attempt to use discovery RESTMapper and fallback if we can't

pkg/kubectl/cmd/util/factory.go

@@ -32,7 +32,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/blang/semver"
 	"github.com/emicklei/go-restful/swagger"
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
@@ -334,26 +333,23 @@ func (f *factory) Object() (meta.RESTMapper, runtime.ObjectTyper) {
 
 	mapper := registered.RESTMapper()
 	discoveryClient, err := discovery.NewDiscoveryClientForConfig(cfg)
-	// if we can find the server version and it's current enough to have discovery information, use it.  Otherwise,
-	// fallback to our hardcoded list
 	if err == nil {
-		if serverVersion, err := discoveryClient.ServerVersion(); err == nil && useDiscoveryRESTMapper(serverVersion.GitVersion) {
-			// register third party resources with the api machinery groups.  This probably should be done, but
-			// its consistent with old code, so we'll start with it.
-			if err := registerThirdPartyResources(discoveryClient); err != nil {
-				fmt.Fprintf(os.Stderr, "Unable to register third party resources: %v\n", err)
-			}
-			// ThirdPartyResourceData is special.  It's not discoverable, but needed for thirdparty resource listing
-			// TODO eliminate this once we're truly generic.
-			thirdPartyResourceDataMapper := meta.NewDefaultRESTMapper([]unversioned.GroupVersion{extensionsv1beta1.SchemeGroupVersion}, registered.InterfacesFor)
-			thirdPartyResourceDataMapper.Add(extensionsv1beta1.SchemeGroupVersion.WithKind("ThirdPartyResourceData"), meta.RESTScopeNamespace)
-
-			mapper = meta.FirstHitRESTMapper{
-				MultiRESTMapper: meta.MultiRESTMapper{
-					discovery.NewDeferredDiscoveryRESTMapper(discoveryClient, registered.InterfacesFor),
-					thirdPartyResourceDataMapper,
-				},
-			}
+		// register third party resources with the api machinery groups.  This probably should be done, but
+		// its consistent with old code, so we'll start with it.
+		if err := registerThirdPartyResources(discoveryClient); err != nil {
+			fmt.Fprintf(os.Stderr, "Unable to register third party resources: %v\n", err)
+		}
+		// ThirdPartyResourceData is special.  It's not discoverable, but needed for thirdparty resource listing
+		// TODO eliminate this once we're truly generic.
+		thirdPartyResourceDataMapper := meta.NewDefaultRESTMapper([]unversioned.GroupVersion{extensionsv1beta1.SchemeGroupVersion}, registered.InterfacesFor)
+		thirdPartyResourceDataMapper.Add(extensionsv1beta1.SchemeGroupVersion.WithKind("ThirdPartyResourceData"), meta.RESTScopeNamespace)
+
+		mapper = meta.FirstHitRESTMapper{
+			MultiRESTMapper: meta.MultiRESTMapper{
+				discovery.NewDeferredDiscoveryRESTMapper(discoveryClient, registered.InterfacesFor),
+				thirdPartyResourceDataMapper, // needed for TPR printing
+				registered.RESTMapper(),      // hardcoded fall back
+			},
 		}
 	}
 
@@ -1332,20 +1328,6 @@ func (f *factory) NewBuilder() *resource.Builder {
 	return resource.NewBuilder(mapper, typer, resource.ClientMapperFunc(f.ClientForMapping), f.Decoder(true))
 }
 
-// useDiscoveryRESTMapper checks the server version to see if its recent enough to have
-// enough discovery information available to reliably build a RESTMapper.  If not, use the
-// hardcoded mapper in this client (legacy behavior)
-func useDiscoveryRESTMapper(serverVersion string) bool {
-	if len(serverVersion) == 0 {
-		return false
-	}
-	serverSemVer, err := semver.Parse(serverVersion[1:])
-	if err != nil {
-		return false
-	}
-	return serverSemVer.GE(semver.MustParse("1.3.0"))
-}
-
 // registerThirdPartyResources inspects the discovery endpoint to find thirdpartyresources in the discovery doc
 // and then registers them with the apimachinery code.  I think this is done so that scheme/codec stuff works,
 // but I really don't know.  Feels like this code should go away once kubectl is completely generic for generic