Merge pull request #120707 from Jefftree/csa-openapiv3

Use OpenAPI V3 for client side SMP

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/meta.go

@@ -20,12 +20,17 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"strings"
 
 	"k8s.io/apimachinery/pkg/util/mergepatch"
 	forkedjson "k8s.io/apimachinery/third_party/forked/golang/json"
 	openapi "k8s.io/kube-openapi/pkg/util/proto"
+	"k8s.io/kube-openapi/pkg/validation/spec"
 )
 
+const patchMergeKey = "x-kubernetes-patch-merge-key"
+const patchStrategy = "x-kubernetes-patch-strategy"
+
 type PatchMeta struct {
 	patchStrategies []string
 	patchMergeKey   string
@@ -148,6 +153,90 @@ func GetTagStructTypeOrDie(dataStruct interface{}) reflect.Type {
 	return t
 }
 
+type PatchMetaFromOpenAPIV3 struct {
+	// SchemaList is required to resolve OpenAPI V3 references
+	SchemaList map[string]*spec.Schema
+	Schema     *spec.Schema
+}
+
+func (s PatchMetaFromOpenAPIV3) traverse(key string) (PatchMetaFromOpenAPIV3, error) {
+	if s.Schema == nil {
+		return PatchMetaFromOpenAPIV3{}, nil
+	}
+	if len(s.Schema.Properties) == 0 {
+		return PatchMetaFromOpenAPIV3{}, fmt.Errorf("unable to find api field \"%s\"", key)
+	}
+	subschema, ok := s.Schema.Properties[key]
+	if !ok {
+		return PatchMetaFromOpenAPIV3{}, fmt.Errorf("unable to find api field \"%s\"", key)
+	}
+	return PatchMetaFromOpenAPIV3{SchemaList: s.SchemaList, Schema: &subschema}, nil
+}
+
+func resolve(l *PatchMetaFromOpenAPIV3) error {
+	if len(l.Schema.AllOf) > 0 {
+		l.Schema = &l.Schema.AllOf[0]
+	}
+	if refString := l.Schema.Ref.String(); refString != "" {
+		str := strings.TrimPrefix(refString, "#/components/schemas/")
+		sch, ok := l.SchemaList[str]
+		if ok {
+			l.Schema = sch
+		} else {
+			return fmt.Errorf("unable to resolve %s in OpenAPI V3", refString)
+		}
+	}
+	return nil
+}
+
+func (s PatchMetaFromOpenAPIV3) LookupPatchMetadataForStruct(key string) (LookupPatchMeta, PatchMeta, error) {
+	l, err := s.traverse(key)
+	if err != nil {
+		return l, PatchMeta{}, err
+	}
+	p := PatchMeta{}
+	f, ok := l.Schema.Extensions[patchMergeKey]
+	if ok {
+		p.SetPatchMergeKey(f.(string))
+	}
+	g, ok := l.Schema.Extensions[patchStrategy]
+	if ok {
+		p.SetPatchStrategies(strings.Split(g.(string), ","))
+	}
+
+	err = resolve(&l)
+	return l, p, err
+}
+
+func (s PatchMetaFromOpenAPIV3) LookupPatchMetadataForSlice(key string) (LookupPatchMeta, PatchMeta, error) {
+	l, err := s.traverse(key)
+	if err != nil {
+		return l, PatchMeta{}, err
+	}
+	p := PatchMeta{}
+	f, ok := l.Schema.Extensions[patchMergeKey]
+	if ok {
+		p.SetPatchMergeKey(f.(string))
+	}
+	g, ok := l.Schema.Extensions[patchStrategy]
+	if ok {
+		p.SetPatchStrategies(strings.Split(g.(string), ","))
+	}
+	if l.Schema.Items != nil {
+		l.Schema = l.Schema.Items.Schema
+	}
+	err = resolve(&l)
+	return l, p, err
+}
+
+func (s PatchMetaFromOpenAPIV3) Name() string {
+	schema := s.Schema
+	if len(schema.Type) > 0 {
+		return strings.Join(schema.Type, "")
+	}
+	return "Struct"
+}
+
 type PatchMetaFromOpenAPI struct {
 	Schema openapi.Schema
 }

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/patch_test.go

@@ -36,6 +36,9 @@ import (
 var (
 	fakeMergeItemSchema     = sptest.Fake{Path: filepath.Join("testdata", "swagger-merge-item.json")}
 	fakePrecisionItemSchema = sptest.Fake{Path: filepath.Join("testdata", "swagger-precision-item.json")}
+
+	fakeMergeItemV3Schema     = sptest.OpenAPIV3Getter{Path: filepath.Join("testdata", "swagger-merge-item-v3.json")}
+	fakePrecisionItemV3Schema = sptest.OpenAPIV3Getter{Path: filepath.Join("testdata", "swagger-precision-item-v3.json")}
 )
 
 type SortMergeListTestCases struct {
@@ -284,9 +287,14 @@ func TestSortMergeLists(t *testing.T) {
 	mergeItemOpenapiSchema := PatchMetaFromOpenAPI{
 		Schema: sptest.GetSchemaOrDie(&fakeMergeItemSchema, "mergeItem"),
 	}
+	mergeItemOpenapiV3Schema := PatchMetaFromOpenAPIV3{
+		SchemaList: fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas,
+		Schema:     fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas["mergeItem"],
+	}
 	schemas := []LookupPatchMeta{
 		mergeItemStructSchema,
 		mergeItemOpenapiSchema,
+		mergeItemOpenapiV3Schema,
 	}
 
 	tc := SortMergeListTestCases{}
@@ -766,9 +774,14 @@ func TestCustomStrategicMergePatch(t *testing.T) {
 	mergeItemOpenapiSchema := PatchMetaFromOpenAPI{
 		Schema: sptest.GetSchemaOrDie(&fakeMergeItemSchema, "mergeItem"),
 	}
+	mergeItemOpenapiV3Schema := PatchMetaFromOpenAPIV3{
+		SchemaList: fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas,
+		Schema:     fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas["mergeItem"],
+	}
 	schemas := []LookupPatchMeta{
 		mergeItemStructSchema,
 		mergeItemOpenapiSchema,
+		mergeItemOpenapiV3Schema,
 	}
 
 	tc := StrategicMergePatchTestCases{}
@@ -6169,9 +6182,14 @@ func TestStrategicMergePatch(t *testing.T) {
 	mergeItemOpenapiSchema := PatchMetaFromOpenAPI{
 		Schema: sptest.GetSchemaOrDie(&fakeMergeItemSchema, "mergeItem"),
 	}
+	mergeItemOpenapiV3Schema := PatchMetaFromOpenAPIV3{
+		SchemaList: fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas,
+		Schema:     fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas["mergeItem"],
+	}
 	schemas := []LookupPatchMeta{
 		mergeItemStructSchema,
 		mergeItemOpenapiSchema,
+		mergeItemOpenapiV3Schema,
 	}
 
 	tc := StrategicMergePatchTestCases{}
@@ -6564,9 +6582,14 @@ func TestNumberConversion(t *testing.T) {
 	precisionItemOpenapiSchema := PatchMetaFromOpenAPI{
 		Schema: sptest.GetSchemaOrDie(&fakePrecisionItemSchema, "precisionItem"),
 	}
+	precisionItemOpenapiV3Schema := PatchMetaFromOpenAPIV3{
+		SchemaList: fakePrecisionItemV3Schema.SchemaOrDie().Components.Schemas,
+		Schema:     fakePrecisionItemV3Schema.SchemaOrDie().Components.Schemas["precisionItem"],
+	}
 	precisionItemSchemas := []LookupPatchMeta{
 		precisionItemStructSchema,
 		precisionItemOpenapiSchema,
+		precisionItemOpenapiV3Schema,
 	}
 
 	for _, schema := range precisionItemSchemas {
@@ -6774,9 +6797,14 @@ func TestReplaceWithRawExtension(t *testing.T) {
 	mergeItemOpenapiSchema := PatchMetaFromOpenAPI{
 		Schema: sptest.GetSchemaOrDie(&fakeMergeItemSchema, "mergeItem"),
 	}
+	mergeItemOpenapiV3Schema := PatchMetaFromOpenAPIV3{
+		SchemaList: fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas,
+		Schema:     fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas["mergeItem"],
+	}
 	schemas := []LookupPatchMeta{
 		mergeItemStructSchema,
 		mergeItemOpenapiSchema,
+		mergeItemOpenapiV3Schema,
 	}
 
 	for _, schema := range schemas {
@@ -6946,9 +6974,14 @@ func TestUnknownField(t *testing.T) {
 	mergeItemOpenapiSchema := PatchMetaFromOpenAPI{
 		Schema: sptest.GetSchemaOrDie(&fakeMergeItemSchema, "mergeItem"),
 	}
+	mergeItemOpenapiV3Schema := PatchMetaFromOpenAPIV3{
+		SchemaList: fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas,
+		Schema:     fakeMergeItemV3Schema.SchemaOrDie().Components.Schemas["mergeItem"],
+	}
 	schemas := []LookupPatchMeta{
 		mergeItemStructSchema,
 		mergeItemOpenapiSchema,
+		mergeItemOpenapiV3Schema,
 	}
 
 	for _, k := range sets.StringKeySet(testcases).List() {

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/testdata/swagger-merge-item-v3.json

@@ -0,0 +1,180 @@
+{
+  "openapi": "3.0",
+  "info": {
+    "title": "StrategicMergePatchTestingMergeItem",
+    "version": "v3.0"
+  },
+  "paths": {},
+  "components": {
+    "schemas": {
+      "mergeItem": {
+        "description": "MergeItem is type definition for testing strategic merge.",
+        "required": [],
+        "properties": {
+          "name": {
+            "description": "Name field.",
+            "type": "string"
+          },
+          "value": {
+            "description": "Value field.",
+            "type": "string"
+          },
+          "other": {
+            "description": "Other field.",
+            "type": "string"
+          },
+          "mergingList": {
+            "description": "MergingList field.",
+            "type": "array",
+            "items": {
+              "default": {},
+              "allOf": [
+                {"$ref": "#/components/schemas/mergeItem"}
+              ]
+            },
+            "x-kubernetes-patch-merge-key": "name",
+            "x-kubernetes-patch-strategy": "merge"
+          },
+          "nonMergingList": {
+            "description": "NonMergingList field.",
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/mergeItem"
+            }
+          },
+          "mergingIntList": {
+            "description": "MergingIntList field.",
+            "type": "array",
+            "items": {
+              "type": "integer",
+              "format": "int32"
+            },
+            "x-kubernetes-patch-strategy": "merge"
+          },
+          "nonMergingIntList": {
+            "description": "NonMergingIntList field.",
+            "type": "array",
+            "items": {
+              "type": "integer",
+              "format": "int32"
+            }
+          },
+          "mergeItemPtr": {
+            "description": "MergeItemPtr field.",
+            "allOf": [
+              {"$ref": "#/components/schemas/mergeItem"}
+            ],
+            "x-kubernetes-patch-merge-key": "name",
+            "x-kubernetes-patch-strategy": "merge"
+          },
+          "simpleMap": {
+            "description": "SimpleMap field.",
+            "type": "object",
+            "additionalProperties": {
+              "type": "string"
+            }
+          },
+          "replacingItem": {
+            "description": "ReplacingItem field.",
+            "allOf": [
+              {"$ref": "#/components/schemas/io.k8s.apimachinery.pkg.runtime.RawExtension"}
+            ],
+            "x-kubernetes-patch-strategy": "replace"
+          },
+          "retainKeysMap": {
+            "description": "RetainKeysMap field.",
+            "allOf": [
+              {"$ref": "#/components/schemas/retainKeysMergeItem"}
+            ],
+            "x-kubernetes-patch-strategy": "retainKeys"
+          },
+          "retainKeysMergingList": {
+            "description": "RetainKeysMergingList field.",
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/mergeItem"
+            },
+            "x-kubernetes-patch-merge-key": "name",
+            "x-kubernetes-patch-strategy": "merge,retainKeys"
+          }
+        },
+        "x-kubernetes-group-version-kind": [
+          {
+            "group": "fake-group",
+            "kind": "mergeItem",
+            "version": "some-version"
+          }
+        ]
+      },
+      "retainKeysMergeItem": {
+        "description": "RetainKeysMergeItem is type definition for testing strategic merge.",
+        "required": [],
+        "properties": {
+          "name": {
+            "description": "Name field.",
+            "type": "string"
+          },
+          "value": {
+            "description": "Value field.",
+            "type": "string"
+          },
+          "other": {
+            "description": "Other field.",
+            "type": "string"
+          },
+          "simpleMap": {
+            "description": "SimpleMap field.",
+            "items": {
+              "type": "string"
+            }
+          },
+          "mergingList": {
+            "description": "MergingList field.",
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/mergeItem"
+            },
+            "x-kubernetes-patch-merge-key": "name",
+            "x-kubernetes-patch-strategy": "merge"
+          },
+          "nonMergingList": {
+            "description": "NonMergingList field.",
+            "type": "array",
+            "items": {
+              "$ref": "#/components/schemas/mergeItem"
+            }
+          },
+          "mergingIntList": {
+            "description": "MergingIntList field.",
+            "type": "array",
+            "items": {
+              "type": "integer",
+              "format": "int32"
+            },
+            "x-kubernetes-patch-strategy": "merge"
+          }
+        },
+        "x-kubernetes-group-version-kind": [
+          {
+            "group": "fake-group",
+            "kind": "retainKeysMergeItem",
+            "version": "some-version"
+          }
+        ]
+      },
+      "io.k8s.apimachinery.pkg.runtime.RawExtension": {
+        "description": "RawExtension is used to hold extensions in external versions.",
+        "required": [
+          "Raw"
+        ],
+        "properties": {
+          "Raw": {
+            "description": "Raw is the underlying serialization of this object.",
+            "type": "string",
+            "format": "byte"
+          }
+        }
+      }
+    }
+  }
+}

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/testdata/swagger-precision-item-v3.json

@@ -0,0 +1,49 @@
+{
+  "openapi": "3.0",
+  "info": {
+    "title": "StrategicMergePatchTestingPrecisionItem",
+    "version": "v1.9.0"
+  },
+  "paths": {},
+  "components": {
+    "schemas": {
+      "precisionItem": {
+        "description": "PrecisionItem is type definition for testing strategic merge.",
+        "required": [],
+        "properties": {
+          "name": {
+            "description": "Name field.",
+            "type": "string"
+          },
+          "int32": {
+            "description": "Int32 field.",
+            "type": "integer",
+            "format": "int32"
+          },
+          "int64": {
+            "description": "Int64 field.",
+            "type": "integer",
+            "format": "int64"
+          },
+          "float32": {
+            "description": "Float32 field.",
+            "type": "number",
+            "format": "float32"
+          },
+          "float64": {
+            "description": "Float64 field.",
+            "type": "number",
+            "format": "float64"
+          }
+        },
+        "x-kubernetes-group-version-kind": [
+          {
+            "group": "fake-group",
+            "kind": "precisionItem",
+            "version": "some-version"
+          }
+        ]
+      }
+    }
+  }
+}

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/testing/openapi3.go

@@ -0,0 +1,65 @@
+/*
+Copyright 2023 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package testing
+
+import (
+	"os"
+	"sync"
+
+	"k8s.io/kube-openapi/pkg/spec3"
+)
+
+type OpenAPIV3Getter struct {
+	Path      string
+	once      sync.Once
+	bytes     []byte
+	openapiv3 spec3.OpenAPI
+}
+
+func (f *OpenAPIV3Getter) SchemaBytesOrDie() []byte {
+	f.once.Do(func() {
+		_, err := os.Stat(f.Path)
+		if err != nil {
+			panic(err)
+		}
+		spec, err := os.ReadFile(f.Path)
+		if err != nil {
+			panic(err)
+		}
+		f.bytes = spec
+	})
+	return f.bytes
+}
+
+func (f *OpenAPIV3Getter) SchemaOrDie() *spec3.OpenAPI {
+	f.once.Do(func() {
+		_, err := os.Stat(f.Path)
+		if err != nil {
+			panic(err)
+		}
+		spec, err := os.ReadFile(f.Path)
+		if err != nil {
+			panic(err)
+		}
+
+		err = f.openapiv3.UnmarshalJSON(spec)
+		if err != nil {
+			panic(err)
+		}
+	})
+	return &f.openapiv3
+}

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

@@ -39,6 +39,7 @@ import (
 	"k8s.io/cli-runtime/pkg/printers"
 	"k8s.io/cli-runtime/pkg/resource"
 	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/openapi3"
 	"k8s.io/client-go/util/csaupgrade"
 	"k8s.io/component-base/version"
 	"k8s.io/klog/v2"
@@ -105,7 +106,8 @@ type ApplyOptions struct {
 	Builder             *resource.Builder
 	Mapper              meta.RESTMapper
 	DynamicClient       dynamic.Interface
-	OpenAPISchema       openapi.Resources
+	OpenAPIGetter       openapi.OpenAPIResourcesGetter
+	OpenAPIV3Root       openapi3.Root
 
 	Namespace        string
 	EnforceNamespace bool
@@ -282,7 +284,15 @@ func (flags *ApplyFlags) ToOptions(f cmdutil.Factory, cmd *cobra.Command, baseNa
 		return nil, err
 	}
 
-	openAPISchema, _ := f.OpenAPISchema()
+	var openAPIV3Root openapi3.Root
+	if !cmdutil.OpenAPIV3Patch.IsDisabled() {
+		openAPIV3Client, err := f.OpenAPIV3Client()
+		if err == nil {
+			openAPIV3Root = openapi3.NewRoot(openAPIV3Client)
+		} else {
+			klog.V(4).Infof("warning: OpenAPI V3 Patch is enabled but is unable to be loaded. Will fall back to OpenAPI V2")
+		}
+	}
 
 	validationDirective, err := cmdutil.GetValidationDirective(cmd)
 	if err != nil {
@@ -360,7 +370,8 @@ func (flags *ApplyFlags) ToOptions(f cmdutil.Factory, cmd *cobra.Command, baseNa
 		Builder:             builder,
 		Mapper:              mapper,
 		DynamicClient:       dynamicClient,
-		OpenAPISchema:       openAPISchema,
+		OpenAPIGetter:       f,
+		OpenAPIV3Root:       openAPIV3Root,
 
 		IOStreams: flags.IOStreams,
 

staging/src/k8s.io/kubectl/pkg/cmd/apply/patcher.go

@@ -37,6 +37,9 @@ import (
 	"k8s.io/apimachinery/pkg/util/strategicpatch"
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/cli-runtime/pkg/resource"
+	"k8s.io/client-go/openapi3"
+	"k8s.io/klog/v2"
+	"k8s.io/kube-openapi/pkg/validation/spec"
 	cmdutil "k8s.io/kubectl/pkg/cmd/util"
 	"k8s.io/kubectl/pkg/scheme"
 	"k8s.io/kubectl/pkg/util"
@@ -50,6 +53,10 @@ const (
 	backOffPeriod = 1 * time.Second
 	// how many times we can retry before back off
 	triesBeforeBackOff = 1
+	// groupVersionKindExtensionKey is the key used to lookup the
+	// GroupVersionKind value for an object definition from the
+	// definition's "extensions" map.
+	groupVersionKindExtensionKey = "x-kubernetes-group-version-kind"
 )
 
 var createPatchErrFormat = "creating patch with:\noriginal:\n%s\nmodified:\n%s\ncurrent:\n%s\nfor:"
@@ -73,13 +80,17 @@ type Patcher struct {
 	// Number of retries to make if the patch fails with conflict
 	Retries int
 
-	OpenapiSchema openapi.Resources
+	OpenAPIGetter openapi.OpenAPIResourcesGetter
+	OpenAPIV3Root openapi3.Root
 }
 
 func newPatcher(o *ApplyOptions, info *resource.Info, helper *resource.Helper) (*Patcher, error) {
-	var openapiSchema openapi.Resources
+	var openAPIGetter openapi.OpenAPIResourcesGetter
+	var openAPIV3Root openapi3.Root
+
 	if o.OpenAPIPatch {
-		openapiSchema = o.OpenAPISchema
+		openAPIGetter = o.OpenAPIGetter
+		openAPIV3Root = o.OpenAPIV3Root
 	}
 
 	return &Patcher{
@@ -91,7 +102,8 @@ func newPatcher(o *ApplyOptions, info *resource.Info, helper *resource.Helper) (
 		CascadingStrategy: o.DeleteOptions.CascadingStrategy,
 		Timeout:           o.DeleteOptions.Timeout,
 		GracePeriod:       o.DeleteOptions.GracePeriod,
-		OpenapiSchema:     openapiSchema,
+		OpenAPIGetter:     openAPIGetter,
+		OpenAPIV3Root:     openAPIV3Root,
 		Retries:           maxPatchRetry,
 	}, nil
 }
@@ -118,14 +130,42 @@ func (p *Patcher) patchSimple(obj runtime.Object, modified []byte, namespace, na
 	var patchType types.PatchType
 	var patch []byte
 
-	if p.OpenapiSchema != nil {
-		// if openapischema is used, we'll try to get required patch type for this GVK from Open API.
-		// if it fails or could not find any patch type, fall back to baked-in patch type determination.
-		if patchType, err = p.getPatchTypeFromOpenAPI(p.Mapping.GroupVersionKind); err == nil && patchType == types.StrategicMergePatchType {
-			patch, err = p.buildStrategicMergeFromOpenAPI(original, modified, current)
+	if p.OpenAPIV3Root != nil {
+		gvkSupported, err := p.gvkSupportsPatchOpenAPIV3(p.Mapping.GroupVersionKind)
+		if err != nil {
+			// Realistically this error logging is not needed (not present in V2),
+			// but would help us in debugging if users encounter a problem
+			// with OpenAPI V3 not present in V2.
+			klog.V(5).Infof("warning: OpenAPI V3 path does not exist - group: %s, version %s, kind %s\n",
+				p.Mapping.GroupVersionKind.Group, p.Mapping.GroupVersionKind.Version, p.Mapping.GroupVersionKind.Kind)
+		} else if gvkSupported {
+			patch, err = p.buildStrategicMergePatchFromOpenAPIV3(original, modified, current)
 			if err != nil {
-				// Warn user about problem and continue strategic merge patching using builtin types.
-				fmt.Fprintf(errOut, "warning: error calculating patch from openapi spec: %v\n", err)
+				// Fall back to OpenAPI V2 if there is a problem
+				// We should remove the fallback in the future,
+				// but for the first release it might be beneficial
+				// to fall back to OpenAPI V2 while logging the error
+				// and seeing if we get any bug reports.
+				fmt.Fprintf(errOut, "warning: error calculating patch from openapi v3 spec: %v\n", err)
+			} else {
+				patchType = types.StrategicMergePatchType
+			}
+		} else {
+			klog.V(5).Infof("warning: OpenAPI V3 path does not support strategic merge patch - group: %s, version %s, kind %s\n",
+				p.Mapping.GroupVersionKind.Group, p.Mapping.GroupVersionKind.Version, p.Mapping.GroupVersionKind.Kind)
+		}
+	}
+
+	if patch == nil {
+		if openAPISchema, err := p.OpenAPIGetter.OpenAPISchema(); err == nil && openAPISchema != nil {
+			// if openapischema is used, we'll try to get required patch type for this GVK from Open API.
+			// if it fails or could not find any patch type, fall back to baked-in patch type determination.
+			if patchType, err = p.getPatchTypeFromOpenAPI(openAPISchema, p.Mapping.GroupVersionKind); err == nil && patchType == types.StrategicMergePatchType {
+				patch, err = p.buildStrategicMergeFromOpenAPI(openAPISchema, original, modified, current)
+				if err != nil {
+					// Warn user about problem and continue strategic merge patching using builtin types.
+					fmt.Fprintf(errOut, "warning: error calculating patch from openapi spec: %v\n", err)
+				}
 			}
 		}
 	}
@@ -182,10 +222,94 @@ func (p *Patcher) buildMergePatch(original, modified, current []byte) ([]byte, e
 	return patch, nil
 }
 
+// gvkSupportsPatchOpenAPIV3 checks if a particular GVK supports the patch operation.
+// It returns an error if the OpenAPI V3 could not be downloaded.
+func (p *Patcher) gvkSupportsPatchOpenAPIV3(gvk schema.GroupVersionKind) (bool, error) {
+	gvSpec, err := p.OpenAPIV3Root.GVSpec(schema.GroupVersion{
+		Group:   p.Mapping.GroupVersionKind.Group,
+		Version: p.Mapping.GroupVersionKind.Version,
+	})
+	if err != nil {
+		return false, err
+	}
+	if gvSpec == nil || gvSpec.Paths == nil || gvSpec.Paths.Paths == nil {
+		return false, fmt.Errorf("gvk group: %s, version: %s, kind: %s does not exist for OpenAPI V3", gvk.Group, gvk.Version, gvk.Kind)
+	}
+	for _, path := range gvSpec.Paths.Paths {
+		if path.Patch != nil {
+			if gvkMatchesSingle(p.Mapping.GroupVersionKind, path.Patch.Extensions) {
+				if path.Patch.RequestBody == nil || path.Patch.RequestBody.Content == nil {
+					// GVK exists but does not support requestBody. Indication of malformed OpenAPI.
+					return false, nil
+				}
+				if _, ok := path.Patch.RequestBody.Content["application/strategic-merge-patch+json"]; ok {
+					return true, nil
+				}
+				// GVK exists but strategic-merge-patch is not supported. Likely to be a CRD or aggregated resource.
+				return false, nil
+			}
+		}
+	}
+	return false, nil
+}
+
+func gvkMatchesArray(targetGVK schema.GroupVersionKind, ext spec.Extensions) bool {
+	var gvkList []map[string]string
+	err := ext.GetObject(groupVersionKindExtensionKey, &gvkList)
+	if err != nil {
+		return false
+	}
+	for _, gvkMap := range gvkList {
+		if gvkMap["group"] == targetGVK.Group &&
+			gvkMap["version"] == targetGVK.Version &&
+			gvkMap["kind"] == targetGVK.Kind {
+			return true
+		}
+	}
+	return false
+}
+
+func gvkMatchesSingle(targetGVK schema.GroupVersionKind, ext spec.Extensions) bool {
+	var gvkMap map[string]string
+	err := ext.GetObject(groupVersionKindExtensionKey, &gvkMap)
+	if err != nil {
+		return false
+	}
+	return gvkMap["group"] == targetGVK.Group &&
+		gvkMap["version"] == targetGVK.Version &&
+		gvkMap["kind"] == targetGVK.Kind
+}
+
+func (p *Patcher) buildStrategicMergePatchFromOpenAPIV3(original, modified, current []byte) ([]byte, error) {
+	gvSpec, err := p.OpenAPIV3Root.GVSpec(schema.GroupVersion{
+		Group:   p.Mapping.GroupVersionKind.Group,
+		Version: p.Mapping.GroupVersionKind.Version,
+	})
+	if err != nil {
+		return nil, err
+	}
+	if gvSpec == nil || gvSpec.Components == nil {
+		return nil, fmt.Errorf("OpenAPI V3 Components is nil")
+	}
+	for _, c := range gvSpec.Components.Schemas {
+		if !gvkMatchesArray(p.Mapping.GroupVersionKind, c.Extensions) {
+			continue
+		}
+		lookupPatchMeta := strategicpatch.PatchMetaFromOpenAPIV3{Schema: c, SchemaList: gvSpec.Components.Schemas}
+		if openapiv3Patch, err := strategicpatch.CreateThreeWayMergePatch(original, modified, current, lookupPatchMeta, p.Overwrite); err != nil {
+			return nil, err
+		} else {
+			return openapiv3Patch, nil
+		}
+
+	}
+	return nil, nil
+}
+
 // buildStrategicMergeFromOpenAPI builds patch from OpenAPI if it is enabled.
 // This is used for core types which is published in openapi.
-func (p *Patcher) buildStrategicMergeFromOpenAPI(original, modified, current []byte) ([]byte, error) {
-	schema := p.OpenapiSchema.LookupResource(p.Mapping.GroupVersionKind)
+func (p *Patcher) buildStrategicMergeFromOpenAPI(openAPISchema openapi.Resources, original, modified, current []byte) ([]byte, error) {
+	schema := openAPISchema.LookupResource(p.Mapping.GroupVersionKind)
 	if schema == nil {
 		// Missing schema returns nil patch; also no error.
 		return nil, nil
@@ -199,8 +323,8 @@ func (p *Patcher) buildStrategicMergeFromOpenAPI(original, modified, current []b
 }
 
 // getPatchTypeFromOpenAPI looks up patch types supported by given GroupVersionKind in Open API.
-func (p *Patcher) getPatchTypeFromOpenAPI(gvk schema.GroupVersionKind) (types.PatchType, error) {
-	if pc := p.OpenapiSchema.GetConsumes(p.Mapping.GroupVersionKind, "PATCH"); pc != nil {
+func (p *Patcher) getPatchTypeFromOpenAPI(openAPISchema openapi.Resources, gvk schema.GroupVersionKind) (types.PatchType, error) {
+	if pc := openAPISchema.GetConsumes(p.Mapping.GroupVersionKind, "PATCH"); pc != nil {
 		for _, c := range pc {
 			if c == string(types.StrategicMergePatchType) {
 				return types.StrategicMergePatchType, nil

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

@@ -35,6 +35,7 @@ import (
 	"k8s.io/cli-runtime/pkg/genericiooptions"
 	"k8s.io/cli-runtime/pkg/resource"
 	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/openapi3"
 	"k8s.io/klog/v2"
 	"k8s.io/kubectl/pkg/cmd/apply"
 	cmdutil "k8s.io/kubectl/pkg/cmd/util"
@@ -109,7 +110,8 @@ type DiffOptions struct {
 
 	Concurrency      int
 	Selector         string
-	OpenAPISchema    openapi.Resources
+	OpenAPIGetter    openapi.OpenAPIResourcesGetter
+	OpenAPIV3Root    openapi3.Root
 	DynamicClient    dynamic.Interface
 	CmdNamespace     string
 	EnforceNamespace bool
@@ -323,7 +325,8 @@ type InfoObject struct {
 	LocalObj        runtime.Object
 	Info            *resource.Info
 	Encoder         runtime.Encoder
-	OpenAPI         openapi.Resources
+	OpenAPIGetter   openapi.OpenAPIResourcesGetter
+	OpenAPIV3Root   openapi3.Root
 	Force           bool
 	ServerSideApply bool
 	FieldManager    string
@@ -395,7 +398,8 @@ func (obj InfoObject) Merged() (runtime.Object, error) {
 		Helper:          helper,
 		Overwrite:       true,
 		BackOff:         clockwork.NewRealClock(),
-		OpenapiSchema:   obj.OpenAPI,
+		OpenAPIGetter:   obj.OpenAPIGetter,
+		OpenAPIV3Root:   obj.OpenAPIV3Root,
 		ResourceVersion: resourceVersion,
 	}
 
@@ -637,9 +641,14 @@ func (o *DiffOptions) Complete(f cmdutil.Factory, cmd *cobra.Command, args []str
 	}
 
 	if !o.ServerSideApply {
-		o.OpenAPISchema, err = f.OpenAPISchema()
-		if err != nil {
-			return err
+		o.OpenAPIGetter = f
+		if !cmdutil.OpenAPIV3Patch.IsDisabled() {
+			openAPIV3Client, err := f.OpenAPIV3Client()
+			if err == nil {
+				o.OpenAPIV3Root = openapi3.NewRoot(openAPIV3Client)
+			} else {
+				klog.V(4).Infof("warning: OpenAPI V3 Patch is enabled but is unable to be loaded. Will fall back to OpenAPI V2")
+			}
 		}
 	}
 
@@ -721,7 +730,8 @@ func (o *DiffOptions) Run() error {
 				LocalObj:        local,
 				Info:            info,
 				Encoder:         scheme.DefaultJSONEncoder(),
-				OpenAPI:         o.OpenAPISchema,
+				OpenAPIGetter:   o.OpenAPIGetter,
+				OpenAPIV3Root:   o.OpenAPIV3Root,
 				Force:           force,
 				ServerSideApply: o.ServerSideApply,
 				FieldManager:    o.FieldManager,

staging/src/k8s.io/kubectl/pkg/cmd/testing/util.go

@@ -195,3 +195,18 @@ func WithAlphaEnvs(features []cmdutil.FeatureGate, t *testing.T, f func(*testing
 	}
 	f(t)
 }
+
+// WithAlphaEnvs calls func f with the given env-var-based feature gates disabled,
+// and then restores the original values of those variables.
+func WithAlphaEnvsDisabled(features []cmdutil.FeatureGate, t *testing.T, f func(*testing.T)) {
+	for _, feature := range features {
+		key := string(feature)
+		if key != "" {
+			oldValue := os.Getenv(key)
+			err := os.Setenv(key, "false")
+			require.NoError(t, err, "unexpected error setting alpha env")
+			defer os.Setenv(key, oldValue)
+		}
+	}
+	f(t)
+}

staging/src/k8s.io/kubectl/pkg/cmd/util/factory_client_access.go

@@ -214,5 +214,5 @@ func (f *factoryImpl) OpenAPIV3Client() (openapiclient.Client, error) {
 		return nil, err
 	}
 
-	return discovery.OpenAPIV3(), nil
+	return cached.NewClient(discovery.OpenAPIV3()), nil
 }

staging/src/k8s.io/kubectl/pkg/cmd/util/helpers.go

@@ -428,6 +428,7 @@ const (
 	ApplySet                FeatureGate = "KUBECTL_APPLYSET"
 	CmdPluginAsSubcommand   FeatureGate = "KUBECTL_ENABLE_CMD_SHADOW"
 	InteractiveDelete       FeatureGate = "KUBECTL_INTERACTIVE_DELETE"
+	OpenAPIV3Patch          FeatureGate = "KUBECTL_OPENAPIV3_PATCH"
 	RemoteCommandWebsockets FeatureGate = "KUBECTL_REMOTE_COMMAND_WEBSOCKETS"
 )