Merge pull request #548 from duglin/MoveErrors

Move ErrorCode logic to new errcode package
2015-06-15 14:33:28 -07:00 · 2015-06-15 14:33:28 -07:00 · 728ca4b391
commit 728ca4b391
parent 280b9c50ac 56349665b7
18 changed files with 746 additions and 652 deletions
--- a/docs/api/errcode/errors.go
+++ b/docs/api/errcode/errors.go
@ -0,0 +1,225 @@
+package errcode
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// ErrorCoder is the base interface for ErrorCode and Error allowing
+// users of each to just call ErrorCode to get the real ID of each
+type ErrorCoder interface {
+	ErrorCode() ErrorCode
+}
+
+// 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
+
+// ErrorCode just returns itself
+func (ec ErrorCode) ErrorCode() ErrorCode {
+	return ec
+}
+
+// Error returns the ID/Value
+func (ec ErrorCode) Error() string {
+	return ec.Descriptor().Value
+}
+
+// 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
+}
+
+// WithDetail creates a new Error struct based on the passed-in info and
+// set the Detail property appropriately
+func (ec ErrorCode) WithDetail(detail interface{}) Error {
+	if err, ok := detail.(error); ok {
+		detail = err.Error()
+	}
+
+	return Error{
+		Code:   ec,
+		Detail: detail,
+	}
+}
+
+// Error provides a wrapper around ErrorCode with extra Details provided.
+type Error struct {
+	Code   ErrorCode   `json:"code"`
+	Detail interface{} `json:"detail,omitempty"`
+}
+
+// ErrorCode returns the ID/Value of this Error
+func (e Error) ErrorCode() ErrorCode {
+	return e.Code
+}
+
+// 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.Code.Message())
+}
+
+// Message returned the human-readable error message for this Error
+func (e Error) Message() string {
+	return e.Code.Message()
+}
+
+// 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
+}
+
+// ParseErrorCode returns the value by the string error code.
+// `ErrorCodeUnknown` will be returned if the error is not known.
+func ParseErrorCode(value string) ErrorCode {
+	ed, ok := idToDescriptors[value]
+	if ok {
+		return ed.Code
+	}
+
+	return ErrorCodeUnknown
+}
+
+// Errors provides the envelope for multiple errors and a few sugar methods
+// for use within the application.
+type Errors []error
+
+func (errs Errors) Error() string {
+	switch len(errs) {
+	case 0:
+		return "<nil>"
+	case 1:
+		return errs[0].Error()
+	default:
+		msg := "errors:\n"
+		for _, err := range errs {
+			msg += err.Error() + "\n"
+		}
+		return msg
+	}
+}
+
+// Len returns the current number of errors.
+func (errs Errors) Len() int {
+	return len(errs)
+}
+
+// jsonError extends Error with 'Message' so that we can include the
+// error text, just in case the receiver of the JSON doesn't have this
+// particular ErrorCode registered
+type jsonError struct {
+	Code    ErrorCode   `json:"code"`
+	Message string      `json:"message"`
+	Detail  interface{} `json:"detail,omitempty"`
+}
+
+// MarshalJSON converts slice of error, ErrorCode or Error into a
+// slice of Error - then serializes
+func (errs Errors) MarshalJSON() ([]byte, error) {
+	var tmpErrs []jsonError
+
+	for _, daErr := range errs {
+		var err Error
+
+		switch daErr.(type) {
+		case ErrorCode:
+			err = daErr.(ErrorCode).WithDetail(nil)
+		case Error:
+			err = daErr.(Error)
+		default:
+			err = ErrorCodeUnknown.WithDetail(daErr)
+
+		}
+
+		tmpErrs = append(tmpErrs, jsonError{
+			Code:    err.Code,
+			Message: err.Message(),
+			Detail:  err.Detail,
+		})
+	}
+
+	return json.Marshal(tmpErrs)
+}
+
+// UnmarshalJSON deserializes []Error and then converts it into slice of
+// Error or ErrorCode
+func (errs *Errors) UnmarshalJSON(data []byte) error {
+	var tmpErrs []jsonError
+
+	if err := json.Unmarshal(data, &tmpErrs); err != nil {
+		return err
+	}
+
+	var newErrs Errors
+	for _, daErr := range tmpErrs {
+		if daErr.Detail == nil {
+			// Error's w/o details get converted to ErrorCode
+			newErrs = append(newErrs, daErr.Code)
+		} else {
+			// Error's w/ details are untouched
+			newErrs = append(newErrs, Error{
+				Code:   daErr.Code,
+				Detail: daErr.Detail,
+			})
+		}
+	}
+
+	*errs = newErrs
+	return nil
+}
--- a/docs/api/errcode/errors_test.go
+++ b/docs/api/errcode/errors_test.go
@ -0,0 +1,131 @@
+package errcode
+
+import (
+	"encoding/json"
+	"net/http"
+	"reflect"
+	"testing"
+)
+
+// TestErrorCodes ensures that error code format, mappings and
+// marshaling/unmarshaling. round trips are stable.
+func TestErrorCodes(t *testing.T) {
+	if len(errorCodeToDescriptors) == 0 {
+		t.Fatal("errors aren't loaded!")
+	}
+
+	for ec, desc := range errorCodeToDescriptors {
+		if ec != desc.Code {
+			t.Fatalf("error code in descriptor isn't correct, %q != %q", ec, desc.Code)
+		}
+
+		if idToDescriptors[desc.Value].Code != ec {
+			t.Fatalf("error code in idToDesc isn't correct, %q != %q", idToDescriptors[desc.Value].Code, ec)
+		}
+
+		if ec.Message() != desc.Message {
+			t.Fatalf("ec.Message doesn't mtach desc.Message: %q != %q", ec.Message(), desc.Message)
+		}
+
+		// Test (de)serializing the ErrorCode
+		p, err := json.Marshal(ec)
+		if err != nil {
+			t.Fatalf("couldn't marshal ec %v: %v", ec, err)
+		}
+
+		if len(p) <= 0 {
+			t.Fatalf("expected content in marshaled before for error code %v", ec)
+		}
+
+		// First, unmarshal to interface and ensure we have a string.
+		var ecUnspecified interface{}
+		if err := json.Unmarshal(p, &ecUnspecified); err != nil {
+			t.Fatalf("error unmarshaling error code %v: %v", ec, err)
+		}
+
+		if _, ok := ecUnspecified.(string); !ok {
+			t.Fatalf("expected a string for error code %v on unmarshal got a %T", ec, ecUnspecified)
+		}
+
+		// Now, unmarshal with the error code type and ensure they are equal
+		var ecUnmarshaled ErrorCode
+		if err := json.Unmarshal(p, &ecUnmarshaled); err != nil {
+			t.Fatalf("error unmarshaling error code %v: %v", ec, err)
+		}
+
+		if ecUnmarshaled != ec {
+			t.Fatalf("unexpected error code during error code marshal/unmarshal: %v != %v", ecUnmarshaled, ec)
+		}
+	}
+
+}
+
+// TestErrorsManagement does a quick check of the Errors type to ensure that
+// members are properly pushed and marshaled.
+var ErrorCodeTest1 = Register("v2.errors", ErrorDescriptor{
+	Value:          "TEST1",
+	Message:        "test error 1",
+	Description:    `Just a test message #1.`,
+	HTTPStatusCode: http.StatusInternalServerError,
+})
+
+var ErrorCodeTest2 = Register("v2.errors", ErrorDescriptor{
+	Value:          "TEST2",
+	Message:        "test error 2",
+	Description:    `Just a test message #2.`,
+	HTTPStatusCode: http.StatusNotFound,
+})
+
+func TestErrorsManagement(t *testing.T) {
+	var errs Errors
+
+	errs = append(errs, ErrorCodeTest1)
+	errs = append(errs, ErrorCodeTest2.WithDetail(
+		map[string]interface{}{"digest": "sometestblobsumdoesntmatter"}))
+
+	p, err := json.Marshal(errs)
+
+	if err != nil {
+		t.Fatalf("error marashaling errors: %v", err)
+	}
+
+	expectedJSON := "[{\"code\":\"TEST1\",\"message\":\"test error 1\"},{\"code\":\"TEST2\",\"message\":\"test error 2\",\"detail\":{\"digest\":\"sometestblobsumdoesntmatter\"}}]"
+
+	if string(p) != expectedJSON {
+		t.Fatalf("unexpected json:\ngot:\n%q\n\nexpected:\n%q", string(p), expectedJSON)
+	}
+
+	// Now test the reverse
+	var unmarshaled Errors
+	if err := json.Unmarshal(p, &unmarshaled); err != nil {
+		t.Fatalf("unexpected error unmarshaling error envelope: %v", err)
+	}
+
+	if !reflect.DeepEqual(unmarshaled, errs) {
+		t.Fatalf("errors not equal after round trip:\nunmarshaled:\n%#v\n\nerrs:\n%#v", unmarshaled, errs)
+	}
+
+	// Test again with a single value this time
+	errs = Errors{ErrorCodeUnknown}
+	expectedJSON = "[{\"code\":\"UNKNOWN\",\"message\":\"unknown error\"}]"
+	p, err = json.Marshal(errs)
+
+	if err != nil {
+		t.Fatalf("error marashaling errors: %v", err)
+	}
+
+	if string(p) != expectedJSON {
+		t.Fatalf("unexpected json: %q != %q", string(p), expectedJSON)
+	}
+
+	// Now test the reverse
+	unmarshaled = nil
+	if err := json.Unmarshal(p, &unmarshaled); err != nil {
+		t.Fatalf("unexpected error unmarshaling error envelope: %v", err)
+	}
+
+	if !reflect.DeepEqual(unmarshaled, errs) {
+		t.Fatalf("errors not equal after round trip:\nunmarshaled:\n%#v\n\nerrs:\n%#v", unmarshaled, errs)
+	}
+
+}
--- a/docs/api/errcode/register.go
+++ b/docs/api/errcode/register.go
@ -0,0 +1,86 @@
+package errcode
+
+import (
+	"fmt"
+	"net/http"
+	"sort"
+	"sync"
+)
+
+var (
+	errorCodeToDescriptors = map[ErrorCode]ErrorDescriptor{}
+	idToDescriptors        = map[string]ErrorDescriptor{}
+	groupToDescriptors     = map[string][]ErrorDescriptor{}
+)
+
+// ErrorCodeUnknown is a generic error that can be used as a last
+// resort if there is no situation-specific error message that can be used
+var ErrorCodeUnknown = Register("errcode", ErrorDescriptor{
+	Value:   "UNKNOWN",
+	Message: "unknown error",
+	Description: `Generic error returned when the error does not have an
+			                                            API classification.`,
+	HTTPStatusCode: http.StatusInternalServerError,
+})
+
+var nextCode = 1000
+var registerLock sync.Mutex
+
+// Register will make the passed-in error known to the environment and
+// return a new ErrorCode
+func Register(group string, descriptor ErrorDescriptor) ErrorCode {
+	registerLock.Lock()
+	defer registerLock.Unlock()
+
+	descriptor.Code = ErrorCode(nextCode)
+
+	if _, ok := idToDescriptors[descriptor.Value]; ok {
+		panic(fmt.Sprintf("ErrorValue %q is already registered", descriptor.Value))
+	}
+	if _, ok := errorCodeToDescriptors[descriptor.Code]; ok {
+		panic(fmt.Sprintf("ErrorCode %v is already registered", descriptor.Code))
+	}
+
+	groupToDescriptors[group] = append(groupToDescriptors[group], descriptor)
+	errorCodeToDescriptors[descriptor.Code] = descriptor
+	idToDescriptors[descriptor.Value] = descriptor
+
+	nextCode++
+	return descriptor.Code
+}
+
+type byValue []ErrorDescriptor
+
+func (a byValue) Len() int           { return len(a) }
+func (a byValue) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a byValue) Less(i, j int) bool { return a[i].Value < a[j].Value }
+
+// GetGroupNames returns the list of Error group names that are registered
+func GetGroupNames() []string {
+	keys := []string{}
+
+	for k := range groupToDescriptors {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
+// GetErrorCodeGroup returns the named group of error descriptors
+func GetErrorCodeGroup(name string) []ErrorDescriptor {
+	desc := groupToDescriptors[name]
+	sort.Sort(byValue(desc))
+	return desc
+}
+
+// GetErrorAllDescriptors returns a slice of all ErrorDescriptors that are
+// registered, irrespective of what group they're in
+func GetErrorAllDescriptors() []ErrorDescriptor {
+	result := []ErrorDescriptor{}
+
+	for _, group := range GetGroupNames() {
+		result = append(result, GetErrorCodeGroup(group)...)
+	}
+	sort.Sort(byValue(result))
+	return result
+}
--- a/docs/api/v2/descriptors.go
+++ b/docs/api/v2/descriptors.go
@ -5,6 +5,7 @@ import (
 	"regexp"

 	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/registry/api/errcode"
 )

 var (
@ -98,7 +99,7 @@ var (
 				Format:      "<length>",
 			},
 		},
-		ErrorCodes: []ErrorCode{
+		ErrorCodes: []errcode.ErrorCode{
 			ErrorCodeUnauthorized,
 		},
 		Body: BodyDescriptor{
@ -119,7 +120,7 @@ var (
 				Format:      "<length>",
 			},
 		},
-		ErrorCodes: []ErrorCode{
+		ErrorCodes: []errcode.ErrorCode{
 			ErrorCodeUnauthorized,
 		},
 		Body: BodyDescriptor{
@ -171,13 +172,8 @@ const (
 var APIDescriptor = struct {
 	// RouteDescriptors provides a list of the routes available in the API.
 	RouteDescriptors []RouteDescriptor
-
-	// ErrorDescriptors provides a list of the error codes and their
-	// associated documentation and metadata.
-	ErrorDescriptors []ErrorDescriptor
 }{
 	RouteDescriptors: routeDescriptors,
-	ErrorDescriptors: errorDescriptors,
 }

 // RouteDescriptor describes a route specified by name.
@ -275,7 +271,7 @@ type ResponseDescriptor struct {

 	// ErrorCodes enumerates the error codes that may be returned along with
 	// the response.
-	ErrorCodes []ErrorCode
+	ErrorCodes []errcode.ErrorCode

 	// Body describes the body of the response, if any.
 	Body BodyDescriptor
@ -317,30 +313,6 @@ type ParameterDescriptor struct {
 	Examples []string
 }

-// 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
-
-	// HTTPStatusCodes provides a list of status under which this error
-	// condition may arise. If it is empty, the error condition may be seen
-	// for any status code.
-	HTTPStatusCodes []int
-}
-
 var routeDescriptors = []RouteDescriptor{
 	{
 		Name:        RouteNameBase,
@ -374,7 +346,7 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeUnauthorized,
 								},
 							},
@ -438,7 +410,7 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameUnknown,
 								},
 							},
@ -449,7 +421,7 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeUnauthorized,
 								},
 							},
@ -495,7 +467,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "The name or reference was invalid.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameInvalid,
 									ErrorCodeTagInvalid,
 								},
@ -511,14 +483,14 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeUnauthorized,
 								},
 							},
 							{
 								Description: "The named manifest is not known to the registry.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameUnknown,
 									ErrorCodeManifestUnknown,
 								},
@ -573,7 +545,7 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameInvalid,
 									ErrorCodeTagInvalid,
 									ErrorCodeManifestInvalid,
@ -588,7 +560,7 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeUnauthorized,
 								},
 							},
@ -596,7 +568,7 @@ var routeDescriptors = []RouteDescriptor{
 								Name:        "Missing Layer(s)",
 								Description: "One or more layers may be missing during a manifest upload. If so, the missing layers will be enumerated in the error response.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeBlobUnknown,
 								},
 								Body: BodyDescriptor{
@ -625,7 +597,7 @@ var routeDescriptors = []RouteDescriptor{
 										Format:      "<length>",
 									},
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeUnauthorized,
 								},
 								Body: BodyDescriptor{
@ -660,7 +632,7 @@ var routeDescriptors = []RouteDescriptor{
 								Name:        "Invalid Name or Reference",
 								Description: "The specified `name` or `reference` were invalid and the delete was unable to proceed.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameInvalid,
 									ErrorCodeTagInvalid,
 								},
@ -680,7 +652,7 @@ var routeDescriptors = []RouteDescriptor{
 										Format:      "<length>",
 									},
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeUnauthorized,
 								},
 								Body: BodyDescriptor{
@ -692,7 +664,7 @@ var routeDescriptors = []RouteDescriptor{
 								Name:        "Unknown Manifest",
 								Description: "The specified `name` or `reference` are unknown to the registry and the delete was unable to proceed. Clients can assume the manifest was already deleted if this response is returned.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameUnknown,
 									ErrorCodeManifestUnknown,
 								},
@ -765,7 +737,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "There was a problem with the request that needs to be addressed by the client, such as an invalid `name` or `tag`.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameInvalid,
 									ErrorCodeDigestInvalid,
 								},
@ -782,7 +754,7 @@ var routeDescriptors = []RouteDescriptor{
 									ContentType: "application/json; charset=utf-8",
 									Format:      errorsBody,
 								},
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameUnknown,
 									ErrorCodeBlobUnknown,
 								},
@ -834,7 +806,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "There was a problem with the request that needs to be addressed by the client, such as an invalid `name` or `tag`.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameInvalid,
 									ErrorCodeDigestInvalid,
 								},
@ -846,7 +818,7 @@ var routeDescriptors = []RouteDescriptor{
 							unauthorizedResponse,
 							{
 								StatusCode: http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameUnknown,
 									ErrorCodeBlobUnknown,
 								},
@ -926,7 +898,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Name:       "Invalid Name or Digest",
 								StatusCode: http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeDigestInvalid,
 									ErrorCodeNameInvalid,
 								},
@ -970,7 +942,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Name:       "Invalid Name or Digest",
 								StatusCode: http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeDigestInvalid,
 									ErrorCodeNameInvalid,
 								},
@ -1024,7 +996,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "There was an error processing the upload and it must be restarted.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeDigestInvalid,
 									ErrorCodeNameInvalid,
 									ErrorCodeBlobUploadInvalid,
@ -1038,7 +1010,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "The upload is unknown to the registry. The upload must be restarted.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeBlobUploadUnknown,
 								},
 								Body: BodyDescriptor{
@ -1096,7 +1068,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "There was an error processing the upload and it must be restarted.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeDigestInvalid,
 									ErrorCodeNameInvalid,
 									ErrorCodeBlobUploadInvalid,
@ -1110,7 +1082,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "The upload is unknown to the registry. The upload must be restarted.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeBlobUploadUnknown,
 								},
 								Body: BodyDescriptor{
@ -1175,7 +1147,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "There was an error processing the upload and it must be restarted.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeDigestInvalid,
 									ErrorCodeNameInvalid,
 									ErrorCodeBlobUploadInvalid,
@ -1189,7 +1161,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "The upload is unknown to the registry. The upload must be restarted.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeBlobUploadUnknown,
 								},
 								Body: BodyDescriptor{
@ -1266,7 +1238,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "There was an error processing the upload and it must be restarted.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeDigestInvalid,
 									ErrorCodeNameInvalid,
 									ErrorCodeBlobUploadInvalid,
@ -1280,7 +1252,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "The upload is unknown to the registry. The upload must be restarted.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeBlobUploadUnknown,
 								},
 								Body: BodyDescriptor{
@ -1321,7 +1293,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "An error was encountered processing the delete. The client may ignore this error.",
 								StatusCode:  http.StatusBadRequest,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeNameInvalid,
 									ErrorCodeBlobUploadInvalid,
 								},
@ -1334,7 +1306,7 @@ var routeDescriptors = []RouteDescriptor{
 							{
 								Description: "The upload is unknown to the registry. The client may ignore this error and assume the upload has been deleted.",
 								StatusCode:  http.StatusNotFound,
-								ErrorCodes: []ErrorCode{
+								ErrorCodes: []errcode.ErrorCode{
 									ErrorCodeBlobUploadUnknown,
 								},
 								Body: BodyDescriptor{
@ -1350,143 +1322,11 @@ var routeDescriptors = []RouteDescriptor{
 	},
 }

-// ErrorDescriptors provides a list of HTTP API Error codes that may be
-// encountered when interacting with the registry API.
-var errorDescriptors = []ErrorDescriptor{
-	{
-		Code:    ErrorCodeUnknown,
-		Value:   "UNKNOWN",
-		Message: "unknown error",
-		Description: `Generic error returned when the error does not have an
-		API classification.`,
-	},
-	{
-		Code:    ErrorCodeUnsupported,
-		Value:   "UNSUPPORTED",
-		Message: "The operation is unsupported.",
-		Description: `The operation was unsupported due to a missing
-		implementation or invalid set of parameters.`,
-	},
-	{
-		Code:    ErrorCodeUnauthorized,
-		Value:   "UNAUTHORIZED",
-		Message: "access to the requested resource is not authorized",
-		Description: `The access controller denied access for the operation on
-		a resource. Often this will be accompanied by a 401 Unauthorized
-		response status.`,
-	},
-	{
-		Code:    ErrorCodeDigestInvalid,
-		Value:   "DIGEST_INVALID",
-		Message: "provided digest did not match uploaded content",
-		Description: `When a blob is uploaded, the registry will check that
-		the content matches the digest provided by the client. The error may
-		include a detail structure with the key "digest", including the
-		invalid digest string. This error may also be returned when a manifest
-		includes an invalid layer digest.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest, http.StatusNotFound},
-	},
-	{
-		Code:    ErrorCodeSizeInvalid,
-		Value:   "SIZE_INVALID",
-		Message: "provided length did not match content length",
-		Description: `When a layer is uploaded, the provided size will be
-		checked against the uploaded content. If they do not match, this error
-		will be returned.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest},
-	},
-	{
-		Code:    ErrorCodeNameInvalid,
-		Value:   "NAME_INVALID",
-		Message: "invalid repository name",
-		Description: `Invalid repository name encountered either during
-		manifest validation or any API operation.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest, http.StatusNotFound},
-	},
-	{
-		Code:    ErrorCodeTagInvalid,
-		Value:   "TAG_INVALID",
-		Message: "manifest tag did not match URI",
-		Description: `During a manifest upload, if the tag in the manifest
-		does not match the uri tag, this error will be returned.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest, http.StatusNotFound},
-	},
-	{
-		Code:    ErrorCodeNameUnknown,
-		Value:   "NAME_UNKNOWN",
-		Message: "repository name not known to registry",
-		Description: `This is returned if the name used during an operation is
-		unknown to the registry.`,
-		HTTPStatusCodes: []int{http.StatusNotFound},
-	},
-	{
-		Code:    ErrorCodeManifestUnknown,
-		Value:   "MANIFEST_UNKNOWN",
-		Message: "manifest unknown",
-		Description: `This error is returned when the manifest, identified by
-		name and tag is unknown to the repository.`,
-		HTTPStatusCodes: []int{http.StatusNotFound},
-	},
-	{
-		Code:    ErrorCodeManifestInvalid,
-		Value:   "MANIFEST_INVALID",
-		Message: "manifest invalid",
-		Description: `During upload, manifests undergo several checks ensuring
-		validity. If those checks fail, this error may be returned, unless a
-		more specific error is included. The detail will contain information
-		the failed validation.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest},
-	},
-	{
-		Code:    ErrorCodeManifestUnverified,
-		Value:   "MANIFEST_UNVERIFIED",
-		Message: "manifest failed signature verification",
-		Description: `During manifest upload, if the manifest fails signature
-		verification, this error will be returned.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest},
-	},
-	{
-		Code:    ErrorCodeBlobUnknown,
-		Value:   "BLOB_UNKNOWN",
-		Message: "blob unknown to registry",
-		Description: `This error may be returned when a blob is unknown to the
-		registry in a specified repository. This can be returned with a
-		standard get or if a manifest references an unknown layer during
-		upload.`,
-		HTTPStatusCodes: []int{http.StatusBadRequest, http.StatusNotFound},
-	},
-
-	{
-		Code:    ErrorCodeBlobUploadUnknown,
-		Value:   "BLOB_UPLOAD_UNKNOWN",
-		Message: "blob upload unknown to registry",
-		Description: `If a blob upload has been cancelled or was never
-		started, this error code may be returned.`,
-		HTTPStatusCodes: []int{http.StatusNotFound},
-	},
-	{
-		Code:    ErrorCodeBlobUploadInvalid,
-		Value:   "BLOB_UPLOAD_INVALID",
-		Message: "blob upload invalid",
-		Description: `The blob upload encountered an error and can no
-		longer proceed.`,
-		HTTPStatusCodes: []int{http.StatusNotFound},
-	},
-}
-
-var errorCodeToDescriptors map[ErrorCode]ErrorDescriptor
-var idToDescriptors map[string]ErrorDescriptor
 var routeDescriptorsMap map[string]RouteDescriptor

 func init() {
-	errorCodeToDescriptors = make(map[ErrorCode]ErrorDescriptor, len(errorDescriptors))
-	idToDescriptors = make(map[string]ErrorDescriptor, len(errorDescriptors))
 	routeDescriptorsMap = make(map[string]RouteDescriptor, len(routeDescriptors))

-	for _, descriptor := range errorDescriptors {
-		errorCodeToDescriptors[descriptor.Code] = descriptor
-		idToDescriptors[descriptor.Value] = descriptor
-	}
 	for _, descriptor := range routeDescriptors {
 		routeDescriptorsMap[descriptor.Name] = descriptor
 	}
--- a/docs/api/v2/errors.go
+++ b/docs/api/v2/errors.go
@ -1,194 +1,154 @@
 package v2

 import (
-	"fmt"
-	"strings"
+	"net/http"
+
+	"github.com/docker/distribution/registry/api/errcode"
 )

-// 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
-
-const (
-	// ErrorCodeUnknown is a catch-all for errors not defined below.
-	ErrorCodeUnknown ErrorCode = iota
+const errGroup = "registry.api.v2"

+var (
 	// ErrorCodeUnsupported is returned when an operation is not supported.
-	ErrorCodeUnsupported
+	ErrorCodeUnsupported = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "UNSUPPORTED",
+		Message: "The operation is unsupported.",
+		Description: `The operation was unsupported due to a missing
+		implementation or invalid set of parameters.`,
+	})

 	// ErrorCodeUnauthorized is returned if a request is not authorized.
-	ErrorCodeUnauthorized
+	ErrorCodeUnauthorized = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "UNAUTHORIZED",
+		Message: "access to the requested resource is not authorized",
+		Description: `The access controller denied access for the operation on
+		a resource. Often this will be accompanied by a 401 Unauthorized
+		response status.`,
+		HTTPStatusCode: http.StatusForbidden,
+	})

 	// ErrorCodeDigestInvalid is returned when uploading a blob if the
 	// provided digest does not match the blob contents.
-	ErrorCodeDigestInvalid
+	ErrorCodeDigestInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "DIGEST_INVALID",
+		Message: "provided digest did not match uploaded content",
+		Description: `When a blob is uploaded, the registry will check that
+		the content matches the digest provided by the client. The error may
+		include a detail structure with the key "digest", including the
+		invalid digest string. This error may also be returned when a manifest
+		includes an invalid layer digest.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})

 	// ErrorCodeSizeInvalid is returned when uploading a blob if the provided
-	// size does not match the content length.
-	ErrorCodeSizeInvalid
+	ErrorCodeSizeInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "SIZE_INVALID",
+		Message: "provided length did not match content length",
+		Description: `When a layer is uploaded, the provided size will be
+		checked against the uploaded content. If they do not match, this error
+		will be returned.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})

 	// ErrorCodeNameInvalid is returned when the name in the manifest does not
 	// match the provided name.
-	ErrorCodeNameInvalid
+	ErrorCodeNameInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "NAME_INVALID",
+		Message: "invalid repository name",
+		Description: `Invalid repository name encountered either during
+		manifest validation or any API operation.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})

 	// ErrorCodeTagInvalid is returned when the tag in the manifest does not
 	// match the provided tag.
-	ErrorCodeTagInvalid
+	ErrorCodeTagInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "TAG_INVALID",
+		Message: "manifest tag did not match URI",
+		Description: `During a manifest upload, if the tag in the manifest
+		does not match the uri tag, this error will be returned.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})

 	// ErrorCodeNameUnknown when the repository name is not known.
-	ErrorCodeNameUnknown
+	ErrorCodeNameUnknown = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "NAME_UNKNOWN",
+		Message: "repository name not known to registry",
+		Description: `This is returned if the name used during an operation is
+		unknown to the registry.`,
+		HTTPStatusCode: http.StatusNotFound,
+	})

 	// ErrorCodeManifestUnknown returned when image manifest is unknown.
-	ErrorCodeManifestUnknown
+	ErrorCodeManifestUnknown = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "MANIFEST_UNKNOWN",
+		Message: "manifest unknown",
+		Description: `This error is returned when the manifest, identified by
+		name and tag is unknown to the repository.`,
+		HTTPStatusCode: http.StatusNotFound,
+	})

 	// ErrorCodeManifestInvalid returned when an image manifest is invalid,
 	// typically during a PUT operation. This error encompasses all errors
 	// encountered during manifest validation that aren't signature errors.
-	ErrorCodeManifestInvalid
+	ErrorCodeManifestInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "MANIFEST_INVALID",
+		Message: "manifest invalid",
+		Description: `During upload, manifests undergo several checks ensuring
+		validity. If those checks fail, this error may be returned, unless a
+		more specific error is included. The detail will contain information
+		the failed validation.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})

 	// ErrorCodeManifestUnverified is returned when the manifest fails
 	// signature verfication.
-	ErrorCodeManifestUnverified
+	ErrorCodeManifestUnverified = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "MANIFEST_UNVERIFIED",
+		Message: "manifest failed signature verification",
+		Description: `During manifest upload, if the manifest fails signature
+		verification, this error will be returned.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})
+
+	// ErrorCodeManifestBlobUnknown is returned when a manifest blob is
+	// unknown to the registry.
+	ErrorCodeManifestBlobUnknown = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "MANIFEST_BLOB_UNKNOWN",
+		Message: "blob unknown to registry",
+		Description: `This error may be returned when a manifest blob is 
+		unknown to the registry.`,
+		HTTPStatusCode: http.StatusBadRequest,
+	})

 	// ErrorCodeBlobUnknown is returned when a blob is unknown to the
 	// registry. This can happen when the manifest references a nonexistent
 	// layer or the result is not found by a blob fetch.
-	ErrorCodeBlobUnknown
+	ErrorCodeBlobUnknown = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "BLOB_UNKNOWN",
+		Message: "blob unknown to registry",
+		Description: `This error may be returned when a blob is unknown to the
+		registry in a specified repository. This can be returned with a
+		standard get or if a manifest references an unknown layer during
+		upload.`,
+		HTTPStatusCode: http.StatusNotFound,
+	})

 	// ErrorCodeBlobUploadUnknown is returned when an upload is unknown.
-	ErrorCodeBlobUploadUnknown
+	ErrorCodeBlobUploadUnknown = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "BLOB_UPLOAD_UNKNOWN",
+		Message: "blob upload unknown to registry",
+		Description: `If a blob upload has been cancelled or was never
+		started, this error code may be returned.`,
+		HTTPStatusCode: http.StatusNotFound,
+	})

 	// ErrorCodeBlobUploadInvalid is returned when an upload is invalid.
-	ErrorCodeBlobUploadInvalid
-)
-
-// 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,
+	ErrorCodeBlobUploadInvalid = errcode.Register(errGroup, errcode.ErrorDescriptor{
+		Value:   "BLOB_UPLOAD_INVALID",
+		Message: "blob upload invalid",
+		Description: `The blob upload encountered an error and can no
+		longer proceed.`,
+		HTTPStatusCode: http.StatusNotFound,
 	})
-}
-
-// 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 = errs.Errors[:0]
-}
-
-// Len returns the current number of errors.
-func (errs *Errors) Len() int {
-	return len(errs.Errors)
-}
+)
--- a/docs/api/v2/errors_test.go
+++ b/docs/api/v2/errors_test.go
@ -1,165 +0,0 @@
-package v2
-
-import (
-	"encoding/json"
-	"reflect"
-	"testing"
-
-	"github.com/docker/distribution/digest"
-)
-
-// TestErrorCodes ensures that error code format, mappings and
-// marshaling/unmarshaling. round trips are stable.
-func TestErrorCodes(t *testing.T) {
-	for _, desc := range errorDescriptors {
-		if desc.Code.String() != desc.Value {
-			t.Fatalf("error code string incorrect: %q != %q", desc.Code.String(), desc.Value)
-		}
-
-		if desc.Code.Message() != desc.Message {
-			t.Fatalf("incorrect message for error code %v: %q != %q", desc.Code, desc.Code.Message(), desc.Message)
-		}
-
-		// Serialize the error code using the json library to ensure that we
-		// get a string and it works round trip.
-		p, err := json.Marshal(desc.Code)
-
-		if err != nil {
-			t.Fatalf("error marshaling error code %v: %v", desc.Code, err)
-		}
-
-		if len(p) <= 0 {
-			t.Fatalf("expected content in marshaled before for error code %v", desc.Code)
-		}
-
-		// First, unmarshal to interface and ensure we have a string.
-		var ecUnspecified interface{}
-		if err := json.Unmarshal(p, &ecUnspecified); err != nil {
-			t.Fatalf("error unmarshaling error code %v: %v", desc.Code, err)
-		}
-
-		if _, ok := ecUnspecified.(string); !ok {
-			t.Fatalf("expected a string for error code %v on unmarshal got a %T", desc.Code, ecUnspecified)
-		}
-
-		// Now, unmarshal with the error code type and ensure they are equal
-		var ecUnmarshaled ErrorCode
-		if err := json.Unmarshal(p, &ecUnmarshaled); err != nil {
-			t.Fatalf("error unmarshaling error code %v: %v", desc.Code, err)
-		}
-
-		if ecUnmarshaled != desc.Code {
-			t.Fatalf("unexpected error code during error code marshal/unmarshal: %v != %v", ecUnmarshaled, desc.Code)
-		}
-	}
-}
-
-// TestErrorsManagement does a quick check of the Errors type to ensure that
-// members are properly pushed and marshaled.
-func TestErrorsManagement(t *testing.T) {
-	var errs Errors
-
-	errs.Push(ErrorCodeDigestInvalid)
-	errs.Push(ErrorCodeBlobUnknown,
-		map[string]digest.Digest{"digest": "sometestblobsumdoesntmatter"})
-
-	p, err := json.Marshal(errs)
-
-	if err != nil {
-		t.Fatalf("error marashaling errors: %v", err)
-	}
-
-	expectedJSON := "{\"errors\":[{\"code\":\"DIGEST_INVALID\",\"message\":\"provided digest did not match uploaded content\"},{\"code\":\"BLOB_UNKNOWN\",\"message\":\"blob unknown to registry\",\"detail\":{\"digest\":\"sometestblobsumdoesntmatter\"}}]}"
-
-	if string(p) != expectedJSON {
-		t.Fatalf("unexpected json: %q != %q", string(p), expectedJSON)
-	}
-
-	errs.Clear()
-	errs.Push(ErrorCodeUnknown)
-	expectedJSON = "{\"errors\":[{\"code\":\"UNKNOWN\",\"message\":\"unknown error\"}]}"
-	p, err = json.Marshal(errs)
-
-	if err != nil {
-		t.Fatalf("error marashaling errors: %v", err)
-	}
-
-	if string(p) != expectedJSON {
-		t.Fatalf("unexpected json: %q != %q", string(p), expectedJSON)
-	}
-}
-
-// TestMarshalUnmarshal ensures that api errors can round trip through json
-// without losing information.
-func TestMarshalUnmarshal(t *testing.T) {
-
-	var errors Errors
-
-	for _, testcase := range []struct {
-		description string
-		err         Error
-	}{
-		{
-			description: "unknown error",
-			err: Error{
-
-				Code:    ErrorCodeUnknown,
-				Message: ErrorCodeUnknown.Descriptor().Message,
-			},
-		},
-		{
-			description: "unknown manifest",
-			err: Error{
-				Code:    ErrorCodeManifestUnknown,
-				Message: ErrorCodeManifestUnknown.Descriptor().Message,
-			},
-		},
-		{
-			description: "unknown manifest",
-			err: Error{
-				Code:    ErrorCodeBlobUnknown,
-				Message: ErrorCodeBlobUnknown.Descriptor().Message,
-				Detail:  map[string]interface{}{"digest": "asdfqwerqwerqwerqwer"},
-			},
-		},
-	} {
-		fatalf := func(format string, args ...interface{}) {
-			t.Fatalf(testcase.description+": "+format, args...)
-		}
-
-		unexpectedErr := func(err error) {
-			fatalf("unexpected error: %v", err)
-		}
-
-		p, err := json.Marshal(testcase.err)
-		if err != nil {
-			unexpectedErr(err)
-		}
-
-		var unmarshaled Error
-		if err := json.Unmarshal(p, &unmarshaled); err != nil {
-			unexpectedErr(err)
-		}
-
-		if !reflect.DeepEqual(unmarshaled, testcase.err) {
-			fatalf("errors not equal after round trip: %#v != %#v", unmarshaled, testcase.err)
-		}
-
-		// Roll everything up into an error response envelope.
-		errors.PushErr(testcase.err)
-	}
-
-	p, err := json.Marshal(errors)
-	if err != nil {
-		t.Fatalf("unexpected error marshaling error envelope: %v", err)
-	}
-
-	var unmarshaled Errors
-	if err := json.Unmarshal(p, &unmarshaled); err != nil {
-		t.Fatalf("unexpected error unmarshaling error envelope: %v", err)
-	}
-
-	if !reflect.DeepEqual(unmarshaled, errors) {
-		t.Fatalf("errors not equal after round trip: %#v != %#v", unmarshaled, errors)
-	}
-}
--- a/docs/client/blob_writer_test.go
+++ b/docs/client/blob_writer_test.go
@ -7,6 +7,7 @@ import (
 	"testing"

 	"github.com/docker/distribution"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/testutil"
 )
@ -85,15 +86,12 @@ func TestUploadReadFrom(t *testing.T) {
 			Response: testutil.Response{
 				StatusCode: http.StatusBadRequest,
 				Body: []byte(`
-				{
-					"errors": [
+					[
 						{
 							"code": "BLOB_UPLOAD_INVALID",
-							"message": "invalid upload identifier",
 							"detail": "more detail"
 						}
-					]
-				}`),
+					] `),
 			},
 		},
 		// Test 400 invalid json
@ -161,17 +159,20 @@ func TestUploadReadFrom(t *testing.T) {
 	if err == nil {
 		t.Fatalf("Expected error when not found")
 	}
-	if uploadErr, ok := err.(*v2.Errors); !ok {
+	if uploadErr, ok := err.(errcode.Errors); !ok {
 		t.Fatalf("Wrong error type %T: %s", err, err)
-	} else if len(uploadErr.Errors) != 1 {
-		t.Fatalf("Unexpected number of errors: %d, expected 1", len(uploadErr.Errors))
+	} else if len(uploadErr) != 1 {
+		t.Fatalf("Unexpected number of errors: %d, expected 1", len(uploadErr))
 	} else {
-		v2Err := uploadErr.Errors[0]
-		if v2Err.Code != v2.ErrorCodeBlobUploadInvalid {
-			t.Fatalf("Unexpected error code: %s, expected %s", v2Err.Code.String(), v2.ErrorCodeBlobUploadInvalid.String())
+		v2Err, ok := uploadErr[0].(errcode.Error)
+		if !ok {
+			t.Fatalf("Not an 'Error' type: %#v", uploadErr[0])
 		}
-		if expected := "invalid upload identifier"; v2Err.Message != expected {
-			t.Fatalf("Unexpected error message: %s, expected %s", v2Err.Message, expected)
+		if v2Err.Code != v2.ErrorCodeBlobUploadInvalid {
+			t.Fatalf("Unexpected error code: %s, expected %d", v2Err.Code.String(), v2.ErrorCodeBlobUploadInvalid)
+		}
+		if expected := "blob upload invalid"; v2Err.Message() != expected {
+			t.Fatalf("Unexpected error message: %s, expected %s", v2Err.Message(), expected)
 		}
 		if expected := "more detail"; v2Err.Detail.(string) != expected {
 			t.Fatalf("Unexpected error message: %s, expected %s", v2Err.Detail.(string), expected)
--- a/docs/client/errors.go
+++ b/docs/client/errors.go
@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"net/http"

+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 )

@ -32,7 +33,7 @@ func (e *UnexpectedHTTPResponseError) Error() string {
 }

 func parseHTTPErrorResponse(r io.Reader) error {
-	var errors v2.Errors
+	var errors errcode.Errors
 	body, err := ioutil.ReadAll(r)
 	if err != nil {
 		return err
@ -44,17 +45,16 @@ func parseHTTPErrorResponse(r io.Reader) error {
 			Response: body,
 		}
 	}
-	return &errors
+	return errors
 }

 func handleErrorResponse(resp *http.Response) error {
 	if resp.StatusCode == 401 {
 		err := parseHTTPErrorResponse(resp.Body)
 		if uErr, ok := err.(*UnexpectedHTTPResponseError); ok {
-			return &v2.Error{
-				Code:    v2.ErrorCodeUnauthorized,
-				Message: "401 Unauthorized",
-				Detail:  uErr.Response,
+			return &errcode.Error{
+				Code:   v2.ErrorCodeUnauthorized,
+				Detail: uErr.Response,
 			}
 		}
 		return err
--- a/docs/client/repository_test.go
+++ b/docs/client/repository_test.go
@ -18,6 +18,7 @@ import (
 	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
 	"github.com/docker/distribution/manifest"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/testutil"
 )
@ -668,14 +669,14 @@ func TestManifestUnauthorized(t *testing.T) {
 	if err == nil {
 		t.Fatal("Expected error fetching manifest")
 	}
-	v2Err, ok := err.(*v2.Error)
+	v2Err, ok := err.(*errcode.Error)
 	if !ok {
 		t.Fatalf("Unexpected error type: %#v", err)
 	}
 	if v2Err.Code != v2.ErrorCodeUnauthorized {
 		t.Fatalf("Unexpected error code: %s", v2Err.Code.String())
 	}
-	if expected := "401 Unauthorized"; v2Err.Message != expected {
-		t.Fatalf("Unexpected message value: %s, expected %s", v2Err.Message, expected)
+	if expected := errcode.ErrorCode(v2.ErrorCodeUnauthorized).Message(); v2Err.Message() != expected {
+		t.Fatalf("Unexpected message value: %s, expected %s", v2Err.Message(), expected)
 	}
 }
--- a/docs/handlers/api_test.go
+++ b/docs/handlers/api_test.go
@ -19,6 +19,7 @@ import (
 	"github.com/docker/distribution/configuration"
 	"github.com/docker/distribution/digest"
 	"github.com/docker/distribution/manifest"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	_ "github.com/docker/distribution/registry/storage/driver/inmemory"
 	"github.com/docker/distribution/testutil"
@ -373,7 +374,7 @@ func TestManifestAPI(t *testing.T) {
 	_, p, counts := checkBodyHasErrorCodes(t, "getting unknown manifest tags", resp,
 		v2.ErrorCodeManifestUnverified, v2.ErrorCodeBlobUnknown, v2.ErrorCodeDigestInvalid)

-	expectedCounts := map[v2.ErrorCode]int{
+	expectedCounts := map[errcode.ErrorCode]int{
 		v2.ErrorCodeManifestUnverified: 1,
 		v2.ErrorCodeBlobUnknown:        2,
 		v2.ErrorCodeDigestInvalid:      2,
@ -748,18 +749,18 @@ func checkResponse(t *testing.T, msg string, resp *http.Response, expectedStatus
 // checkBodyHasErrorCodes ensures the body is an error body and has the
 // expected error codes, returning the error structure, the json slice and a
 // count of the errors by code.
-func checkBodyHasErrorCodes(t *testing.T, msg string, resp *http.Response, errorCodes ...v2.ErrorCode) (v2.Errors, []byte, map[v2.ErrorCode]int) {
+func checkBodyHasErrorCodes(t *testing.T, msg string, resp *http.Response, errorCodes ...errcode.ErrorCode) (errcode.Errors, []byte, map[errcode.ErrorCode]int) {
 	p, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		t.Fatalf("unexpected error reading body %s: %v", msg, err)
 	}

-	var errs v2.Errors
+	var errs errcode.Errors
 	if err := json.Unmarshal(p, &errs); err != nil {
 		t.Fatalf("unexpected error decoding error response: %v", err)
 	}

-	if len(errs.Errors) == 0 {
+	if len(errs) == 0 {
 		t.Fatalf("expected errors in response")
 	}

@ -770,8 +771,8 @@ func checkBodyHasErrorCodes(t *testing.T, msg string, resp *http.Response, error
 	// 		resp.Header.Get("Content-Type"))
 	// }

-	expected := map[v2.ErrorCode]struct{}{}
-	counts := map[v2.ErrorCode]int{}
+	expected := map[errcode.ErrorCode]struct{}{}
+	counts := map[errcode.ErrorCode]int{}

 	// Initialize map with zeros for expected
 	for _, code := range errorCodes {
@ -779,11 +780,15 @@ func checkBodyHasErrorCodes(t *testing.T, msg string, resp *http.Response, error
 		counts[code] = 0
 	}

-	for _, err := range errs.Errors {
-		if _, ok := expected[err.Code]; !ok {
-			t.Fatalf("unexpected error code %v encountered during %s: %s ", err.Code, msg, string(p))
+	for _, e := range errs {
+		err, ok := e.(errcode.ErrorCoder)
+		if !ok {
+			t.Fatalf("not an ErrorCoder: %#v", e)
 		}
-		counts[err.Code]++
+		if _, ok := expected[err.ErrorCode()]; !ok {
+			t.Fatalf("unexpected error code %v encountered during %s: %s ", err.ErrorCode(), msg, string(p))
+		}
+		counts[err.ErrorCode()]++
 	}

 	// Ensure that counts of expected errors were all non-zero
--- a/docs/handlers/app.go
+++ b/docs/handlers/app.go
@ -14,6 +14,7 @@ import (
 	"github.com/docker/distribution/configuration"
 	ctxu "github.com/docker/distribution/context"
 	"github.com/docker/distribution/notifications"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/auth"
 	registrymiddleware "github.com/docker/distribution/registry/middleware/registry"
@ -372,12 +373,11 @@ func (app *App) dispatcher(dispatch dispatchFunc) http.Handler {

 				switch err := err.(type) {
 				case distribution.ErrRepositoryUnknown:
-					context.Errors.Push(v2.ErrorCodeNameUnknown, err)
+					context.Errors = append(context.Errors, v2.ErrorCodeNameUnknown.WithDetail(err))
 				case distribution.ErrRepositoryNameInvalid:
-					context.Errors.Push(v2.ErrorCodeNameInvalid, err)
+					context.Errors = append(context.Errors, v2.ErrorCodeNameInvalid.WithDetail(err))
 				}

-				w.WriteHeader(http.StatusBadRequest)
 				serveJSON(w, context.Errors)
 				return
 			}
@ -390,8 +390,8 @@ func (app *App) dispatcher(dispatch dispatchFunc) http.Handler {
 			context.Repository, err = applyRepoMiddleware(context.Repository, app.Config.Middleware["repository"])
 			if err != nil {
 				ctxu.GetLogger(context).Errorf("error initializing repository middleware: %v", err)
-				context.Errors.Push(v2.ErrorCodeUnknown, err)
-				w.WriteHeader(http.StatusInternalServerError)
+				context.Errors = append(context.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
+
 				serveJSON(w, context.Errors)
 				return
 			}
@ -402,23 +402,33 @@ func (app *App) dispatcher(dispatch dispatchFunc) http.Handler {
 		// own errors if they need different behavior (such as range errors
 		// for layer upload).
 		if context.Errors.Len() > 0 {
-			if context.Value("http.response.status") == 0 {
-				// TODO(stevvooe): Getting this value from the context is a
-				// bit of a hack. We can further address with some of our
-				// future refactoring.
-				w.WriteHeader(http.StatusBadRequest)
-			}
 			app.logError(context, context.Errors)
+
 			serveJSON(w, context.Errors)
 		}
 	})
 }

-func (app *App) logError(context context.Context, errors v2.Errors) {
-	for _, e := range errors.Errors {
-		c := ctxu.WithValue(context, "err.code", e.Code)
-		c = ctxu.WithValue(c, "err.message", e.Message)
-		c = ctxu.WithValue(c, "err.detail", e.Detail)
+func (app *App) logError(context context.Context, errors errcode.Errors) {
+	for _, e1 := range errors {
+		var c ctxu.Context
+
+		switch e1.(type) {
+		case errcode.Error:
+			e, _ := e1.(errcode.Error)
+			c = ctxu.WithValue(context, "err.code", e.Code)
+			c = ctxu.WithValue(c, "err.message", e.Code.Message())
+			c = ctxu.WithValue(c, "err.detail", e.Detail)
+		case errcode.ErrorCode:
+			e, _ := e1.(errcode.ErrorCode)
+			c = ctxu.WithValue(context, "err.code", e)
+			c = ctxu.WithValue(c, "err.message", e.Message())
+		default:
+			// just normal go 'error'
+			c = ctxu.WithValue(context, "err.code", errcode.ErrorCodeUnknown)
+			c = ctxu.WithValue(c, "err.message", e1.Error())
+		}
+
 		c = ctxu.WithLogger(c, ctxu.GetLogger(c,
 			"err.code",
 			"err.message",
@ -471,11 +481,10 @@ func (app *App) authorized(w http.ResponseWriter, r *http.Request, context *Cont
 			// base route is accessed. This section prevents us from making
 			// that mistake elsewhere in the code, allowing any operation to
 			// proceed.
-			w.Header().Set("Content-Type", "application/json; charset=utf-8")
-			w.WriteHeader(http.StatusForbidden)

-			var errs v2.Errors
-			errs.Push(v2.ErrorCodeUnauthorized)
+			var errs errcode.Errors
+			errs = append(errs, v2.ErrorCodeUnauthorized)
+
 			serveJSON(w, errs)
 			return fmt.Errorf("forbidden: no repository name")
 		}
@ -485,11 +494,20 @@ func (app *App) authorized(w http.ResponseWriter, r *http.Request, context *Cont
 	if err != nil {
 		switch err := err.(type) {
 		case auth.Challenge:
+			// NOTE(duglin):
+			// Since err.ServeHTTP will set the HTTP status code for us
+			// we need to set the content-type here.  The serveJSON
+			// func will try to do it but it'll be too late at that point.
+			// I would have have preferred to just have the auth.Challenge
+			// ServerHTTP func just add the WWW-Authenticate header and let
+			// serveJSON set the HTTP status code and content-type but I wasn't
+			// sure if that's an ok design change. STEVVOOE ?
 			w.Header().Set("Content-Type", "application/json; charset=utf-8")
+
 			err.ServeHTTP(w, r)

-			var errs v2.Errors
-			errs.Push(v2.ErrorCodeUnauthorized, accessRecords)
+			var errs errcode.Errors
+			errs = append(errs, v2.ErrorCodeUnauthorized.WithDetail(accessRecords))
 			serveJSON(w, errs)
 		default:
 			// This condition is a potential security problem either in
--- a/docs/handlers/app_test.go
+++ b/docs/handlers/app_test.go
@ -9,6 +9,7 @@ import (
 	"testing"

 	"github.com/docker/distribution/configuration"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/auth"
 	_ "github.com/docker/distribution/registry/auth/silly"
@ -194,14 +195,18 @@ func TestNewApp(t *testing.T) {
 		t.Fatalf("unexpected WWW-Authenticate header: %q != %q", e, a)
 	}

-	var errs v2.Errors
+	var errs errcode.Errors
 	dec := json.NewDecoder(req.Body)
 	if err := dec.Decode(&errs); err != nil {
 		t.Fatalf("error decoding error response: %v", err)
 	}

-	if errs.Errors[0].Code != v2.ErrorCodeUnauthorized {
-		t.Fatalf("unexpected error code: %v != %v", errs.Errors[0].Code, v2.ErrorCodeUnauthorized)
+	err2, ok := errs[0].(errcode.ErrorCoder)
+	if !ok {
+		t.Fatalf("not an ErrorCoder: %#v", errs[0])
+	}
+	if err2.ErrorCode() != v2.ErrorCodeUnauthorized {
+		t.Fatalf("unexpected error code: %v != %v", err2.ErrorCode(), v2.ErrorCodeUnauthorized)
 	}
 }

--- a/docs/handlers/blob.go
+++ b/docs/handlers/blob.go
@ -6,6 +6,7 @@ import (
 	"github.com/docker/distribution"
 	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/gorilla/handlers"
 )
@ -17,13 +18,12 @@ func blobDispatcher(ctx *Context, r *http.Request) http.Handler {

 		if err == errDigestNotAvailable {
 			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				w.WriteHeader(http.StatusNotFound)
-				ctx.Errors.Push(v2.ErrorCodeDigestInvalid, err)
+				ctx.Errors = append(ctx.Errors, v2.ErrorCodeDigestInvalid.WithDetail(err))
 			})
 		}

 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			ctx.Errors.Push(v2.ErrorCodeDigestInvalid, err)
+			ctx.Errors = append(ctx.Errors, v2.ErrorCodeDigestInvalid.WithDetail(err))
 		})
 	}

@ -53,17 +53,16 @@ func (bh *blobHandler) GetBlob(w http.ResponseWriter, r *http.Request) {
 	desc, err := blobs.Stat(bh, bh.Digest)
 	if err != nil {
 		if err == distribution.ErrBlobUnknown {
-			w.WriteHeader(http.StatusNotFound)
-			bh.Errors.Push(v2.ErrorCodeBlobUnknown, bh.Digest)
+			bh.Errors = append(bh.Errors, v2.ErrorCodeBlobUnknown.WithDetail(bh.Digest))
 		} else {
-			bh.Errors.Push(v2.ErrorCodeUnknown, err)
+			bh.Errors = append(bh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		}
 		return
 	}

 	if err := blobs.ServeBlob(bh, w, r, desc.Digest); err != nil {
 		context.GetLogger(bh).Debugf("unexpected error getting blob HTTP handler: %v", err)
-		bh.Errors.Push(v2.ErrorCodeUnknown, err)
+		bh.Errors = append(bh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}
 }
--- a/docs/handlers/blobupload.go
+++ b/docs/handlers/blobupload.go
@ -10,6 +10,7 @@ import (
 	"github.com/docker/distribution"
 	ctxu "github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/gorilla/handlers"
 )
@ -36,8 +37,7 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 		if err != nil {
 			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				ctxu.GetLogger(ctx).Infof("error resolving upload: %v", err)
-				w.WriteHeader(http.StatusBadRequest)
-				buh.Errors.Push(v2.ErrorCodeBlobUploadInvalid, err)
+				buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadInvalid.WithDetail(err))
 			})
 		}
 		buh.State = state
@ -45,16 +45,14 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 		if state.Name != ctx.Repository.Name() {
 			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				ctxu.GetLogger(ctx).Infof("mismatched repository name in upload state: %q != %q", state.Name, buh.Repository.Name())
-				w.WriteHeader(http.StatusBadRequest)
-				buh.Errors.Push(v2.ErrorCodeBlobUploadInvalid, err)
+				buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadInvalid.WithDetail(err))
 			})
 		}

 		if state.UUID != buh.UUID {
 			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 				ctxu.GetLogger(ctx).Infof("mismatched uuid in upload state: %q != %q", state.UUID, buh.UUID)
-				w.WriteHeader(http.StatusBadRequest)
-				buh.Errors.Push(v2.ErrorCodeBlobUploadInvalid, err)
+				buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadInvalid.WithDetail(err))
 			})
 		}

@ -64,14 +62,12 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 			ctxu.GetLogger(ctx).Errorf("error resolving upload: %v", err)
 			if err == distribution.ErrBlobUploadUnknown {
 				return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-					w.WriteHeader(http.StatusNotFound)
-					buh.Errors.Push(v2.ErrorCodeBlobUploadUnknown, err)
+					buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadUnknown.WithDetail(err))
 				})
 			}

 			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				w.WriteHeader(http.StatusInternalServerError)
-				buh.Errors.Push(v2.ErrorCodeUnknown, err)
+				buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 			})
 		}
 		buh.Upload = upload
@ -85,16 +81,14 @@ func blobUploadDispatcher(ctx *Context, r *http.Request) http.Handler {
 				defer upload.Close()
 				ctxu.GetLogger(ctx).Infof("error seeking blob upload: %v", err)
 				return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-					w.WriteHeader(http.StatusBadRequest)
-					buh.Errors.Push(v2.ErrorCodeBlobUploadInvalid, err)
+					buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadInvalid.WithDetail(err))
 					upload.Cancel(buh)
 				})
 			} else if nn != buh.State.Offset {
 				defer upload.Close()
 				ctxu.GetLogger(ctx).Infof("seek to wrong offest: %d != %d", nn, buh.State.Offset)
 				return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-					w.WriteHeader(http.StatusBadRequest)
-					buh.Errors.Push(v2.ErrorCodeBlobUploadInvalid, err)
+					buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadInvalid.WithDetail(err))
 					upload.Cancel(buh)
 				})
 			}
@ -125,8 +119,7 @@ func (buh *blobUploadHandler) StartBlobUpload(w http.ResponseWriter, r *http.Req
 	blobs := buh.Repository.Blobs(buh)
 	upload, err := blobs.Create(buh)
 	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError) // Error conditions here?
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

@ -134,8 +127,7 @@ func (buh *blobUploadHandler) StartBlobUpload(w http.ResponseWriter, r *http.Req
 	defer buh.Upload.Close()

 	if err := buh.blobUploadResponse(w, r, true); err != nil {
-		w.WriteHeader(http.StatusInternalServerError) // Error conditions here?
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

@ -146,8 +138,7 @@ func (buh *blobUploadHandler) StartBlobUpload(w http.ResponseWriter, r *http.Req
 // GetUploadStatus returns the status of a given upload, identified by id.
 func (buh *blobUploadHandler) GetUploadStatus(w http.ResponseWriter, r *http.Request) {
 	if buh.Upload == nil {
-		w.WriteHeader(http.StatusNotFound)
-		buh.Errors.Push(v2.ErrorCodeBlobUploadUnknown)
+		buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadUnknown)
 		return
 	}

@ -155,8 +146,7 @@ func (buh *blobUploadHandler) GetUploadStatus(w http.ResponseWriter, r *http.Req
 	// resumable upload is supported. This will enable returning a non-zero
 	// range for clients to begin uploading at an offset.
 	if err := buh.blobUploadResponse(w, r, true); err != nil {
-		w.WriteHeader(http.StatusInternalServerError) // Error conditions here?
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

@ -167,14 +157,13 @@ func (buh *blobUploadHandler) GetUploadStatus(w http.ResponseWriter, r *http.Req
 // PatchBlobData writes data to an upload.
 func (buh *blobUploadHandler) PatchBlobData(w http.ResponseWriter, r *http.Request) {
 	if buh.Upload == nil {
-		w.WriteHeader(http.StatusNotFound)
-		buh.Errors.Push(v2.ErrorCodeBlobUploadUnknown)
+		buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadUnknown)
 		return
 	}

 	ct := r.Header.Get("Content-Type")
 	if ct != "" && ct != "application/octet-stream" {
-		w.WriteHeader(http.StatusBadRequest)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(fmt.Errorf("Bad Content-Type")))
 		// TODO(dmcgowan): encode error
 		return
 	}
@ -184,14 +173,12 @@ func (buh *blobUploadHandler) PatchBlobData(w http.ResponseWriter, r *http.Reque
 	// Copy the data
 	if _, err := io.Copy(buh.Upload, r.Body); err != nil {
 		ctxu.GetLogger(buh).Errorf("unknown error copying into upload: %v", err)
-		w.WriteHeader(http.StatusInternalServerError)
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

 	if err := buh.blobUploadResponse(w, r, false); err != nil {
-		w.WriteHeader(http.StatusInternalServerError) // Error conditions here?
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

@ -205,8 +192,7 @@ func (buh *blobUploadHandler) PatchBlobData(w http.ResponseWriter, r *http.Reque
 // url of the blob.
 func (buh *blobUploadHandler) PutBlobUploadComplete(w http.ResponseWriter, r *http.Request) {
 	if buh.Upload == nil {
-		w.WriteHeader(http.StatusNotFound)
-		buh.Errors.Push(v2.ErrorCodeBlobUploadUnknown)
+		buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadUnknown)
 		return
 	}

@ -214,24 +200,21 @@ func (buh *blobUploadHandler) PutBlobUploadComplete(w http.ResponseWriter, r *ht

 	if dgstStr == "" {
 		// no digest? return error, but allow retry.
-		w.WriteHeader(http.StatusBadRequest)
-		buh.Errors.Push(v2.ErrorCodeDigestInvalid, "digest missing")
+		buh.Errors = append(buh.Errors, v2.ErrorCodeDigestInvalid.WithDetail("digest missing"))
 		return
 	}

 	dgst, err := digest.ParseDigest(dgstStr)
 	if err != nil {
 		// no digest? return error, but allow retry.
-		w.WriteHeader(http.StatusNotFound)
-		buh.Errors.Push(v2.ErrorCodeDigestInvalid, "digest parsing failed")
+		buh.Errors = append(buh.Errors, v2.ErrorCodeDigestInvalid.WithDetail("digest parsing failed"))
 		return
 	}

 	// Read in the data, if any.
 	if _, err := io.Copy(buh.Upload, r.Body); err != nil {
 		ctxu.GetLogger(buh).Errorf("unknown error copying into upload: %v", err)
-		w.WriteHeader(http.StatusInternalServerError)
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

@ -246,17 +229,14 @@ func (buh *blobUploadHandler) PutBlobUploadComplete(w http.ResponseWriter, r *ht
 	if err != nil {
 		switch err := err.(type) {
 		case distribution.ErrBlobInvalidDigest:
-			w.WriteHeader(http.StatusBadRequest)
-			buh.Errors.Push(v2.ErrorCodeDigestInvalid, err)
+			buh.Errors = append(buh.Errors, v2.ErrorCodeDigestInvalid.WithDetail(err))
 		default:
 			switch err {
 			case distribution.ErrBlobInvalidLength, distribution.ErrBlobDigestUnsupported:
-				w.WriteHeader(http.StatusBadRequest)
-				buh.Errors.Push(v2.ErrorCodeBlobUploadInvalid, err)
+				buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadInvalid.WithDetail(err))
 			default:
 				ctxu.GetLogger(buh).Errorf("unknown error completing upload: %#v", err)
-				w.WriteHeader(http.StatusInternalServerError)
-				buh.Errors.Push(v2.ErrorCodeUnknown, err)
+				buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 			}

 		}
@ -273,8 +253,7 @@ func (buh *blobUploadHandler) PutBlobUploadComplete(w http.ResponseWriter, r *ht
 	// Build our canonical blob url
 	blobURL, err := buh.urlBuilder.BuildBlobURL(buh.Repository.Name(), desc.Digest)
 	if err != nil {
-		buh.Errors.Push(v2.ErrorCodeUnknown, err)
-		w.WriteHeader(http.StatusInternalServerError)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}

@ -287,16 +266,14 @@ func (buh *blobUploadHandler) PutBlobUploadComplete(w http.ResponseWriter, r *ht
 // CancelBlobUpload cancels an in-progress upload of a blob.
 func (buh *blobUploadHandler) CancelBlobUpload(w http.ResponseWriter, r *http.Request) {
 	if buh.Upload == nil {
-		w.WriteHeader(http.StatusNotFound)
-		buh.Errors.Push(v2.ErrorCodeBlobUploadUnknown)
+		buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadUnknown)
 		return
 	}

 	w.Header().Set("Docker-Upload-UUID", buh.UUID)
 	if err := buh.Upload.Cancel(buh); err != nil {
 		ctxu.GetLogger(buh).Errorf("error encountered canceling upload: %v", err)
-		w.WriteHeader(http.StatusInternalServerError)
-		buh.Errors.PushErr(err)
+		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 	}

 	w.WriteHeader(http.StatusNoContent)
--- a/docs/handlers/context.go
+++ b/docs/handlers/context.go
@ -8,6 +8,7 @@ import (
 	"github.com/docker/distribution"
 	ctxu "github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"golang.org/x/net/context"
 )
@ -27,7 +28,7 @@ type Context struct {
 	// Errors is a collection of errors encountered during the request to be
 	// returned to the client API. If errors are added to the collection, the
 	// handler *must not* start the response via http.ResponseWriter.
-	Errors v2.Errors
+	Errors errcode.Errors

 	urlBuilder *v2.URLBuilder

--- a/docs/handlers/helpers.go
+++ b/docs/handlers/helpers.go
@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"io"
 	"net/http"
+
+	"github.com/docker/distribution/registry/api/errcode"
 )

 // serveJSON marshals v and sets the content-type header to
@ -11,6 +13,22 @@ import (
 // ResponseWriter.WriteHeader before this function.
 func serveJSON(w http.ResponseWriter, v interface{}) error {
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	sc := http.StatusInternalServerError
+
+	if errs, ok := v.(errcode.Errors); ok && len(errs) > 0 {
+		if err, ok := errs[0].(errcode.ErrorCoder); ok {
+			if sc2 := err.ErrorCode().Descriptor().HTTPStatusCode; sc2 != 0 {
+				sc = sc2
+			}
+		}
+	} else if err, ok := v.(errcode.ErrorCoder); ok {
+		if sc2 := err.ErrorCode().Descriptor().HTTPStatusCode; sc2 != 0 {
+			sc = sc2
+		}
+	}
+
+	w.WriteHeader(sc)
+
 	enc := json.NewEncoder(w)

 	if err := enc.Encode(v); err != nil {
--- a/docs/handlers/images.go
+++ b/docs/handlers/images.go
@ -10,6 +10,7 @@ import (
 	ctxu "github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
 	"github.com/docker/distribution/manifest"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/gorilla/handlers"
 	"golang.org/x/net/context"
@ -63,8 +64,7 @@ func (imh *imageManifestHandler) GetImageManifest(w http.ResponseWriter, r *http
 	}

 	if err != nil {
-		imh.Errors.Push(v2.ErrorCodeManifestUnknown, err)
-		w.WriteHeader(http.StatusNotFound)
+		imh.Errors = append(imh.Errors, v2.ErrorCodeManifestUnknown.WithDetail(err))
 		return
 	}

@ -72,8 +72,7 @@ func (imh *imageManifestHandler) GetImageManifest(w http.ResponseWriter, r *http
 	if imh.Digest == "" {
 		dgst, err := digestManifest(imh, sm)
 		if err != nil {
-			imh.Errors.Push(v2.ErrorCodeDigestInvalid, err)
-			w.WriteHeader(http.StatusBadRequest)
+			imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid.WithDetail(err))
 			return
 		}

@ -94,15 +93,13 @@ func (imh *imageManifestHandler) PutImageManifest(w http.ResponseWriter, r *http

 	var manifest manifest.SignedManifest
 	if err := dec.Decode(&manifest); err != nil {
-		imh.Errors.Push(v2.ErrorCodeManifestInvalid, err)
-		w.WriteHeader(http.StatusBadRequest)
+		imh.Errors = append(imh.Errors, v2.ErrorCodeManifestInvalid.WithDetail(err))
 		return
 	}

 	dgst, err := digestManifest(imh, &manifest)
 	if err != nil {
-		imh.Errors.Push(v2.ErrorCodeDigestInvalid, err)
-		w.WriteHeader(http.StatusBadRequest)
+		imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid.WithDetail(err))
 		return
 	}

@ -110,8 +107,7 @@ func (imh *imageManifestHandler) PutImageManifest(w http.ResponseWriter, r *http
 	if imh.Tag != "" {
 		if manifest.Tag != imh.Tag {
 			ctxu.GetLogger(imh).Errorf("invalid tag on manifest payload: %q != %q", manifest.Tag, imh.Tag)
-			imh.Errors.Push(v2.ErrorCodeTagInvalid)
-			w.WriteHeader(http.StatusBadRequest)
+			imh.Errors = append(imh.Errors, v2.ErrorCodeTagInvalid)
 			return
 		}

@ -119,13 +115,11 @@ func (imh *imageManifestHandler) PutImageManifest(w http.ResponseWriter, r *http
 	} else if imh.Digest != "" {
 		if dgst != imh.Digest {
 			ctxu.GetLogger(imh).Errorf("payload digest does match: %q != %q", dgst, imh.Digest)
-			imh.Errors.Push(v2.ErrorCodeDigestInvalid)
-			w.WriteHeader(http.StatusBadRequest)
+			imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid)
 			return
 		}
 	} else {
-		imh.Errors.Push(v2.ErrorCodeTagInvalid, "no tag or digest specified")
-		w.WriteHeader(http.StatusBadRequest)
+		imh.Errors = append(imh.Errors, v2.ErrorCodeTagInvalid.WithDetail("no tag or digest specified"))
 		return
 	}

@ -137,22 +131,21 @@ func (imh *imageManifestHandler) PutImageManifest(w http.ResponseWriter, r *http
 			for _, verificationError := range err {
 				switch verificationError := verificationError.(type) {
 				case distribution.ErrManifestBlobUnknown:
-					imh.Errors.Push(v2.ErrorCodeBlobUnknown, verificationError.Digest)
+					imh.Errors = append(imh.Errors, v2.ErrorCodeBlobUnknown.WithDetail(verificationError.Digest))
 				case distribution.ErrManifestUnverified:
-					imh.Errors.Push(v2.ErrorCodeManifestUnverified)
+					imh.Errors = append(imh.Errors, v2.ErrorCodeManifestUnverified)
 				default:
 					if verificationError == digest.ErrDigestInvalidFormat {
-						imh.Errors.Push(v2.ErrorCodeDigestInvalid)
+						imh.Errors = append(imh.Errors, v2.ErrorCodeDigestInvalid)
 					} else {
-						imh.Errors.PushErr(verificationError)
+						imh.Errors = append(imh.Errors, errcode.ErrorCodeUnknown, verificationError)
 					}
 				}
 			}
 		default:
-			imh.Errors.PushErr(err)
+			imh.Errors = append(imh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		}

-		w.WriteHeader(http.StatusBadRequest)
 		return
 	}

@ -179,8 +172,7 @@ func (imh *imageManifestHandler) DeleteImageManifest(w http.ResponseWriter, r *h
 	// tag index entries a serious problem in eventually consistent storage.
 	// Once we work out schema version 2, the full deletion system will be
 	// worked out and we can add support back.
-	imh.Errors.Push(v2.ErrorCodeUnsupported)
-	w.WriteHeader(http.StatusBadRequest)
+	imh.Errors = append(imh.Errors, v2.ErrorCodeUnsupported)
 }

 // digestManifest takes a digest of the given manifest. This belongs somewhere
--- a/docs/handlers/tags.go
+++ b/docs/handlers/tags.go
@ -5,6 +5,7 @@ import (
 	"net/http"

 	"github.com/docker/distribution"
+	"github.com/docker/distribution/registry/api/errcode"
 	"github.com/docker/distribution/registry/api/v2"
 	"github.com/gorilla/handlers"
 )
@ -39,10 +40,9 @@ func (th *tagsHandler) GetTags(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		switch err := err.(type) {
 		case distribution.ErrRepositoryUnknown:
-			w.WriteHeader(404)
-			th.Errors.Push(v2.ErrorCodeNameUnknown, map[string]string{"name": th.Repository.Name()})
+			th.Errors = append(th.Errors, v2.ErrorCodeNameUnknown.WithDetail(map[string]string{"name": th.Repository.Name()}))
 		default:
-			th.Errors.PushErr(err)
+			th.Errors = append(th.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		}
 		return
 	}
@ -54,7 +54,7 @@ func (th *tagsHandler) GetTags(w http.ResponseWriter, r *http.Request) {
 		Name: th.Repository.Name(),
 		Tags: tags,
 	}); err != nil {
-		th.Errors.PushErr(err)
+		th.Errors = append(th.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 		return
 	}
 }