Refactor printers to separate typed printers from generic code

pkg/printers/interface.go

@@ -17,6 +17,7 @@ limitations under the License.
 package printers
 
 import (
+	"fmt"
 	"io"
 
 	"k8s.io/apimachinery/pkg/runtime"
@@ -60,3 +61,36 @@ type PrintOptions struct {
 	Kind               string
 	ColumnLabels       []string
 }
+
+// Describer generates output for the named resource or an error
+// if the output could not be generated. Implementers typically
+// abstract the retrieval of the named object from a remote server.
+type Describer interface {
+	Describe(namespace, name string, describerSettings DescriberSettings) (output string, err error)
+}
+
+// DescriberSettings holds display configuration for each object
+// describer to control what is printed.
+type DescriberSettings struct {
+	ShowEvents bool
+}
+
+// ObjectDescriber is an interface for displaying arbitrary objects with extra
+// information. Use when an object is in hand (on disk, or already retrieved).
+// Implementers may ignore the additional information passed on extra, or use it
+// by default. ObjectDescribers may return ErrNoDescriber if no suitable describer
+// is found.
+type ObjectDescriber interface {
+	DescribeObject(object interface{}, extra ...interface{}) (output string, err error)
+}
+
+// ErrNoDescriber is a structured error indicating the provided object or objects
+// cannot be described.
+type ErrNoDescriber struct {
+	Types []string
+}
+
+// Error implements the error interface.
+func (e ErrNoDescriber) Error() string {
+	return fmt.Sprintf("no describer has been defined for %v", e.Types)
+}