add ability to change MergeOptions for Patch Strategic Merge

api/filters/patchstrategicmerge/patchstrategicmerge.go

@@ -4,26 +4,29 @@
 package patchstrategicmerge
 
 import (
+	"cmp"
 	"sigs.k8s.io/kustomize/kyaml/kio"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 	"sigs.k8s.io/kustomize/kyaml/yaml/merge2"
 )
 
 type Filter struct {
-	Patch *yaml.RNode
+	Patch        *yaml.RNode
+	MergeOptions *yaml.MergeOptions
 }
 
 var _ kio.Filter = Filter{}
 
 // Filter does a strategic merge patch, which can delete nodes.
 func (pf Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
 	var result []*yaml.RNode
+	mergeOptions := *cmp.Or(pf.MergeOptions, &yaml.MergeOptions{
+		ListIncreaseDirection: yaml.MergeOptionsListPrepend,
+	})
 	for i := range nodes {
 		r, err := merge2.Merge(
 			pf.Patch, nodes[i],
-			yaml.MergeOptions{
-				ListIncreaseDirection: yaml.MergeOptionsListPrepend,
-			},
+			mergeOptions,
 		)
 		if err != nil {
 			return nil, err

api/filters/patchstrategicmerge/patchstrategicmerge_test.go

@@ -921,3 +921,150 @@ data:
 		})
 	}
 }
+
+func TestFilterMergeOptionsListAppend(t *testing.T) {
+	testCases := map[string]struct {
+		input    string
+		patch    *yaml.RNode
+		expected string
+	}{
+		"container patch": {
+			input: `
+apiVersion: apps/v1
+metadata:
+  name: myDeploy
+kind: Deployment
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo1
+      - name: foo2
+      - name: foo3
+`,
+			patch: yaml.MustParse(`
+apiVersion: apps/v1
+metadata:
+  name: myDeploy
+kind: Deployment
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo0
+`),
+			expected: `
+apiVersion: apps/v1
+metadata:
+  name: myDeploy
+kind: Deployment
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo1
+      - name: foo2
+      - name: foo3
+      - name: foo0
+`,
+		},
+		"volumes patch": {
+			input: `
+apiVersion: apps/v1
+metadata:
+  name: myDeploy
+kind: Deployment
+spec:
+  template:
+    spec:
+      volumes:
+      - name: foo1
+      - name: foo2
+      - name: foo3
+`,
+			patch: yaml.MustParse(`
+apiVersion: apps/v1
+metadata:
+  name: myDeploy
+kind: Deployment
+spec:
+  template:
+    spec:
+      volumes:
+      - name: foo0
+`),
+			expected: `
+apiVersion: apps/v1
+metadata:
+  name: myDeploy
+kind: Deployment
+spec:
+  template:
+    spec:
+      volumes:
+      - name: foo1
+      - name: foo2
+      - name: foo3
+      - name: foo0
+`,
+		},
+		"merge list - directive": {
+			input: `
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: myDeploy
+spec:
+  template:
+    spec:
+      containers:
+      - name: test
+        image: test
+`,
+			patch: yaml.MustParse(`
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: myDeploy
+spec:
+  template:
+    spec:
+      containers:
+      - name: test2
+        image: test2
+      - $patch: merge   
+`),
+			expected: `
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: myDeploy
+spec:
+  template:
+    spec:
+      containers:
+      - name: test
+        image: test
+      - name: test2
+        image: test2
+`,
+		},
+	}
+
+	for tn, tc := range testCases {
+		t.Run(tn, func(t *testing.T) {
+			f := Filter{
+				Patch: tc.patch,
+				MergeOptions: &yaml.MergeOptions{
+					ListIncreaseDirection: yaml.MergeOptionsListAppend,
+				},
+			}
+			if !assert.Equal(t,
+				strings.TrimSpace(tc.expected),
+				strings.TrimSpace(
+					filtertest.RunFilter(t, tc.input, f))) {
+				t.FailNow()
+			}
+		})
+	}
+}

api/internal/target/kusttarget.go

@@ -24,6 +24,7 @@ import (
 	"sigs.k8s.io/kustomize/api/types"
 	"sigs.k8s.io/kustomize/kyaml/errors"
 	"sigs.k8s.io/kustomize/kyaml/openapi"
+	kyaml "sigs.k8s.io/kustomize/kyaml/yaml"
 	"sigs.k8s.io/yaml"
 )
 
@@ -36,19 +37,22 @@ type KustTarget struct {
 	rFactory      *resmap.Factory
 	pLdr          *loader.Loader
 	origin        *resource.Origin
+	mergeOptions  *kyaml.MergeOptions
 }
 
 // NewKustTarget returns a new instance of KustTarget.
 func NewKustTarget(
 	ldr ifc.Loader,
 	validator ifc.Validator,
 	rFactory *resmap.Factory,
-	pLdr *loader.Loader) *KustTarget {
+	pLdr *loader.Loader,
+	mOpts *kyaml.MergeOptions) *KustTarget {
 	return &KustTarget{
-		ldr:       ldr,
-		validator: validator,
-		rFactory:  rFactory,
-		pLdr:      pLdr.LoaderWithWorkingDir(ldr.Root()),
+		ldr:          ldr,
+		validator:    validator,
+		rFactory:     rFactory,
+		pLdr:         pLdr.LoaderWithWorkingDir(ldr.Root()),
+		mergeOptions: mOpts,
 	}
 }
 
@@ -488,7 +492,7 @@ func (kt *KustTarget) accumulateComponents(
 func (kt *KustTarget) accumulateDirectory(
 	ra *accumulator.ResAccumulator, ldr ifc.Loader, isComponent bool) (*accumulator.ResAccumulator, error) {
 	defer ldr.Cleanup()
-	subKt := NewKustTarget(ldr, kt.validator, kt.rFactory, kt.pLdr)
+	subKt := NewKustTarget(ldr, kt.validator, kt.rFactory, kt.pLdr, kt.mergeOptions)
 	err := subKt.Load()
 	if err != nil {
 		return nil, errors.WrapPrefixf(

api/internal/target/kusttarget_configplugin.go

@@ -232,9 +232,11 @@ var transformerConfigurators = map[builtinhelpers.BuiltinPluginType]func(
 			return
 		}
 		var c struct {
-			Paths []types.PatchStrategicMerge `json:"paths,omitempty" yaml:"paths,omitempty"`
+			Paths        []types.PatchStrategicMerge `json:"paths,omitempty" yaml:"paths,omitempty"`
+			MergeOptions *yaml.MergeOptions          `json:"mergeOptions,omitempty" yaml:"mergeOptions,omitempty"`
 		}
 		c.Paths = kt.kustomization.PatchesStrategicMerge
+		c.MergeOptions = kt.mergeOptions
 		p := f()
 		err = kt.configureBuiltinPlugin(p, c, bpt)
 		if err != nil {
@@ -250,16 +252,18 @@ var transformerConfigurators = map[builtinhelpers.BuiltinPluginType]func(
 			return
 		}
 		var c struct {
-			Path    string          `json:"path,omitempty" yaml:"path,omitempty"`
-			Patch   string          `json:"patch,omitempty" yaml:"patch,omitempty"`
-			Target  *types.Selector `json:"target,omitempty" yaml:"target,omitempty"`
-			Options map[string]bool `json:"options,omitempty" yaml:"options,omitempty"`
+			Path         string             `json:"path,omitempty" yaml:"path,omitempty"`
+			Patch        string             `json:"patch,omitempty" yaml:"patch,omitempty"`
+			Target       *types.Selector    `json:"target,omitempty" yaml:"target,omitempty"`
+			Options      map[string]bool    `json:"options,omitempty" yaml:"options,omitempty"`
+			MergeOptions *yaml.MergeOptions `json:"mergeOptions,omitempty" yaml:"mergeOptions,omitempty"`
 		}
 		for _, pc := range kt.kustomization.Patches {
 			c.Target = pc.Target
 			c.Patch = pc.Patch
 			c.Path = pc.Path
 			c.Options = pc.Options
+			c.MergeOptions = kt.mergeOptions
 			p := f()
 			err = kt.configureBuiltinPlugin(p, c, bpt)
 			if err != nil {

api/internal/target/maker_test.go

@@ -4,6 +4,7 @@
 package target_test
 
 import (
+	"sigs.k8s.io/kustomize/kyaml/yaml"
 	"testing"
 
 	"sigs.k8s.io/kustomize/api/ifc"
@@ -68,5 +69,8 @@ func makeKustTargetWithRfAndLoaderOverride(
 		ldr,
 		valtest_test.MakeFakeValidator(),
 		rf,
-		pLdr.NewLoader(pc, rf, fSys))
+		pLdr.NewLoader(pc, rf, fSys),
+		&yaml.MergeOptions{
+			ListIncreaseDirection: yaml.MergeOptionsListPrepend,
+		})
 }