) {
case Error:
errs.Errors = append(errs.Errors, err.(Error))
default:
errs.Errors = append(errs.Errors, Error{Message: err.Error()})
}
}
func (errs *Errors) Error() string {
switch errs.Len() {
case 0:
return "<nil>"
case 1:
return errs.Errors[0].Error()
default:
msg := "errors:\n"
for _, err := range errs.Errors {
msg += err.Error() + "\n"
}
return msg
}
}
// Clear clears the errors.
func (errs *Errors) Clear() {
errs.Errors = nil
}
// Len returns the current number of errors.
func (errs *Errors) Len() int {
return len(errs.Errors)
}
// init loads the default errors that are part of the errcode package
func init() {
LoadErrors(&errorDescriptors)
}