List output with differing types should be more resilient

kubectl get can output a series of objects as a List in versioned
form, but not all API objects are available in the same schema.
Make the act of converting a []runtime.Object to api.List more
robust and add a test to verify its behavior in Get.

Makes it easier for client code to output unified objects.

pkg/kubectl/cmd/get_test.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"bytes"
+	encjson "encoding/json"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -138,6 +139,84 @@ func TestGetUnknownSchemaObject(t *testing.T) {
 	}
 }
 
+// Verifies that schemas that are not in the master tree of Kubernetes can be retrieved via Get.
+// Because api.List is part of the Kube API, resource.Builder has to perform a conversion on
+// api.Scheme, which may not have access to all objects, and not all objects are at the same
+// internal versioning scheme. This test verifies that two isolated schemes (Test, and api.Scheme)
+// can be conjoined into a single output object.
+func TestGetUnknownSchemaObjectListGeneric(t *testing.T) {
+	testCases := map[string]struct {
+		output string
+		list   string
+		obj1   string
+		obj2   string
+	}{
+		"handles specific version": {
+			output: "v1beta3",
+			list:   "v1beta3",
+			obj1:   "unlikelyversion",
+			obj2:   "v1beta3",
+		},
+		"handles second specific version": {
+			output: "unlikelyversion",
+			list:   "v1beta3",
+			obj1:   "unlikelyversion", // doesn't have v1beta3
+			obj2:   "v1beta1",         // version of the API response
+		},
+		"handles common version": {
+			output: "v1beta1",
+			list:   "v1beta1",
+			obj1:   "unlikelyversion", // because test scheme defaults to unlikelyversion
+			obj2:   "v1beta1",
+		},
+	}
+	for k, test := range testCases {
+		apiCodec := runtime.CodecFor(api.Scheme, "v1beta1")
+		regularClient := &client.FakeRESTClient{
+			Codec: apiCodec,
+			Client: client.HTTPClientFunc(func(req *http.Request) (*http.Response, error) {
+				return &http.Response{StatusCode: 200, Body: objBody(apiCodec, &api.ReplicationController{ObjectMeta: api.ObjectMeta{Name: "foo"}})}, nil
+			}),
+		}
+
+		f, tf, codec := NewMixedFactory(regularClient)
+		tf.Printer = &testPrinter{}
+		tf.Client = &client.FakeRESTClient{
+			Codec: codec,
+			Client: client.HTTPClientFunc(func(req *http.Request) (*http.Response, error) {
+				return &http.Response{StatusCode: 200, Body: objBody(codec, &internalType{Name: "foo"})}, nil
+			}),
+		}
+		tf.Namespace = "test"
+		tf.ClientConfig = &client.Config{Version: latest.Version}
+		buf := bytes.NewBuffer([]byte{})
+		cmd := NewCmdGet(f, buf)
+		cmd.SetOutput(buf)
+		cmd.Flags().Set("output", "json")
+		cmd.Flags().Set("output-version", test.output)
+		err := RunGet(f, buf, cmd, []string{"type/foo", "replicationcontrollers/foo"})
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", k, err)
+			continue
+		}
+		out := make(map[string]interface{})
+		if err := encjson.Unmarshal(buf.Bytes(), &out); err != nil {
+			t.Errorf("%s: unexpected error: %v\n%s", k, err, buf.String())
+			continue
+		}
+		if out["apiVersion"] != test.list {
+			t.Errorf("%s: unexpected list: %#v", k, out)
+		}
+		arr := out["items"].([]interface{})
+		if arr[0].(map[string]interface{})["apiVersion"] != test.obj1 {
+			t.Errorf("%s: unexpected list: %#v", k, out)
+		}
+		if arr[1].(map[string]interface{})["apiVersion"] != test.obj2 {
+			t.Errorf("%s: unexpected list: %#v", k, out)
+		}
+	}
+}
+
 // Verifies that schemas that are not in the master tree of Kubernetes can be retrieved via Get.
 func TestGetSchemaObject(t *testing.T) {
 	f, tf, _ := NewTestFactory()