Merge pull request #705 from stevvooe/export-servejson-errors

Export ServeJSON for serving error codes

docs/api/errcode/errors.go

@@ -16,6 +16,8 @@ type ErrorCoder interface {
 // and the integer format may change and should *never* be exported.
 type ErrorCode int
 
+var _ error = ErrorCode(0)
+
 // ErrorCode just returns itself
 func (ec ErrorCode) ErrorCode() ErrorCode {
 	return ec
@@ -93,6 +95,8 @@ type Error struct {
 	// variable substitution right before showing the message to the user
 }
 
+var _ error = Error{}
+
 // ErrorCode returns the ID/Value of this Error
 func (e Error) ErrorCode() ErrorCode {
 	return e.Code
@@ -163,6 +167,8 @@ func ParseErrorCode(value string) ErrorCode {
 // for use within the application.
 type Errors []error
 
+var _ error = Errors{}
+
 func (errs Errors) Error() string {
 	switch len(errs) {
 	case 0:

docs/api/errcode/handler.go

@@ -0,0 +1,44 @@
+package errcode
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+// ServeJSON attempts to serve the errcode in a JSON envelope. It marshals err
+// and sets the content-type header to 'application/json'. It will handle
+// ErrorCoder and Errors, and if necessary will create an envelope.
+func ServeJSON(w http.ResponseWriter, err error) error {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	var sc int
+
+	switch errs := err.(type) {
+	case Errors:
+		if len(errs) < 1 {
+			break
+		}
+
+		if err, ok := errs[0].(ErrorCoder); ok {
+			sc = err.ErrorCode().Descriptor().HTTPStatusCode
+		}
+	case ErrorCoder:
+		sc = errs.ErrorCode().Descriptor().HTTPStatusCode
+		err = Errors{err} // create an envelope.
+	default:
+		// We just have an unhandled error type, so just place in an envelope
+		// and move along.
+		err = Errors{err}
+	}
+
+	if sc == 0 {
+		sc = http.StatusInternalServerError
+	}
+
+	w.WriteHeader(sc)
+
+	if err := json.NewEncoder(w).Encode(err); err != nil {
+		return err
+	}
+
+	return nil
+}

docs/handlers/app.go

@@ -379,7 +379,9 @@ func (app *App) dispatcher(dispatch dispatchFunc) http.Handler {
 					context.Errors = append(context.Errors, v2.ErrorCodeNameInvalid.WithDetail(err))
 				}
 
-				serveJSON(w, context.Errors)
+				if err := errcode.ServeJSON(w, context.Errors); err != nil {
+					ctxu.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)
+				}
 				return
 			}
 
@@ -393,7 +395,9 @@ func (app *App) dispatcher(dispatch dispatchFunc) http.Handler {
 				ctxu.GetLogger(context).Errorf("error initializing repository middleware: %v", err)
 				context.Errors = append(context.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
 
-				serveJSON(w, context.Errors)
+				if err := errcode.ServeJSON(w, context.Errors); err != nil {
+					ctxu.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)
+				}
 				return
 			}
 		}
@@ -405,7 +409,9 @@ func (app *App) dispatcher(dispatch dispatchFunc) http.Handler {
 		if context.Errors.Len() > 0 {
 			app.logError(context, context.Errors)
 
-			serveJSON(w, context.Errors)
+			if err := errcode.ServeJSON(w, context.Errors); err != nil {
+				ctxu.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)
+			}
 		}
 	})
 }
@@ -482,11 +488,9 @@ 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.
-
-			var errs errcode.Errors
-			errs = append(errs, v2.ErrorCodeUnauthorized)
-
-			serveJSON(w, errs)
+			if err := errcode.ServeJSON(w, v2.ErrorCodeUnauthorized); err != nil {
+				ctxu.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)
+			}
 			return fmt.Errorf("forbidden: no repository name")
 		}
 	}
@@ -498,9 +502,9 @@ func (app *App) authorized(w http.ResponseWriter, r *http.Request, context *Cont
 			// Add the appropriate WWW-Auth header
 			err.ServeHTTP(w, r)
 
-			var errs errcode.Errors
-			errs = append(errs, v2.ErrorCodeUnauthorized.WithDetail(accessRecords))
-			serveJSON(w, errs)
+			if err := errcode.ServeJSON(w, v2.ErrorCodeUnauthorized.WithDetail(accessRecords)); err != nil {
+				ctxu.GetLogger(context).Errorf("error serving error json: %v (from %v)", err, context.Errors)
+			}
 		default:
 			// This condition is a potential security problem either in
 			// the configuration or whatever is backing the access

docs/handlers/helpers.go

@@ -1,43 +1,10 @@
 package handlers
 
 import (
-	"encoding/json"
 	"io"
 	"net/http"
-
-	"github.com/docker/distribution/registry/api/errcode"
 )
 
-// serveJSON marshals v and sets the content-type header to
-// 'application/json'. If a different status code is required, call
-// 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 {
-		return err
-	}
-
-	return nil
-}
-
 // closeResources closes all the provided resources after running the target
 // handler.
 func closeResources(handler http.Handler, closers ...io.Closer) http.Handler {