dry-run: Verify if the object supports dry-run

For each object, first we verify if they have a dryRun parameter in the
openapi for the patch verb. If we can't find the object, we assume that
CRD will behave like "namespace". So we check if namespace supports
dryRun. If it does, then we verify that the resource is a CRD.

pkg/kubectl/cmd/diff/diff.go

@@ -226,10 +226,11 @@ 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
+	LocalObj       runtime.Object
+	Info           *resource.Info
+	Encoder        runtime.Encoder
+	OpenAPI        openapi.Resources
+	DryRunVerifier *apply.DryRunVerifier
 }
 
 var _ Object = &InfoObject{}
@@ -261,12 +262,13 @@ 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{
-		Mapping:       obj.Info.Mapping,
-		Helper:        resource.NewHelper(obj.Info.Client, obj.Info.Mapping),
-		Overwrite:     true,
-		BackOff:       clockwork.NewRealClock(),
-		ServerDryRun:  true,
-		OpenapiSchema: obj.OpenAPI,
+		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,
 	}
 
 	_, result, err := patcher.Patch(obj.Info.Object, modified, obj.Info.Source, obj.Info.Namespace, obj.Info.Name, nil)
@@ -330,6 +332,21 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions) error {
 		return err
 	}
 
+	discovery, err := f.ToDiscoveryClient()
+	if err != nil {
+		return err
+	}
+
+	dynamic, err := f.DynamicClient()
+	if err != nil {
+		return err
+	}
+
+	dryRunVerifier := &apply.DryRunVerifier{
+		Finder:        cmdutil.NewCRDFinder(cmdutil.CRDFromDynamic(dynamic)),
+		OpenAPIGetter: discovery,
+	}
+
 	differ, err := NewDiffer("LIVE", "MERGED")
 	if err != nil {
 		return err
@@ -367,10 +384,11 @@ func RunDiff(f cmdutil.Factory, diff *DiffProgram, options *DiffOptions) error {
 		}
 
 		obj := InfoObject{
-			LocalObj: local,
-			Info:     info,
-			Encoder:  scheme.DefaultJSONEncoder(),
-			OpenAPI:  schema,
+			LocalObj:       local,
+			Info:           info,
+			Encoder:        scheme.DefaultJSONEncoder(),
+			OpenAPI:        schema,
+			DryRunVerifier: dryRunVerifier,
 		}
 
 		return differ.Diff(obj, printer)