Add a strongly typed error for unrecognized kind/type/version

pkg/conversion/decode.go

@@ -115,7 +115,7 @@ func (s *Scheme) DecodeInto(data []byte, obj interface{}) error {
 	} else {
 		external, err := s.NewObject(dataVersion, dataKind)
 		if err != nil {
-			return fmt.Errorf("unable to create new object of type ('%s', '%s')", dataVersion, dataKind)
+			return err
 		}
 		// yaml is a superset of json, so we use it to decode here. That way,
 		// we understand both.

pkg/conversion/error.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package conversion
+
+import (
+	"fmt"
+	"reflect"
+)
+
+type notRegisteredErr struct {
+	kind    string
+	version string
+	t       reflect.Type
+}
+
+func (k *notRegisteredErr) Error() string {
+	if k.t != nil {
+		return fmt.Sprintf("no kind is registered for the type %v", k.t)
+	}
+	if len(k.kind) == 0 {
+		return fmt.Sprintf("no version %q has been registered", k.version)
+	}
+	if len(k.version) == 0 {
+		return fmt.Sprintf("no kind %q is registered for the default version", k.kind)
+	}
+	return fmt.Sprintf("no kind %q is registered for version %q", k.kind, k.version)
+}
+
+// IsNotRegisteredError returns true if the error indicates the provided
+// object or input data is not registered.
+func IsNotRegisteredError(err error) bool {
+	if err == nil {
+		return false
+	}
+	_, ok := err.(*notRegisteredErr)
+	return ok
+}

pkg/conversion/scheme.go

@@ -143,14 +143,14 @@ func (s *Scheme) KnownTypes(version string) map[string]reflect.Type {
 
 // NewObject returns a new object of the given version and name,
 // or an error if it hasn't been registered.
-func (s *Scheme) NewObject(versionName, typeName string) (interface{}, error) {
+func (s *Scheme) NewObject(versionName, kind string) (interface{}, error) {
 	if types, ok := s.versionMap[versionName]; ok {
-		if t, ok := types[typeName]; ok {
+		if t, ok := types[kind]; ok {
 			return reflect.New(t).Interface(), nil
 		}
-		return nil, fmt.Errorf("no type '%v' for version '%v'", typeName, versionName)
+		return nil, &notRegisteredErr{kind: kind, version: versionName}
 	}
-	return nil, fmt.Errorf("no version '%v'", versionName)
+	return nil, &notRegisteredErr{kind: kind, version: versionName}
 }
 
 // AddConversionFuncs adds functions to the list of conversion functions. The given
@@ -284,7 +284,7 @@ func (s *Scheme) ObjectVersionAndKind(obj interface{}) (apiVersion, kind string,
 	version, vOK := s.typeToVersion[t]
 	kinds, kOK := s.typeToKind[t]
 	if !vOK || !kOK {
-		return "", "", fmt.Errorf("unregistered type: %v", t)
+		return "", "", &notRegisteredErr{t: t}
 	}
 	apiVersion = version
 	kind = kinds[0]

pkg/runtime/error.go

@@ -0,0 +1,27 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package runtime
+
+import (
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/conversion"
+)
+
+// IsNotRegisteredError returns true if the error indicates the provided
+// object or input data is not registered.
+func IsNotRegisteredError(err error) bool {
+	return conversion.IsNotRegisteredError(err)
+}