fix(kubectl): explain crds with the same resource name with builtin objects

staging/src/k8s.io/kubectl/pkg/cmd/explain/explain.go

@@ -123,19 +123,14 @@ func (o *ExplainOptions) Run(args []string) error {
 	// TODO: After we figured out the new syntax to separate group and resource, allow
 	// the users to use it in explain (kubectl explain <group><syntax><resource>).
 	// Refer to issue #16039 for why we do this. Refer to PR #15808 that used "/" syntax.
-	inModel, fieldsPath, err := explain.SplitAndParseResourceRequest(args[0], o.Mapper)
+	fullySpecifiedGVR, fieldsPath, err := explain.SplitAndParseResourceRequest(args[0], o.Mapper)
 	if err != nil {
 		return err
 	}
 
-	// TODO: We should deduce the group for a resource by discovering the supported resources at server.
+	gvk, _ := o.Mapper.KindFor(fullySpecifiedGVR)
-	fullySpecifiedGVR, groupResource := schema.ParseResourceArg(inModel)
-	gvk := schema.GroupVersionKind{}
-	if fullySpecifiedGVR != nil {
-		gvk, _ = o.Mapper.KindFor(*fullySpecifiedGVR)
-	}
 	if gvk.Empty() {
-		gvk, err = o.Mapper.KindFor(groupResource.WithVersion(""))
+		gvk, err = o.Mapper.KindFor(fullySpecifiedGVR.GroupResource().WithVersion(""))
 		if err != nil {
 			return err
 		}
@@ -151,7 +146,7 @@ func (o *ExplainOptions) Run(args []string) error {
 
 	schema := o.Schema.LookupResource(gvk)
 	if schema == nil {
-		return fmt.Errorf("Couldn't find resource for %q", gvk)
+		return fmt.Errorf("couldn't find resource for %q", gvk)
 	}
 
 	return explain.PrintModelDescription(fieldsPath, o.Out, schema, gvk, recursive)

staging/src/k8s.io/kubectl/pkg/explain/explain.go

@@ -20,9 +20,10 @@ import (
 	"io"
 	"strings"
 
+	"k8s.io/kube-openapi/pkg/util/proto"
+
 	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apimachinery/pkg/runtime/schema"
-	"k8s.io/kube-openapi/pkg/util/proto"
 )
 
 type fieldsPrinter interface {
@@ -43,10 +44,13 @@ func splitDotNotation(model string) (string, []string) {
 }
 
 // SplitAndParseResourceRequest separates the users input into a model and fields
-func SplitAndParseResourceRequest(inResource string, mapper meta.RESTMapper) (string, []string, error) {
+func SplitAndParseResourceRequest(inResource string, mapper meta.RESTMapper) (schema.GroupVersionResource, []string, error) {
 	inResource, fieldsPath := splitDotNotation(inResource)
-	inResource, _ = mapper.ResourceSingularizer(inResource)
+	gvr, err := mapper.ResourceFor(schema.GroupVersionResource{Resource: inResource})
-	return inResource, fieldsPath, nil
+	if err != nil {
+		return schema.GroupVersionResource{}, nil, err
+	}
+	return gvr, fieldsPath, nil
 }
 
 // PrintModelDescription prints the description of a specific model or dot path.

staging/src/k8s.io/kubectl/pkg/explain/explain_test.go

@@ -21,37 +21,38 @@ import (
 	"testing"
 
 	"k8s.io/apimachinery/pkg/api/meta/testrestmapper"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/kubectl/pkg/scheme"
 )
 
 func TestSplitAndParseResourceRequest(t *testing.T) {
 	tests := []struct {
 		name       string
-		inresource string
+		inResource string
 
-		expectedInResource string
+		expectedGVR        schema.GroupVersionResource
 		expectedFieldsPath []string
 		expectedErr        bool
 	}{
 		{
 			name:       "no trailing period",
-			inresource: "field1.field2.field3",
+			inResource: "pods.field2.field3",
 
-			expectedInResource: "field1",
+			expectedGVR:        schema.GroupVersionResource{Resource: "pods", Version: "v1"},
 			expectedFieldsPath: []string{"field2", "field3"},
 		},
 		{
 			name:       "trailing period with correct fieldsPath",
-			inresource: "field1.field2.field3.",
+			inResource: "service.field2.field3.",
 
-			expectedInResource: "field1",
+			expectedGVR:        schema.GroupVersionResource{Resource: "services", Version: "v1"},
 			expectedFieldsPath: []string{"field2", "field3"},
 		},
 		{
 			name:       "trailing period with incorrect fieldsPath",
-			inresource: "field1.field2.field3.",
+			inResource: "node.field2.field3.",
 
-			expectedInResource: "field1",
+			expectedGVR:        schema.GroupVersionResource{Resource: "nodes", Version: "v1"},
 			expectedFieldsPath: []string{"field2", "field3", ""},
 			expectedErr:        true,
 		},
@@ -60,13 +61,13 @@ func TestSplitAndParseResourceRequest(t *testing.T) {
 	mapper := testrestmapper.TestOnlyStaticRESTMapper(scheme.Scheme, scheme.Scheme.PrioritizedVersionsAllGroups()...)
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			gotInResource, gotFieldsPath, err := SplitAndParseResourceRequest(tt.inresource, mapper)
+			gotGVR, gotFieldsPath, err := SplitAndParseResourceRequest(tt.inResource, mapper)
 			if err != nil {
 				t.Errorf("unexpected error: %v", err)
 			}
 
-			if !reflect.DeepEqual(tt.expectedInResource, gotInResource) && !tt.expectedErr {
+			if !reflect.DeepEqual(tt.expectedGVR, gotGVR) && !tt.expectedErr {
-				t.Errorf("%s: expected inresource: %s, got: %s", tt.name, tt.expectedInResource, gotInResource)
+				t.Errorf("%s: expected inResource: %s, got: %s", tt.name, tt.expectedGVR, gotGVR)
 			}
 
 			if !reflect.DeepEqual(tt.expectedFieldsPath, gotFieldsPath) && !tt.expectedErr {

test/e2e/apimachinery/crd_publish_openapi.go

@@ -68,6 +68,12 @@ var _ = SIGDescribe("CustomResourcePublishOpenAPI [Privileged:ClusterAdmin]", fu
 			framework.Failf("%v", err)
 		}
 
+		customServiceShortName := "ksvc"
+		crdSvc, err := setupCRDWithShortName(f, schemaCustomService, "service", customServiceShortName, "v1alpha1")
+		if err != nil {
+			framework.Failf("%v", err)
+		}
+
 		meta := fmt.Sprintf(metaPattern, crd.Crd.Spec.Names.Kind, crd.Crd.Spec.Group, crd.Crd.Spec.Versions[0].Name, "test-foo")
 		ns := fmt.Sprintf("--namespace=%v", f.Namespace.Name)
 
@@ -120,6 +126,11 @@ var _ = SIGDescribe("CustomResourcePublishOpenAPI [Privileged:ClusterAdmin]", fu
 			framework.Failf("%v", err)
 		}
 
+		ginkgo.By("kubectl explain works for CR with the same resource name as built-in object")
+		if err := verifyKubectlExplain(f.Namespace.Name, customServiceShortName+".spec", `(?s)DESCRIPTION:.*Specification of CustomService.*FIELDS:.*dummy.*<string>.*Dummy property`); err != nil {
+			framework.Failf("%v", err)
+		}
+
 		ginkgo.By("kubectl explain works to return error when explain is called on property that doesn't exist")
 		if _, err := framework.RunKubectl(f.Namespace.Name, "explain", crd.Crd.Spec.Names.Plural+".spec.bars2"); err == nil || !strings.Contains(err.Error(), `field "bars2" does not exist`) {
 			framework.Failf("unexpected no error when explaining property that doesn't exist: %v", err)
@@ -128,6 +139,9 @@ var _ = SIGDescribe("CustomResourcePublishOpenAPI [Privileged:ClusterAdmin]", fu
 		if err := cleanupCRD(f, crd); err != nil {
 			framework.Failf("%v", err)
 		}
+		if err := cleanupCRD(f, crdSvc); err != nil {
+			framework.Failf("%v", err)
+		}
 	})
 
 	/*
@@ -476,7 +490,24 @@ func setupCRD(f *framework.Framework, schema []byte, groupSuffix string, version
 	return setupCRDAndVerifySchema(f, schema, expect, groupSuffix, versions...)
 }
 
+func setupCRDWithShortName(f *framework.Framework, schema []byte, groupSuffix, shortName string, versions ...string) (*crd.TestCrd, error) {
+	expect := schema
+	if schema == nil {
+		// to be backwards compatible, we expect CRD controller to treat
+		// CRD with nil schema specially and publish an empty schema
+		expect = []byte(`type: object`)
+	}
+	setShortName := func(crd *apiextensionsv1.CustomResourceDefinition) {
+		crd.Spec.Names.ShortNames = []string{shortName}
+	}
+	return setupCRDAndVerifySchemaWithOptions(f, schema, expect, groupSuffix, versions, setShortName)
+}
+
 func setupCRDAndVerifySchema(f *framework.Framework, schema, expect []byte, groupSuffix string, versions ...string) (*crd.TestCrd, error) {
+	return setupCRDAndVerifySchemaWithOptions(f, schema, expect, groupSuffix, versions)
+}
+
+func setupCRDAndVerifySchemaWithOptions(f *framework.Framework, schema, expect []byte, groupSuffix string, versions []string, options ...crd.Option) (*crd.TestCrd, error) {
 	group := fmt.Sprintf("%s-test-%s.example.com", f.BaseName, groupSuffix)
 	if len(versions) == 0 {
 		return nil, fmt.Errorf("require at least one version for CRD")
@@ -489,7 +520,7 @@ func setupCRDAndVerifySchema(f *framework.Framework, schema, expect []byte, grou
 		}
 	}
 
-	crd, err := crd.CreateMultiVersionTestCRD(f, group, func(crd *apiextensionsv1.CustomResourceDefinition) {
+	options = append(options, func(crd *apiextensionsv1.CustomResourceDefinition) {
 		var apiVersions []apiextensionsv1.CustomResourceDefinitionVersion
 		for i, version := range versions {
 			version := apiextensionsv1.CustomResourceDefinitionVersion{
@@ -514,6 +545,7 @@ func setupCRDAndVerifySchema(f *framework.Framework, schema, expect []byte, grou
 		}
 		crd.Spec.Versions = apiVersions
 	})
+	crd, err := crd.CreateMultiVersionTestCRD(f, group, options...)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create CRD: %v", err)
 	}
@@ -728,6 +760,18 @@ properties:
               pattern: in-tree|out-of-tree
               type: string`)
 
+var schemaCustomService = []byte(`description: CustomService CRD for Testing
+type: object
+properties:
+  spec:
+    description: Specification of CustomService
+    type: object
+    properties:
+      dummy:
+        description: Dummy property.
+        type: string
+`)
+
 var schemaWaldo = []byte(`description: Waldo CRD for Testing
 type: object
 properties: