Feat: add support for json-patch and json-merge-patch (#3406)

* Feat: add support for json-patch and json-merge-patch

Signed-off-by: Somefive <yd219913@alibaba-inc.com>

* Fix: add e2e test

Signed-off-by: Somefive <yd219913@alibaba-inc.com>

* Fix: refactor json-patch field

Signed-off-by: Somefive <yd219913@alibaba-inc.com>

charts/vela-core/templates/defwithtemplate/json-merge-patch.yaml

@@ -1,11 +1,11 @@
 # Code generated by KubeVela templates. DO NOT EDIT. Please edit the original cue file.
-# Definition source cue file: vela-templates/definitions/internal/patch.cue
+# Definition source cue file: vela-templates/definitions/internal/json-merge-patch.cue
 apiVersion: core.oam.dev/v1beta1
 kind: TraitDefinition
 metadata:
   annotations:
-    definition.oam.dev/description: Patch the output directly.
-  name: patch
+    definition.oam.dev/description: Patch the output following Json Merge Patch strategy, following RFC 7396.
+  name: json-merge-patch
   namespace: {{ include "systemDefinitionNamespace" . }}
 spec:
   appliesToWorkloads:
@@ -15,6 +15,6 @@ spec:
     cue:
       template: |
         parameter: {...}
-        // +patchStrategy=open
+        // +patchStrategy=jsonMergePatch
         patch: parameter
 

charts/vela-core/templates/defwithtemplate/json-patch.yaml

@@ -0,0 +1,20 @@
+# Code generated by KubeVela templates. DO NOT EDIT. Please edit the original cue file.
+# Definition source cue file: vela-templates/definitions/internal/json-patch.cue
+apiVersion: core.oam.dev/v1beta1
+kind: TraitDefinition
+metadata:
+  annotations:
+    definition.oam.dev/description: Patch the output following Json Patch strategy, following RFC 6902.
+  name: json-patch
+  namespace: {{ include "systemDefinitionNamespace" . }}
+spec:
+  appliesToWorkloads:
+    - '*'
+  podDisruptive: true
+  schematic:
+    cue:
+      template: |
+        parameter: operations: [...{...}]
+        // +patchStrategy=jsonPatch
+        patch: parameter
+

charts/vela-minimal/templates/defwithtemplate/json-merge-patch.yaml

@@ -0,0 +1,20 @@
+# Code generated by KubeVela templates. DO NOT EDIT. Please edit the original cue file.
+# Definition source cue file: vela-templates/definitions/internal/json-merge-patch.cue
+apiVersion: core.oam.dev/v1beta1
+kind: TraitDefinition
+metadata:
+  annotations:
+    definition.oam.dev/description: Patch the output following Json Merge Patch strategy, following RFC 7396.
+  name: json-merge-patch
+  namespace: {{ include "systemDefinitionNamespace" . }}
+spec:
+  appliesToWorkloads:
+    - '*'
+  podDisruptive: true
+  schematic:
+    cue:
+      template: |
+        parameter: {...}
+        // +patchStrategy=jsonMergePatch
+        patch: parameter
+

charts/vela-minimal/templates/defwithtemplate/json-patch.yaml

@@ -0,0 +1,20 @@
+# Code generated by KubeVela templates. DO NOT EDIT. Please edit the original cue file.
+# Definition source cue file: vela-templates/definitions/internal/json-patch.cue
+apiVersion: core.oam.dev/v1beta1
+kind: TraitDefinition
+metadata:
+  annotations:
+    definition.oam.dev/description: Patch the output following Json Patch strategy, following RFC 6902.
+  name: json-patch
+  namespace: {{ include "systemDefinitionNamespace" . }}
+spec:
+  appliesToWorkloads:
+    - '*'
+  podDisruptive: true
+  schematic:
+    cue:
+      template: |
+        parameter: operations: [...{...}]
+        // +patchStrategy=jsonPatch
+        patch: parameter
+

docs/examples/traits/json-merge-patch/example.yaml

@@ -0,0 +1,39 @@
+apiVersion: core.oam.dev/v1beta1
+kind: Application
+metadata:
+  name: busybox
+spec:
+  components:
+    - name: busybox
+      type: webservice
+      properties:
+        image: busybox
+        cmd: ["sleep", "86400"]
+        labels:
+          pod-label-key: pod-label-value
+          to-delete-label-key: to-delete-label-value
+      traits:
+        # the json merge patch can be used to add, replace and delete fields
+        # the following part will
+        # 1. add `deploy-label-key` to deployment labels
+        # 2. set deployment replicas to 3
+        # 3. set `pod-label-key` to `pod-label-modified-value` in pod labels
+        # 4. delete `to-delete-label-key` in pod labels
+        # 5. reset `containers` for pod
+        - type: json-merge-patch
+          properties:
+            metadata:
+              labels:
+                deploy-label-key: deploy-label-added-value
+            spec:
+              replicas: 3
+              template:
+                metadata:
+                  labels:
+                    pod-label-key: pod-label-modified-value
+                    to-delete-label-key: null
+                spec:
+                  containers:
+                    - name: busybox-new
+                      image: busybox:1.34
+                      command: ["sleep", "864000"]

docs/examples/traits/json-patch/example.yaml

@@ -0,0 +1,44 @@
+apiVersion: core.oam.dev/v1beta1
+kind: Application
+metadata:
+  name: busybox
+spec:
+  components:
+    - name: busybox
+      type: webservice
+      properties:
+        image: busybox
+        cmd: ["sleep", "86400"]
+        labels:
+          pod-label-key: pod-label-value
+          to-delete-label-key: to-delete-label-value
+      traits:
+        # the json patch can be used to add, replace and delete fields
+        # the following part will
+        # 1. add `deploy-label-key` to deployment labels
+        # 2. set deployment replicas to 3
+        # 3. set `pod-label-key` to `pod-label-modified-value` in pod labels
+        # 4. delete `to-delete-label-key` in pod labels
+        # 5. add sidecar container for pod
+        - type: json-patch
+          properties:
+            operations:
+              - op: add
+                path: "/metadata"
+                value:
+                  labels:
+                    deploy-label-key: deploy-label-added-value
+              - op: add
+                path: "/spec/replicas"
+                value: 3
+              - op: replace
+                path: "/spec/template/metadata/labels/pod-label-key"
+                value: pod-label-modified-value
+              - op: remove
+                path: "/spec/template/metadata/labels/to-delete-label-key"
+              - op: add
+                path: "/spec/template/spec/containers/1"
+                value:
+                  name: busybox-sidecar
+                  image: busybox:1.34
+                  command: ["sleep", "864000"]

pkg/cue/definition/template.go

@@ -350,12 +350,7 @@ func (td *traitDef) Complete(ctx process.Context, abstractTemplate string, param
 		if err != nil {
 			return errors.WithMessagef(err, "invalid patch of trait %s", td.name)
 		}
-		if sets.IsOpenPatch(patcher) {
-			if err := base.Open(); err != nil {
-				return errors.WithMessagef(err, "cannot convert base to open struct")
-			}
-		}
-		if err := base.Unify(p); err != nil {
+		if err := base.Unify(p, sets.CreateUnifyOptionsForPatcher(patcher)...); err != nil {
 			return errors.WithMessagef(err, "invalid patch trait %s into workload", td.name)
 		}
 

pkg/cue/definition/template_test.go

@@ -369,15 +369,18 @@ parameter: {
 				},
 			},
 		},
-		"patch trait with open merge": {
+		"patch trait with json merge patch": {
 			traitTemplate: `
 parameter: {...}
-// +patchStrategy=open
+// +patchStrategy=jsonMergePatch
 patch: parameter
 `,
 			params: map[string]interface{}{
 				"spec": map[string]interface{}{
 					"replicas": 5,
+					"template": map[string]interface{}{
+						"spec": nil,
+					},
 				},
 			},
 			expWorkload: &unstructured.Unstructured{
@@ -392,16 +395,7 @@ patch: parameter
 						"template": map[string]interface{}{
 							"metadata": map[string]interface{}{
 								"labels": map[string]interface{}{"app.oam.dev/component": "test"},
-							},
-							"spec": map[string]interface{}{
-								"containers": []interface{}{map[string]interface{}{
-									"envFrom": []interface{}{map[string]interface{}{
-										"configMapRef": map[string]interface{}{"name": "testgame-config"},
-									}},
-									"image": "website:0.1",
-									"name":  "main",
-									"ports": []interface{}{map[string]interface{}{"containerPort": int64(443)}}},
-								}}}}},
+							}}}},
 			},
 			expAssObjs: map[string]runtime.Object{
 				"AuxiliaryWorkloadgameconfig": &unstructured.Unstructured{
@@ -412,6 +406,54 @@ patch: parameter
 				},
 			},
 		},
+		"patch trait with json patch": {
+			traitTemplate: `
+parameter: {operations: [...{...}]}
+// +patchStrategy=jsonPatch
+patch: parameter
+`,
+			params: map[string]interface{}{
+				"operations": []map[string]interface{}{
+					{"op": "replace", "path": "/spec/replicas", "value": 5},
+					{"op": "remove", "path": "/spec/template/spec"},
+				},
+			},
+			expWorkload: &unstructured.Unstructured{
+				Object: map[string]interface{}{
+					"apiVersion": "apps/v1",
+					"kind":       "Deployment",
+					"spec": map[string]interface{}{
+						"replicas": int64(5),
+						"selector": map[string]interface{}{
+							"matchLabels": map[string]interface{}{
+								"app.oam.dev/component": "test"}},
+						"template": map[string]interface{}{
+							"metadata": map[string]interface{}{
+								"labels": map[string]interface{}{"app.oam.dev/component": "test"},
+							}}}},
+			},
+			expAssObjs: map[string]runtime.Object{
+				"AuxiliaryWorkloadgameconfig": &unstructured.Unstructured{
+					Object: map[string]interface{}{
+						"apiVersion": "v1",
+						"kind":       "ConfigMap",
+						"metadata":   map[string]interface{}{"name": "testgame-config"}, "data": map[string]interface{}{"enemies": "enemies-data", "lives": "lives-data"}},
+				},
+			},
+		},
+		"patch trait with invalid json patch": {
+			traitTemplate: `
+parameter: {patch: [...{...}]}
+// +patchStrategy=jsonPatch
+patch: parameter
+`,
+			params: map[string]interface{}{
+				"patch": []map[string]interface{}{
+					{"op": "what", "path": "/spec/replicas", "value": 5},
+				},
+			},
+			hasCompileErr: true,
+		},
 		"patch trait with replace": {
 			traitTemplate: `
 parameter: {

pkg/cue/model/instance.go

@@ -35,9 +35,8 @@ type Instance interface {
 	String() string
 	Unstructured() (*unstructured.Unstructured, error)
 	IsBase() bool
-	Unify(other Instance) error
+	Unify(other Instance, options ...sets.UnifyOption) error
 	Compile() ([]byte, error)
-	Open() error
 }
 
 type instance struct {
@@ -89,8 +88,8 @@ func (inst *instance) Unstructured() (*unstructured.Unstructured, error) {
 }
 
 // Unify implement unity operations between instances
-func (inst *instance) Unify(other Instance) error {
-	pv, err := sets.StrategyUnify(inst.v, other.String())
+func (inst *instance) Unify(other Instance, options ...sets.UnifyOption) error {
+	pv, err := sets.StrategyUnify(inst.v, other.String(), options...)
 	if err != nil {
 		return err
 	}
@@ -98,16 +97,6 @@ func (inst *instance) Unify(other Instance) error {
 	return nil
 }
 
-// Open convert instance value to open
-func (inst *instance) Open() error {
-	open, err := sets.OpenBaiscLit(inst.v)
-	if err != nil {
-		return err
-	}
-	inst.v = open
-	return nil
-}
-
 // NewBase create a base instance
 func NewBase(v cue.Value) (Instance, error) {
 	vs, err := openPrint(v)

pkg/cue/model/sets/operation.go

@@ -22,6 +22,7 @@ import (
 	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/parser"
+	jsonpatch "github.com/evanphx/json-patch"
 	"github.com/pkg/errors"
 )
 
@@ -33,16 +34,62 @@ const (
 
 	// StrategyRetainKeys notes on the strategic merge patch using the retainKeys strategy
 	StrategyRetainKeys = "retainKeys"
-	// StrategyOpen notes on the strategic merge patch will allow any merge
-	StrategyOpen = "open"
 	// StrategyReplace notes on the strategic merge patch will allow replacing list
 	StrategyReplace = "replace"
+	// StrategyJSONPatch notes on the strategic merge patch will follow the RFC 6902 to run JsonPatch
+	StrategyJSONPatch = "jsonPatch"
+	// StrategyJSONMergePatch notes on the strategic merge patch will follow the RFC 7396 to run JsonMergePatch
+	StrategyJSONMergePatch = "jsonMergePatch"
 )
 
 var (
 	notFoundErr = errors.Errorf("not found")
 )
 
+// UnifyParams params for unify
+type UnifyParams struct {
+	PatchStrategy string
+}
+
+// UnifyOption defines the option for unify
+type UnifyOption interface {
+	ApplyToOption(params *UnifyParams)
+}
+
+// UnifyByJSONPatch unify by json patch following RFC 6902
+type UnifyByJSONPatch struct{}
+
+// ApplyToOption apply to option
+func (op UnifyByJSONPatch) ApplyToOption(params *UnifyParams) {
+	params.PatchStrategy = StrategyJSONPatch
+}
+
+// UnifyByJSONMergePatch unify by json patch following RFC 7396
+type UnifyByJSONMergePatch struct{}
+
+// ApplyToOption apply to option
+func (op UnifyByJSONMergePatch) ApplyToOption(params *UnifyParams) {
+	params.PatchStrategy = StrategyJSONMergePatch
+}
+
+func newUnifyParams(options ...UnifyOption) *UnifyParams {
+	params := &UnifyParams{}
+	for _, op := range options {
+		op.ApplyToOption(params)
+	}
+	return params
+}
+
+// CreateUnifyOptionsForPatcher create unify options for patcher
+func CreateUnifyOptionsForPatcher(patcher cue.Value) (options []UnifyOption) {
+	if IsJSONPatch(patcher) {
+		options = append(options, UnifyByJSONPatch{})
+	} else if IsJSONMergePatch(patcher) {
+		options = append(options, UnifyByJSONMergePatch{})
+	}
+	return
+}
+
 type interceptor func(baseNode ast.Node, patchNode ast.Node) error
 
 func listMergeProcess(field *ast.Field, key string, baseList, patchList *ast.ListLit) {
@@ -185,19 +232,30 @@ func isStrategyRetainKeys(node *ast.Field) bool {
 	return false
 }
 
-// IsOpenPatch check if patcher has open annotation
-func IsOpenPatch(patcher cue.Value) bool {
+// IsJSONMergePatch check if patcher is json merge patch
+func IsJSONMergePatch(patcher cue.Value) bool {
 	tags := findCommentTag(patcher.Doc())
-	for tk, tv := range tags {
-		if tk == TagPatchStrategy && tv == StrategyOpen {
-			return true
-		}
-	}
-	return false
+	return tags[TagPatchStrategy] == StrategyJSONMergePatch
+}
+
+// IsJSONPatch check if patcher is json patch
+func IsJSONPatch(patcher cue.Value) bool {
+	tags := findCommentTag(patcher.Doc())
+	return tags[TagPatchStrategy] == StrategyJSONPatch
 }
 
 // StrategyUnify unify the objects by the strategy
-func StrategyUnify(base, patch string) (string, error) {
+func StrategyUnify(base, patch string, options ...UnifyOption) (ret string, err error) {
+	params := newUnifyParams(options...)
+	var patchOpts []interceptor
+	if params.PatchStrategy == StrategyJSONMergePatch || params.PatchStrategy == StrategyJSONPatch {
+		base, err = OpenBaiscLit(base)
+		if err != nil {
+			return base, err
+		}
+	} else {
+		patchOpts = []interceptor{strategyPatchHandle()}
+	}
 	baseFile, err := parser.ParseFile("-", base, parser.ParseComments)
 	if err != nil {
 		return "", errors.WithMessage(err, "invalid base cue file")
@@ -207,10 +265,10 @@ func StrategyUnify(base, patch string) (string, error) {
 		return "", errors.WithMessage(err, "invalid patch cue file")
 	}
 
-	return strategyUnify(baseFile, patchFile, strategyPatchHandle())
+	return strategyUnify(baseFile, patchFile, params, patchOpts...)
 }
 
-func strategyUnify(baseFile *ast.File, patchFile *ast.File, patchOpts ...interceptor) (string, error) {
+func strategyUnify(baseFile *ast.File, patchFile *ast.File, params *UnifyParams, patchOpts ...interceptor) (string, error) {
 	for _, option := range patchOpts {
 		if err := option(baseFile, patchFile); err != nil {
 			return "", errors.WithMessage(err, "process patchOption")
@@ -228,6 +286,12 @@ func strategyUnify(baseFile *ast.File, patchFile *ast.File, patchOpts ...interce
 		return "", errors.WithMessage(err, "compile patch file")
 	}
 
+	if params.PatchStrategy == StrategyJSONMergePatch {
+		return jsonMergePatch(baseInst.Value(), patchInst.Value())
+	} else if params.PatchStrategy == StrategyJSONPatch {
+		return jsonPatch(baseInst.Value(), patchInst.Lookup("operations"))
+	}
+
 	ret := baseInst.Value().Unify(patchInst.Value())
 
 	rv, err := toString(ret)
@@ -272,3 +336,40 @@ func findCommentTag(commentGroup []*ast.CommentGroup) map[string]string {
 	}
 	return kval
 }
+
+func jsonMergePatch(base cue.Value, patch cue.Value) (string, error) {
+	baseJSON, err := base.MarshalJSON()
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to marshal base value")
+	}
+	patchJSON, err := patch.MarshalJSON()
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to marshal patch value")
+	}
+	merged, err := jsonpatch.MergePatch(baseJSON, patchJSON)
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to merge base value and patch value by JsonMergePatch")
+	}
+	return string(merged), nil
+}
+
+func jsonPatch(base cue.Value, patch cue.Value) (string, error) {
+	baseJSON, err := base.MarshalJSON()
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to marshal base value")
+	}
+	patchJSON, err := patch.MarshalJSON()
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to marshal patch value")
+	}
+	decodedPatch, err := jsonpatch.DecodePatch(patchJSON)
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to decode patch")
+	}
+
+	merged, err := decodedPatch.Apply(baseJSON)
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to apply json patch")
+	}
+	return string(merged), nil
+}

test/e2e-test/trait_test.go

@@ -0,0 +1,107 @@
+/*
+Copyright 2021 The KubeVela 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 controllers_test
+
+import (
+	"context"
+	"io/ioutil"
+	"time"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	appsv1 "k8s.io/api/apps/v1"
+	corev1 "k8s.io/api/core/v1"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/utils/pointer"
+	"sigs.k8s.io/yaml"
+
+	"github.com/oam-dev/kubevela/apis/core.oam.dev/v1beta1"
+)
+
+func readAppFromFile(filename string) (*v1beta1.Application, error) {
+	bs, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	app := &v1beta1.Application{}
+	if err = yaml.Unmarshal(bs, app); err != nil {
+		return nil, err
+	}
+	return app, nil
+}
+
+var _ = Describe("Trait tests", func() {
+	ctx := context.Background()
+	var namespace string
+
+	BeforeEach(func() {
+		namespace = randomNamespaceName("trait-test")
+		Expect(k8sClient.Create(ctx, &corev1.Namespace{ObjectMeta: v1.ObjectMeta{Name: namespace}})).Should(Succeed())
+	})
+
+	AfterEach(func() {
+		ns := &corev1.Namespace{}
+		Expect(k8sClient.Get(ctx, types.NamespacedName{Name: namespace}, ns)).Should(Succeed())
+		Expect(k8sClient.Delete(ctx, ns)).Should(Succeed())
+	})
+
+	Context("Test app with traits", func() {
+		It("Test json-patch trait", func() {
+			app, err := readAppFromFile("../../docs/examples/traits/json-patch/example.yaml")
+			Expect(err).Should(Succeed())
+			app.SetNamespace(namespace)
+			Expect(k8sClient.Create(ctx, app)).Should(Succeed())
+			Eventually(func(g Gomega) {
+				deploy := &appsv1.Deployment{}
+				g.Expect(k8sClient.Get(ctx, types.NamespacedName{Namespace: namespace, Name: "busybox"}, deploy)).Should(Succeed())
+				g.Expect(deploy.Labels).ShouldNot(BeNil())
+				g.Expect(deploy.Labels["deploy-label-key"]).Should(Equal("deploy-label-added-value"))
+				g.Expect(deploy.Spec.Replicas).Should(Equal(pointer.Int32(3)))
+				g.Expect(deploy.Spec.Template.ObjectMeta.Labels).ShouldNot(BeNil())
+				g.Expect(deploy.Spec.Template.ObjectMeta.Labels["pod-label-key"]).Should(Equal("pod-label-modified-value"))
+				g.Expect(deploy.Spec.Template.ObjectMeta.Labels["to-delete-label-key"]).ShouldNot(Equal("to-delete-label-value"))
+				g.Expect(len(deploy.Spec.Template.Spec.Containers)).Should(Equal(2))
+				g.Expect(deploy.Spec.Template.Spec.Containers[1].Name).Should(Equal("busybox-sidecar"))
+				g.Expect(deploy.Spec.Template.Spec.Containers[1].Image).Should(Equal("busybox:1.34"))
+				g.Expect(deploy.Spec.Template.Spec.Containers[1].Command).Should(Equal([]string{"sleep", "864000"}))
+			}, 15*time.Second).Should(Succeed())
+		})
+
+		It("Test json-merge-patch trait", func() {
+			app, err := readAppFromFile("../../docs/examples/traits/json-merge-patch/example.yaml")
+			Expect(err).Should(Succeed())
+			app.SetNamespace(namespace)
+			Expect(k8sClient.Create(ctx, app)).Should(Succeed())
+			Eventually(func(g Gomega) {
+				deploy := &appsv1.Deployment{}
+				g.Expect(k8sClient.Get(ctx, types.NamespacedName{Namespace: namespace, Name: "busybox"}, deploy)).Should(Succeed())
+				g.Expect(deploy.Labels).ShouldNot(BeNil())
+				g.Expect(deploy.Labels["deploy-label-key"]).Should(Equal("deploy-label-added-value"))
+				g.Expect(deploy.Spec.Replicas).Should(Equal(pointer.Int32(3)))
+				g.Expect(deploy.Spec.Template.ObjectMeta.Labels).ShouldNot(BeNil())
+				g.Expect(deploy.Spec.Template.ObjectMeta.Labels["pod-label-key"]).Should(Equal("pod-label-modified-value"))
+				_, exists := deploy.Spec.Template.ObjectMeta.Labels["to-delete-label-key"]
+				g.Expect(exists).Should(BeFalse())
+				g.Expect(len(deploy.Spec.Template.Spec.Containers)).Should(Equal(1))
+				g.Expect(deploy.Spec.Template.Spec.Containers[0].Name).Should(Equal("busybox-new"))
+				g.Expect(deploy.Spec.Template.Spec.Containers[0].Image).Should(Equal("busybox:1.34"))
+				g.Expect(deploy.Spec.Template.Spec.Containers[0].Command).Should(Equal([]string{"sleep", "864000"}))
+			}, 15*time.Second).Should(Succeed())
+		})
+	})
+})

vela-templates/definitions/internal/trait/json-merge-patch.cue

@@ -1,8 +1,8 @@
-patch: {
+"json-merge-patch": {
 	type: "trait"
 	annotations: {}
 	labels: {}
-	description: "Patch the output directly."
+	description: "Patch the output following Json Merge Patch strategy, following RFC 7396."
 	attributes: {
 		podDisruptive: true
 		appliesToWorkloads: ["*"]
@@ -10,6 +10,6 @@ patch: {
 }
 template: {
 	parameter: {...}
-	// +patchStrategy=open
+	// +patchStrategy=jsonMergePatch
 	patch: parameter
 }

vela-templates/definitions/internal/trait/json-patch.cue

@@ -0,0 +1,15 @@
+"json-patch": {
+	type: "trait"
+	annotations: {}
+	labels: {}
+	description: "Patch the output following Json Patch strategy, following RFC 6902."
+	attributes: {
+		podDisruptive: true
+		appliesToWorkloads: ["*"]
+	}
+}
+template: {
+	parameter: operations: [...{...}]
+	// +patchStrategy=jsonPatch
+	patch: parameter
+}