kubectl dry-run: Check for server didn't work on create

We changed the code to verify that the type supports dry-run, but we've
only done it for patch, not for create, which means that people can
create objects they don't want to create. We can actually simplify the
code by moving the check much earlier in the method, which fixes all
possible bug like this.

pkg/kubectl/cmd/diff/diff.go

@@ -26,7 +26,6 @@ import (
 	"github.com/ghodss/yaml"
 	"github.com/jonboulle/clockwork"
 	"github.com/spf13/cobra"
-
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -226,11 +225,10 @@ type Object interface {
 // InfoObject is an implementation of the Object interface. It gets all
 // the information from the Info object.
 type InfoObject struct {
-	LocalObj       runtime.Object
-	Info           *resource.Info
-	Encoder        runtime.Encoder
-	OpenAPI        openapi.Resources
-	DryRunVerifier *apply.DryRunVerifier
+	LocalObj runtime.Object
+	Info     *resource.Info
+	Encoder  runtime.Encoder
+	OpenAPI  openapi.Resources
 }
 
 var _ Object = &InfoObject{}
@@ -262,13 +260,12 @@ func (obj InfoObject) Merged() (runtime.Object, error) {
 	// This is using the patcher from apply, to keep the same behavior.
 	// We plan on replacing this with server-side apply when it becomes available.
 	patcher := &apply.Patcher{
-		DryRunVerifier: obj.DryRunVerifier,
-		Mapping:        obj.Info.Mapping,
-		Helper:         resource.NewHelper(obj.Info.Client, obj.Info.Mapping),
-		Overwrite:      true,
-		BackOff:        clockwork.NewRealClock(),
-		ServerDryRun:   true,
-		OpenapiSchema:  obj.OpenAPI,
+		Mapping:       obj.Info.Mapping,
+		Helper:        resource.NewHelper(obj.Info.Client, obj.Info.Mapping),
+		Overwrite:     true,
+		BackOff:       clockwork.NewRealClock(),
+		ServerDryRun:  true,
+		OpenapiSchema: obj.OpenAPI,
 	}
 
 	_, result, err := patcher.Patch(obj.Info.Object, modified, obj.Info.Source, obj.Info.Namespace, obj.Info.Name, nil)
@@ -375,6 +372,10 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions) error {
 			return err
 		}
 
+		if err := dryRunVerifier.HasSupport(info.Mapping.GroupVersionKind); err != nil {
+			return err
+		}
+
 		local := info.Object.DeepCopyObject()
 		if err := info.Get(); err != nil {
 			if !errors.IsNotFound(err) {
@@ -384,11 +385,10 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions) error {
 		}
 
 		obj := InfoObject{
-			LocalObj:       local,
-			Info:           info,
-			Encoder:        scheme.DefaultJSONEncoder(),
-			OpenAPI:        schema,
-			DryRunVerifier: dryRunVerifier,
+			LocalObj: local,
+			Info:     info,
+			Encoder:  scheme.DefaultJSONEncoder(),
+			OpenAPI:  schema,
 		}
 
 		return differ.Diff(obj, printer)