Merge pull request #2245 from pwittrock/merge3

Use OpenAPI when 3-way merging resources
2026-05-18 07:35:16 +00:00 · 2020-03-03 12:51:46 -08:00
parent 2a8a17e3af 5d1a0346b5
commit caa8fdc3cd
24 changed files with 991 additions and 507 deletions
--- a/kyaml/fieldmeta/fieldmeta.go
+++ b/kyaml/fieldmeta/fieldmeta.go
@@ -5,6 +5,7 @@ package fieldmeta

 import (
 	"encoding/json"
+	"reflect"
 	"strconv"
 	"strings"

@@ -36,16 +37,29 @@ type PartialFieldSetter struct {
 	Value string `yaml:"value" json:"value"`
 }

+// IsEmpty returns true if the FieldMeta has any empty Schema
+func (fm *FieldMeta) IsEmpty() bool {
+	if fm == nil {
+		return true
+	}
+	return reflect.DeepEqual(fm.Schema, spec.Schema{})
+}
+
 // Read reads the FieldMeta from a node
 func (fm *FieldMeta) Read(n *yaml.RNode) error {
-	if n.YNode().LineComment != "" {
-		v := strings.TrimLeft(n.YNode().LineComment, "#")
+	// check for metadata on head and line comments
+	comments := []string{n.YNode().LineComment, n.YNode().HeadComment}
+	for _, c := range comments {
+		if c == "" {
+			continue
+		}
+		c := strings.TrimLeft(c, "#")
 		// if it doesn't Unmarshal that is fine, it means there is no metadata
 		// other comments are valid, they just don't parse

-		// TODO: consider most sophisticated parsing techniques similar to what is used
+		// TODO: consider more sophisticated parsing techniques similar to what is used
 		// for go struct tags.
-		if err := fm.Schema.UnmarshalJSON([]byte(v)); err != nil {
+		if err := fm.Schema.UnmarshalJSON([]byte(c)); err != nil {
 			// note: don't return an error if the comment isn't a fieldmeta struct
 			return nil
 		}
--- a/kyaml/openapi/openapi.go
+++ b/kyaml/openapi/openapi.go
@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
+	"reflect"
 	"sync"

 	"github.com/go-openapi/spec"
@@ -32,6 +33,14 @@ type ResourceSchema struct {
 	Schema *spec.Schema
 }

+// IsEmpty returns true if the ResourceSchema is empty
+func (rs *ResourceSchema) IsEmpty() bool {
+	if rs == nil || rs.Schema == nil {
+		return true
+	}
+	return reflect.DeepEqual(*rs.Schema, spec.Schema{})
+}
+
 // SchemaForResourceType returns the Schema for the given Resource
 // TODO(pwittrock): create a version of this function that will return a schema
 // which can be used for duck-typed Resources -- e.g. contains common fields such
@@ -193,15 +202,15 @@ func SuppressBuiltInSchemaUse() {
 }

 // Elements returns the Schema for the elements of an array.
-func (r *ResourceSchema) Elements() *ResourceSchema {
+func (rs *ResourceSchema) Elements() *ResourceSchema {
 	// load the schema from swagger.json
 	initSchema()

-	if len(r.Schema.Type) != 1 || r.Schema.Type[0] != "array" {
+	if len(rs.Schema.Type) != 1 || rs.Schema.Type[0] != "array" {
 		// either not an array, or array has multiple types
 		return nil
 	}
-	s := *r.Schema.Items.Schema
+	s := *rs.Schema.Items.Schema
 	for s.Ref.String() != "" {
 		sc, e := Resolve(&s.Ref)
 		if e != nil {
@@ -219,8 +228,8 @@ const Elements = "[]"
 // Field is called.
 // If any Field or Elements call returns nil, then Lookup returns
 // nil immediately.
-func (r *ResourceSchema) Lookup(path ...string) *ResourceSchema {
-	s := r
+func (rs *ResourceSchema) Lookup(path ...string) *ResourceSchema {
+	s := rs
 	for _, p := range path {
 		if s == nil {
 			break
@@ -235,19 +244,19 @@ func (r *ResourceSchema) Lookup(path ...string) *ResourceSchema {
 }

 // Field returns the Schema for a field.
-func (r *ResourceSchema) Field(field string) *ResourceSchema {
+func (rs *ResourceSchema) Field(field string) *ResourceSchema {
 	// load the schema from swagger.json
 	initSchema()

 	// locate the Schema
-	s, found := r.Schema.Properties[field]
+	s, found := rs.Schema.Properties[field]
 	switch {
 	case found:
 		// no-op, continue with s as the schema
-	case r.Schema.AdditionalProperties != nil && r.Schema.AdditionalProperties.Schema != nil:
+	case rs.Schema.AdditionalProperties != nil && rs.Schema.AdditionalProperties.Schema != nil:
 		// map field type -- use Schema of the value
 		// (the key doesn't matter, they all have the same value type)
-		s = *r.Schema.AdditionalProperties.Schema
+		s = *rs.Schema.AdditionalProperties.Schema
 	default:
 		// no Schema found from either swagger.json or line comments
 		return nil
@@ -267,14 +276,14 @@ func (r *ResourceSchema) Field(field string) *ResourceSchema {
 }

 // PatchStrategyAndKey returns the patch strategy and merge key extensions
-func (r *ResourceSchema) PatchStrategyAndKey() (string, string) {
-	ps, found := r.Schema.Extensions[kubernetesPatchStrategyExtensionKey]
+func (rs *ResourceSchema) PatchStrategyAndKey() (string, string) {
+	ps, found := rs.Schema.Extensions[kubernetesPatchStrategyExtensionKey]
 	if !found {
 		// merge key and patch strategy must appear together
 		return "", ""
 	}

-	mk, found := r.Schema.Extensions[kubernetesMergeKeyExtensionKey]
+	mk, found := rs.Schema.Extensions[kubernetesMergeKeyExtensionKey]
 	if !found {
 		// merge key and patch strategy must appear together
 		return "", ""
--- a/kyaml/yaml/merge2/element_test.go
+++ b/kyaml/yaml/merge2/element_test.go
@@ -4,21 +4,21 @@
 package merge2_test

 var elementTestCases = []testCase{
-	{`merge Element -- keep field in dest`,
-		`
+	{description: `merge Element -- keep field in dest`,
+		source: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v1
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v0
  command: ['run.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -27,21 +27,21 @@ items:
 `,
 	},

-	{`merge Element -- add field to dest`,
-		`
+	{description: `merge Element -- add field to dest`,
+		source: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v1
  command: ['run.sh']
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v0
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -50,19 +50,19 @@ items:
 `,
 	},

-	{`merge Element -- add list, empty in dest`,
-		`
+	{description: `merge Element -- add list, empty in dest`,
+		source: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v1
  command: ['run.sh']
 `,
-		`
+		dest: `
 kind: Deployment
 items: []
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -71,18 +71,18 @@ items:
 `,
 	},

-	{`merge Element -- add list, missing from dest`,
-		`
+	{description: `merge Element -- add list, missing from dest`,
+		source: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v1
  command: ['run.sh']
 `,
-		`
+		dest: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -91,8 +91,8 @@ items:
 `,
 	},

-	{`merge Element -- add Element first`,
-		`
+	{description: `merge Element -- add Element first`,
+		source: `
 kind: Deployment
 items:
 - name: bar
@@ -101,13 +101,13 @@ items:
 - name: foo
  image: foo:v1
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v0
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -118,8 +118,8 @@ items:
 `,
 	},

-	{`merge Element -- add Element second`,
-		`
+	{description: `merge Element -- add Element second`,
+		source: `
 kind: Deployment
 items:
 - name: foo
@@ -128,13 +128,13 @@ items:
  image: bar:v1
  command: ['run2.sh']
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v0
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -148,11 +148,11 @@ items:
 	//
 	// Test Case
 	//
-	{`keep list -- list missing from src`,
-		`
+	{description: `keep list -- list missing from src`,
+		source: `
 kind: Deployment
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
@@ -161,7 +161,7 @@ items:
  image: bar:v1
  command: ['run2.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -175,14 +175,14 @@ items:
 	//
 	// Test Case
 	//
-	{`keep Element -- element missing in src`,
-		`
+	{description: `keep Element -- element missing in src`,
+		source: `
 kind: Deployment
 items:
 - name: foo
  image: foo:v1
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
@@ -191,7 +191,7 @@ items:
  image: bar:v1
  command: ['run2.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -205,12 +205,12 @@ items:
 	//
 	// Test Case
 	//
-	{`keep element -- empty list in src`,
-		`
+	{description: `keep element -- empty list in src`,
+		source: `
 kind: Deployment
 items: {}
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
@@ -219,7 +219,7 @@ items:
  image: bar:v1
  command: ['run2.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - name: foo
@@ -233,12 +233,12 @@ items:
 	//
 	// Test Case
 	//
-	{`remove Element -- null in src`,
-		`
+	{description: `remove Element -- null in src`,
+		source: `
 kind: Deployment
 items: null
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - name: foo
@@ -247,8 +247,97 @@ items:
  image: bar:v1
  command: ['run2.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 `,
 	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys no merge'`,
+		source: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		dest: `
+kind: Deployment
+containers:
+- name: foo
+  image: foo:bar
+`,
+		expected: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using schema`,
+		source: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+        command: ['run2.sh']
+`,
+		dest: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+        image: foo:bar
+`,
+		expected: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+        image: foo:bar
+        command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using explicit schema as line comment'`,
+		source: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		dest: `
+kind: Deployment
+containers: # {"items":{"$ref": "#/definitions/io.k8s.api.core.v1.Container"},"type":"array","x-kubernetes-patch-merge-key":"name","x-kubernetes-patch-strategy": "merge"}
+- name: foo # hell ow
+  image: foo:bar
+`,
+		expected: `
+kind: Deployment
+containers: # {"items":{"$ref": "#/definitions/io.k8s.api.core.v1.Container"},"type":"array","x-kubernetes-patch-merge-key":"name","x-kubernetes-patch-strategy": "merge"}
+- name: foo
+  image: foo:bar
+  command: ['run2.sh']
+`,
+		noInfer: true,
+	},
 }
--- a/kyaml/yaml/merge2/list_test.go
+++ b/kyaml/yaml/merge2/list_test.go
@@ -4,21 +4,21 @@
 package merge2_test

 var listTestCases = []testCase{
-	{`replace List -- different value in dest`,
-		`
+	{description: `replace List -- different value in dest`,
+		source: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - 0
 - 1
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - 1
@@ -27,18 +27,18 @@ items:
 `,
 	},

-	{`replace List -- missing from dest`,
-		`
+	{description: `replace List -- missing from dest`,
+		source: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		dest: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - 1
@@ -50,22 +50,22 @@ items:
 	//
 	// Test Case
 	//
-	{`keep List -- same value in src and dest`,
-		`
+	{description: `keep List -- same value in src and dest`,
+		source: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - 1
@@ -77,18 +77,18 @@ items:
 	//
 	// Test Case
 	//
-	{`keep List -- unspecified in src`,
-		`
+	{description: `keep List -- unspecified in src`,
+		source: `
 kind: Deployment
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		expected: `
 kind: Deployment
 items:
 - 1
@@ -100,19 +100,19 @@ items:
 	//
 	// Test Case
 	//
-	{`remove List -- null in src`,
-		`
+	{description: `remove List -- null in src`,
+		source: `
 kind: Deployment
 items: null
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		expected: `
 kind: Deployment
 `,
 	},
@@ -120,19 +120,19 @@ kind: Deployment
 	//
 	// Test Case
 	//
-	{`remove list -- empty in src`,
-		`
+	{description: `remove list -- empty in src`,
+		source: `
 kind: Deployment
 items: {}
 `,
-		`
+		dest: `
 kind: Deployment
 items:
 - 1
 - 2
 - 3
 `,
-		`
+		expected: `
 kind: Deployment
 items: {}
 `,
--- a/kyaml/yaml/merge2/map_test.go
+++ b/kyaml/yaml/merge2/map_test.go
@@ -4,19 +4,19 @@
 package merge2_test

 var mapTestCases = []testCase{
-	{`merge Map -- update field in dest`,
-		`
+	{description: `merge Map -- update field in dest`,
+		source: `
 kind: Deployment
 spec:
  foo: bar1
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar0
  baz: buz
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -24,19 +24,19 @@ spec:
 `,
 	},

-	{`merge Map -- add field to dest`,
-		`
+	{description: `merge Map -- add field to dest`,
+		source: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar0
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -44,18 +44,18 @@ spec:
 `,
 	},

-	{`merge Map -- add list, empty in dest`,
-		`
+	{description: `merge Map -- add list, empty in dest`,
+		source: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		dest: `
 kind: Deployment
 spec: {}
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -63,17 +63,17 @@ spec:
 `,
 	},

-	{`merge Map -- add list, missing from dest`,
-		`
+	{description: `merge Map -- add list, missing from dest`,
+		source: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		dest: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -81,19 +81,19 @@ spec:
 `,
 	},

-	{`merge Map -- add Map first`,
-		`
+	{description: `merge Map -- add Map first`,
+		source: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar1
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -101,19 +101,19 @@ spec:
 `,
 	},

-	{`merge Map -- add Map second`,
-		`
+	{description: `merge Map -- add Map second`,
+		source: `
 kind: Deployment
 spec:
  baz: buz
  foo: bar1
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar1
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -124,17 +124,17 @@ spec:
 	//
 	// Test Case
 	//
-	{`keep map -- map missing from src`,
-		`
+	{description: `keep map -- map missing from src`,
+		source: `
 kind: Deployment
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -145,18 +145,18 @@ spec:
 	//
 	// Test Case
 	//
-	{`keep map -- empty list in src`,
-		`
+	{description: `keep map -- empty list in src`,
+		source: `
 kind: Deployment
 items: {}
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		expected: `
 kind: Deployment
 spec:
  foo: bar1
@@ -168,18 +168,18 @@ items: {}
 	//
 	// Test Case
 	//
-	{`remove Map -- null in src`,
-		`
+	{description: `remove Map -- null in src`,
+		source: `
 kind: Deployment
 spec: null
 `,
-		`
+		dest: `
 kind: Deployment
 spec:
  foo: bar1
  baz: buz
 `,
-		`
+		expected: `
 kind: Deployment
 `,
 	},
--- a/kyaml/yaml/merge2/merge2.go
+++ b/kyaml/yaml/merge2/merge2.go
@@ -6,6 +6,7 @@
 package merge2

 import (
+	"sigs.k8s.io/kustomize/kyaml/openapi"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 	"sigs.k8s.io/kustomize/kyaml/yaml/walk"
 )
@@ -16,7 +17,7 @@ func Merge(src, dest *yaml.RNode) (*yaml.RNode, error) {
 }

 // Merge parses the arguments, and merges fields from srcStr into destStr.
-func MergeStrings(srcStr, destStr string) (string, error) {
+func MergeStrings(srcStr, destStr string, infer bool) (string, error) {
 	src, err := yaml.Parse(srcStr)
 	if err != nil {
 		return "", err
@@ -26,10 +27,15 @@ func MergeStrings(srcStr, destStr string) (string, error) {
 		return "", err
 	}

-	result, err := Merge(src, dest)
+	result, err := walk.Walker{
+		Sources:               []*yaml.RNode{dest, src},
+		Visitor:               Merger{},
+		InferAssociativeLists: infer,
+	}.Walk()
 	if err != nil {
 		return "", err
 	}
+
 	return result.String()
 }

@@ -39,7 +45,7 @@ type Merger struct {

 var _ walk.Visitor = Merger{}

-func (m Merger) VisitMap(nodes walk.Sources) (*yaml.RNode, error) {
+func (m Merger) VisitMap(nodes walk.Sources, s *openapi.ResourceSchema) (*yaml.RNode, error) {
 	if err := m.SetComments(nodes); err != nil {
 		return nil, err
 	}
@@ -58,7 +64,7 @@ func (m Merger) VisitMap(nodes walk.Sources) (*yaml.RNode, error) {
 	return nodes.Dest(), nil
 }

-func (m Merger) VisitScalar(nodes walk.Sources) (*yaml.RNode, error) {
+func (m Merger) VisitScalar(nodes walk.Sources, s *openapi.ResourceSchema) (*yaml.RNode, error) {
 	if err := m.SetComments(nodes); err != nil {
 		return nil, err
 	}
@@ -73,7 +79,7 @@ func (m Merger) VisitScalar(nodes walk.Sources) (*yaml.RNode, error) {
 	return nodes.Dest(), nil
 }

-func (m Merger) VisitList(nodes walk.Sources, kind walk.ListKind) (*yaml.RNode, error) {
+func (m Merger) VisitList(nodes walk.Sources, s *openapi.ResourceSchema, kind walk.ListKind) (*yaml.RNode, error) {
 	if err := m.SetComments(nodes); err != nil {
 		return nil, err
 	}
--- a/kyaml/yaml/merge2/merge2_old_test.go
+++ b/kyaml/yaml/merge2/merge2_old_test.go
@@ -365,7 +365,7 @@ a:
  b:
    # header comment
    c: d
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
@@ -385,7 +385,7 @@ a:
  b:
    c: d
    # footer comment
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
@@ -404,7 +404,7 @@ a:
 a:
  b:
    c: d # line comment
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
@@ -426,7 +426,7 @@ a:
  b:
    # replace comment
    c: d
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
@@ -447,7 +447,7 @@ a:
  b:
    c: d
    # replace comment
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
@@ -466,7 +466,7 @@ a:
 a:
  b:
    c: d # replace comment
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
@@ -484,7 +484,7 @@ a:
 a:
  b:
    c: d # replace comment
-`)
+`, true)
 	if !assert.NoError(t, err) {
 		return
 	}
--- a/kyaml/yaml/merge2/merge2_test.go
+++ b/kyaml/yaml/merge2/merge2_test.go
@@ -17,24 +17,27 @@ var testCases = [][]testCase{scalarTestCases, listTestCases, elementTestCases, m

 func TestMerge(t *testing.T) {
 	for i := range testCases {
-		for _, tc := range testCases[i] {
-			actual, err := MergeStrings(tc.source, tc.dest)
-			if !assert.NoError(t, err, tc.description) {
-				t.FailNow()
-			}
-			e, err := filters.FormatInput(bytes.NewBufferString(tc.expected))
-			if !assert.NoError(t, err) {
-				t.FailNow()
-			}
-			estr := strings.TrimSpace(e.String())
-			a, err := filters.FormatInput(bytes.NewBufferString(actual))
-			if !assert.NoError(t, err) {
-				t.FailNow()
-			}
-			astr := strings.TrimSpace(a.String())
-			if !assert.Equal(t, estr, astr, tc.description) {
-				t.FailNow()
-			}
+		for j := range testCases[i] {
+			tc := testCases[i][j]
+			t.Run(tc.description, func(t *testing.T) {
+				actual, err := MergeStrings(tc.source, tc.dest, !tc.noInfer)
+				if !assert.NoError(t, err, tc.description) {
+					t.FailNow()
+				}
+				e, err := filters.FormatInput(bytes.NewBufferString(tc.expected))
+				if !assert.NoError(t, err) {
+					t.FailNow()
+				}
+				estr := strings.TrimSpace(e.String())
+				a, err := filters.FormatInput(bytes.NewBufferString(actual))
+				if !assert.NoError(t, err) {
+					t.FailNow()
+				}
+				astr := strings.TrimSpace(a.String())
+				if !assert.Equal(t, estr, astr, tc.description) {
+					t.FailNow()
+				}
+			})
 		}
 	}
 }
@@ -44,4 +47,5 @@ type testCase struct {
 	source      string
 	dest        string
 	expected    string
+	noInfer     bool
 }
--- a/kyaml/yaml/merge2/scalar_test.go
+++ b/kyaml/yaml/merge2/scalar_test.go
@@ -4,30 +4,30 @@
 package merge2_test

 var scalarTestCases = []testCase{
-	{`replace scalar -- different value in dest`,
-		`
+	{description: `replace scalar -- different value in dest`,
+		source: `
 kind: Deployment
 field: value1
 `,
-		`
+		dest: `
 kind: Deployment
 field: value0
 `,
-		`
+		expected: `
 kind: Deployment
 field: value1
 `,
 	},

-	{`replace scalar -- missing from dest`,
-		`
+	{description: `replace scalar -- missing from dest`,
+		source: `
 kind: Deployment
 field: value1
 `,
-		`
+		dest: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 field: value1
 `,
@@ -36,16 +36,16 @@ field: value1
 	//
 	// Test Case
 	//
-	{`keep scalar -- same value in src and dest`,
-		`
+	{description: `keep scalar -- same value in src and dest`,
+		source: `
 kind: Deployment
 field: value1
 `,
-		`
+		dest: `
 kind: Deployment
 field: value1
 `,
-		`
+		expected: `
 kind: Deployment
 field: value1
 `,
@@ -54,15 +54,15 @@ field: value1
 	//
 	// Test Case
 	//
-	{`keep scalar -- unspecified in src`,
-		`
+	{description: `keep scalar -- unspecified in src`,
+		source: `
 kind: Deployment
 `,
-		`
+		dest: `
 kind: Deployment
 field: value1
 `,
-		`
+		expected: `
 kind: Deployment
 field: value1
 `,
@@ -71,16 +71,16 @@ field: value1
 	//
 	// Test Case
 	//
-	{`remove scalar -- null in src`,
-		`
+	{description: `remove scalar -- null in src`,
+		source: `
 kind: Deployment
 field: null
 `,
-		`
+		dest: `
 kind: Deployment
 field: value1
 `,
-		`
+		expected: `
 kind: Deployment
 `,
 	},
@@ -88,16 +88,16 @@ kind: Deployment
 	//
 	// Test Case
 	//
-	{`remove scalar -- empty in src`,
-		`
+	{description: `remove scalar -- empty in src`,
+		source: `
 kind: Deployment
 field: {}
 `,
-		`
+		dest: `
 kind: Deployment
 field: value1
 `,
-		`
+		expected: `
 kind: Deployment
 field: {}
 `,
@@ -106,15 +106,15 @@ field: {}
 	//
 	// Test Case
 	//
-	{`remove scalar -- null in src, missing in dest`,
-		`
+	{description: `remove scalar -- null in src, missing in dest`,
+		source: `
 kind: Deployment
 field: null
 `,
-		`
+		dest: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 `,
 	},
@@ -122,15 +122,15 @@ kind: Deployment
 	//
 	// Test Case
 	//
-	{`merge an empty value`,
-		`
+	{description: `merge an empty value`,
+		source: `
 kind: Deployment
 field: {}
 `,
-		`
+		dest: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 field: {}
 `,
--- a/kyaml/yaml/merge3/element_test.go
+++ b/kyaml/yaml/merge3/element_test.go
@@ -7,14 +7,14 @@ var elementTestCases = []testCase{
 	//
 	// Test Case
 	//
-	{`Add an element to an existing list`,
-		`
+	{description: `Add an element to an existing list`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:1
 `,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
@@ -22,13 +22,13 @@ containers:
 - name: baz
  image: baz:2
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:1
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: foo
@@ -36,65 +36,65 @@ containers:
 - image: baz:2
  name: baz
  
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Add an element to a non-existing list`,
-		`
+	{description: `Add an element to a non-existing list`,
+		origin: `
 kind: Deployment`,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		local: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - image: foo:bar
  name: foo
-`, nil},
+`},

-	{`Add an element to a non-existing list, existing in dest`,
-		`
+	{description: `Add an element to a non-existing list, existing in dest`,
+		origin: `
 kind: Deployment`,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: baz
  image: baz:bar
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: baz
  image: baz:bar
 - image: foo:bar
  name: foo
-`, nil},
+`},

 	//
 	// Test Case
 	// TODO(pwittrock): Figure out if there is something better we can do here
 	// This element is missing from the destination -- only the new fields are added
-	{`Add a field to the element, element missing from dest`,
-		`
+	{description: `Add a field to the element, element missing from dest`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar`,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
@@ -102,22 +102,22 @@ containers:
  command:
  - run.sh
 `,
-		`
+		local: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - command:
  - run.sh
  name: foo
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Update a field on the elem, element missing from the dest`,
-		`
+	{description: `Update a field on the elem, element missing from the dest`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
@@ -125,7 +125,7 @@ containers:
  command:
  - run.sh
 `,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
@@ -133,210 +133,210 @@ containers:
  command: 
  - run2.sh
 `,
-		`
+		local: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - command:
  - run2.sh
  name: foo
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Update a field on the elem, element present in the dest`,
-		`
+	{description: `Update a field on the elem, element present in the dest`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
 `,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run2.sh']
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run2.sh']
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Add a field on the elem, element present in the dest`,
-		`
+	{description: `Add a field on the elem, element present in the dest`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run2.sh']
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run2.sh']
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Add a field on the elem, element and field present in the dest`,
-		`
+	{description: `Add a field on the elem, element and field present in the dest`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run2.sh']
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run2.sh']
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Ignore an element`,
-		`
+	{description: `Ignore an element`,
+		origin: `
 kind: Deployment
 containers: {}
 `,
-		`
+		update: `
 kind: Deployment
 containers: {}
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Leave deleted`,
-		`
+	{description: `Leave deleted`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 `,
-		`
+		local: `
 kind: Deployment
 `,
-		`
+		expected: `
 kind: Deployment
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Remove an element -- matching`,
-		`
+	{description: `Remove an element -- matching`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		expected: `
 kind: Deployment
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Remove an element -- field missing from update`,
-		`
+	{description: `Remove an element -- field missing from update`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
 `,
-		`
+		expected: `
 kind: Deployment
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Remove an element -- element missing`,
-		`
+	{description: `Remove an element -- element missing`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
@@ -344,13 +344,13 @@ containers:
 - name: baz
  image: baz:bar
 `,
-		`
+		update: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
@@ -359,60 +359,273 @@ containers:
 - name: baz
  image: baz:bar
 `,
-		`
+		expected: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Remove an element -- empty containers`,
-		`
+	{description: `Remove an element -- empty containers`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 containers: {}
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
 `,
-		`
+		expected: `
 kind: Deployment
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Remove an element -- missing list field`,
-		`
+	{description: `Remove an element -- missing list field`,
+		origin: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
 `,
-		`
+		update: `
 kind: Deployment
 `,
-		`
+		local: `
 kind: Deployment
 containers:
 - name: foo
  image: foo:bar
  command: ['run.sh']
 `,
-		`
+		expected: `
 kind: Deployment
-`, nil},
+`},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys no merge'`,
+		origin: `
+kind: Deployment
+containers:
+- name: foo
+`,
+		update: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		local: `
+kind: Deployment
+containers:
+- name: foo
+  image: foo:bar
+`,
+		expected: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using schema`,
+		origin: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+`,
+		update: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+        command: ['run2.sh']
+`,
+		local: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+        image: foo:bar
+`,
+		expected: `
+kind: Deployment
+apiVersion: apps/v1
+spec:
+  template:
+    spec:
+      containers:
+      - name: foo
+        image: foo:bar
+        command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using explicit schema as line comment'`,
+		origin: `
+kind: Deployment
+containers:
+- name: foo
+`,
+		update: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		local: `
+kind: Deployment
+containers: # {"items":{"$ref": "#/definitions/io.k8s.api.core.v1.Container"},"type":"array","x-kubernetes-patch-merge-key":"name","x-kubernetes-patch-strategy": "merge"}
+- name: foo # hell ow
+  image: foo:bar
+`,
+		expected: `
+kind: Deployment
+containers: # {"items":{"$ref": "#/definitions/io.k8s.api.core.v1.Container"},"type":"array","x-kubernetes-patch-merge-key":"name","x-kubernetes-patch-strategy": "merge"}
+- name: foo # hell ow
+  image: foo:bar
+  command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using explicit schema as head comment'`,
+		origin: `
+kind: Deployment
+containers:
+- name: foo
+`,
+		update: `
+kind: Deployment
+containers:
+- name: foo
+  command: ['run2.sh']
+`,
+		local: `
+kind: Deployment
+# {"items":{"$ref": "#/definitions/io.k8s.api.core.v1.Container"},"type":"array","x-kubernetes-patch-merge-key":"name","x-kubernetes-patch-strategy": "merge"}
+containers:
+- name: foo # hell ow
+  image: foo:bar
+`,
+		expected: `
+kind: Deployment
+# {"items":{"$ref": "#/definitions/io.k8s.api.core.v1.Container"},"type":"array","x-kubernetes-patch-merge-key":"name","x-kubernetes-patch-strategy": "merge"}
+containers:
+- name: foo # hell ow
+  image: foo:bar
+  command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using explicit schema to parent field'`,
+		origin: `
+kind: Deployment
+spec:
+  containers:
+  - name: foo
+`,
+		update: `
+kind: Deployment
+spec:
+  containers:
+  - name: foo
+    command: ['run2.sh']
+`,
+		local: `
+kind: Deployment
+spec: # {"$ref":"#/definitions/io.k8s.api.core.v1.PodSpec"}
+  containers:
+  - name: foo # hell ow
+    image: foo:bar
+`,
+		expected: `
+kind: Deployment
+spec: # {"$ref":"#/definitions/io.k8s.api.core.v1.PodSpec"}
+  containers:
+  - name: foo # hell ow
+    image: foo:bar
+    command: ['run2.sh']
+`,
+		noInfer: true,
+	},
+
+	//
+	// Test Case
+	//
+	{description: `no infer merge keys merge using explicit schema to parent field header'`,
+		origin: `
+kind: Deployment
+spec:
+  containers:
+  - name: foo
+`,
+		update: `
+kind: Deployment
+spec:
+  containers:
+  - name: foo
+    command: ['run2.sh']
+`,
+		local: `
+kind: Deployment
+# {"$ref":"#/definitions/io.k8s.api.core.v1.PodSpec"}
+spec:
+  containers:
+  - name: foo # hell ow
+    image: foo:bar
+`,
+		expected: `
+kind: Deployment
+# {"$ref":"#/definitions/io.k8s.api.core.v1.PodSpec"}
+spec:
+  containers:
+  - name: foo # hell ow
+    image: foo:bar
+    command: ['run2.sh']
+`,
+		noInfer: true,
+	},
 }
--- a/kyaml/yaml/merge3/list_test.go
+++ b/kyaml/yaml/merge3/list_test.go
@@ -9,224 +9,226 @@ var listTestCases = []testCase{
 	//
 	// Test Case
 	//
-	{`Replace list`,
-		`
+	{description: `Replace list`,
+		origin: `
 list:
 - 1
 - 2
 - 3`,
-		`
+		update: `
 list:
 - 2
 - 3
 - 4`,
-		`
+		local: `
 list:
 - 1
 - 2
 - 3`,
-		`
+		expected: `
 list:
 - 2
 - 3
- 4`, nil},
+- 4`},

 	//
 	// Test Case
 	//
-	{`Add an updated list`,
-		`
+	{description: `Add an updated list`,
+		origin: `
 apiVersion: apps/v1
 list: # old value
 - 1
 - 2
 - 3
 `,
-		`
+		update: `
 apiVersion: apps/v1
 list: # new value
 - 2
 - 3
 - 4
 `,
-		`
+		local: `
 apiVersion: apps/v1`,
-		`
+		expected: `
 apiVersion: apps/v1
 list:
 - 2
 - 3
 - 4
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Add keep an omitted field`,
-		`
+	{description: `Add keep an omitted field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: StatefulSet`,
-		`
+		local: `
 apiVersion: apps/v1
 list: # not present in sources
 - 2
 - 3
 - 4
 `,
-		`
+		expected: `
 apiVersion: apps/v1
 list: # not present in sources
 - 2
 - 3
 - 4
 kind: StatefulSet
-`, nil},
+`},

 	//
 	// Test Case
 	//
 	// TODO(#36): consider making this an error
-	{`Change an updated field`,
-		`
+	{description: `Change an updated field`,
+		origin: `
 apiVersion: apps/v1
 list: # old value
 - 1
 - 2
 - 3`,
-		`
+		update: `
 apiVersion: apps/v1
 list: # new value
 - 2
 - 3
 - 4`,
-		`
+		local: `
 apiVersion: apps/v1
 list: # conflicting value
 - a
 - b
 - c`,
-		`
+		expected: `
 apiVersion: apps/v1
 list: # conflicting value
 - 2
 - 3
 - 4
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Ignore a field -- set`,
-		`
+	{description: `Ignore a field -- set`,
+		origin: `
 apiVersion: apps/v1
 list: # ignore value
 - 1
 - 2
 - 3
 `,
-		`
+		update: `
 apiVersion: apps/v1
 list: # ignore value
 - 1
 - 2
- 3`, `
+- 3`,
+		local: `
 apiVersion: apps/v1
 list:
 - 2
 - 3
 - 4
-`, `
+`,
+		expected: `
 apiVersion: apps/v1
 list:
 - 2
 - 3
 - 4
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Ignore a field -- empty`,
-		`
+	{description: `Ignore a field -- empty`,
+		origin: `
 apiVersion: apps/v1
 list: # ignore value
 - 1
 - 2
 - 3`,
-		`
+		update: `
 apiVersion: apps/v1
 list: # ignore value
 - 1
 - 2
 - 3`,
-		`
+		local: `
 apiVersion: apps/v1
 `,
-		`
+		expected: `
 apiVersion: apps/v1
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Explicitly clear a field`,
-		`
+	{description: `Explicitly clear a field`,
+		origin: `
 apiVersion: apps/v1`,
-		`
+		update: `
 apiVersion: apps/v1
 list: null # clear`,
-		`
+		local: `
 apiVersion: apps/v1
 list: # value to clear
 - 1
 - 2
 - 3`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},

 	//
 	// Test Case
 	//
-	{`Implicitly clear a field`,
-		`
+	{description: `Implicitly clear a field`,
+		origin: `
 apiVersion: apps/v1
 list: # clear value
 - 1
 - 2
 - 3`,
-		`
+		update: `
 apiVersion: apps/v1`,
-		`
+		local: `
 apiVersion: apps/v1
 list: # old value
 - 1
 - 2
 - 3`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},

 	//
 	// Test Case
 	//
 	// TODO(#36): consider making this an error
-	{`Implicitly clear a changed field`,
-		`
+	{description: `Implicitly clear a changed field`,
+		origin: `
 apiVersion: apps/v1
 list: # old value
 - 1
 - 2
 - 3`,
-		`
+		update: `
 apiVersion: apps/v1`,
-		`
+		local: `
 apiVersion: apps/v1
 list: # old value
 - a
 - b
 - c`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},
 }
--- a/kyaml/yaml/merge3/map_test.go
+++ b/kyaml/yaml/merge3/map_test.go
@@ -7,267 +7,267 @@ var mapTestCases = []testCase{
 	//
 	// Test Case
 	//
-	{`Add the annotations map field`,
-		`
+	{description: `Add the annotations map field`,
+		origin: `
 kind: Deployment`,
-		`
+		update: `
 kind: Deployment
 metadata:
  annotations:
    d: e # add these annotations
 `,
-		`
+		local: `
 kind: Deployment`,
-		`
+		expected: `
 kind: Deployment
 metadata:
  annotations:
-    d: e # add these annotations`, nil},
+    d: e # add these annotations`},

 	//
 	// Test Case
 	//
-	{`Add an annotation to the field`,
-		`
+	{description: `Add an annotation to the field`,
+		origin: `
 kind: Deployment
 metadata:
  annotations:
    a: b`,
-		`
+		update: `
 kind: Deployment
 metadata:
  annotations:
    a: b
    d: e  # add these annotations`,
-		`
+		local: `
 kind: Deployment
 metadata:
  annotations:
    g: h  # keep these annotations`,
-		`
+		expected: `
 kind: Deployment
 metadata:
  annotations:
    g: h # keep these annotations
-    d: e # add these annotations`, nil},
+    d: e # add these annotations`},

 	//
 	// Test Case
 	//
-	{`Add an annotation to the field, field missing from dest`,
-		`
+	{description: `Add an annotation to the field, field missing from dest`,
+		origin: `
 kind: Deployment
 metadata:
  annotations:
    a: b # ignored because unchanged`,
-		`
+		update: `
 kind: Deployment
 metadata:
  annotations:
    a: b # ignore because unchanged
    d: e`,
-		`
+		local: `
 kind: Deployment`,
-		`
+		expected: `
 kind: Deployment
 metadata:
  annotations:
-    d: e`, nil},
+    d: e`},

 	//
 	// Test Case
 	//
-	{`Update an annotation on the field, field messing rom the dest`,
-		`
+	{description: `Update an annotation on the field, field messing rom the dest`,
+		origin: `
 kind: Deployment
 metadata:
  annotations:
    a: b
    d: c`,
-		`
+		update: `
 kind: Deployment
 metadata:
  annotations:
    a: b
    d: e  # set these annotations`,
-		`
+		local: `
 kind: Deployment
 metadata:
  annotations:
    g: h  # keep these annotations`,
-		`
+		expected: `
 kind: Deployment
 metadata:
  annotations:
    g: h # keep these annotations
-    d: e # set these annotations`, nil},
+    d: e # set these annotations`},

 	//
 	// Test Case
 	//
-	{`Add an annotation to the field, field missing from dest`,
-		`
+	{description: `Add an annotation to the field, field missing from dest`,
+		origin: `
 kind: Deployment
 metadata:
  annotations:
    a: b # ignored because unchanged`,
-		`
+		update: `
 kind: Deployment
 metadata:
  annotations:
    a: b # ignore because unchanged
    d: e`,
-		`
+		local: `
 kind: Deployment`,
-		`
+		expected: `
 kind: Deployment
 metadata:
  annotations:
-    d: e`, nil},
+    d: e`},

 	//
 	// Test Case
 	//
-	{`Remove an annotation`,
-		`
+	{description: `Remove an annotation`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
    a: b`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations: {}`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
    c: d
    a: b`,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
-    c: d`, nil},
+    c: d`},

 	//
 	// Test Case
 	//
 	// TODO(#36) support ~annotations~: {} deletion
-	{`Specify a field as empty that isn't present in the source`,
-		`
+	{description: `Specify a field as empty that isn't present in the source`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
  annotations: null`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
  annotations:
    a: b`,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
-  name: foo`, nil},
+  name: foo`},

 	//
 	// Test Case
 	//
-	{`Remove an annotation`,
-		`
+	{description: `Remove an annotation`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
    a: b`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
    c: d
    a: b`,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
-    c: d`, nil},
+    c: d`},

 	//
 	// Test Case
 	//
-	{`Remove annotations field`,
-		`
+	{description: `Remove annotations field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
    a: b`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo`,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
-`, nil},
+`},

 	//
 	// Test Case
 	//
-	{`Remove annotations field, but keep in dest`,
-		`
+	{description: `Remove annotations field, but keep in dest`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  annotations:
    a: b`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
  annotations:
    foo: bar # keep this annotation even though the parent field was removed`,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
  annotations:
-    foo: bar # keep this annotation even though the parent field was removed`, nil},
+    foo: bar # keep this annotation even though the parent field was removed`},

 	//
 	// Test Case
 	//
-	{`Remove annotations, but they are already empty`,
-		`
+	{description: `Remove annotations, but they are already empty`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
@@ -275,24 +275,24 @@ metadata:
  annotations:
    a: b
 `,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
 `,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
  annotations: {}
 `,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: Deployment
 metadata:
  name: foo
  annotations: {}
-`, nil},
+`},
 }
--- a/kyaml/yaml/merge3/merge3.go
+++ b/kyaml/yaml/merge3/merge3.go
@@ -13,11 +13,12 @@ import (
 func Merge(dest, original, update *yaml.RNode) (*yaml.RNode, error) {
 	// if update == nil && original != nil => declarative deletion

-	return walk.Walker{Visitor: Visitor{},
+	return walk.Walker{
+		Visitor: Visitor{},
 		Sources: []*yaml.RNode{dest, original, update}}.Walk()
 }

-func MergeStrings(dest, original, update string) (string, error) {
+func MergeStrings(dest, original, update string, infer bool) (string, error) {
 	srcOriginal, err := yaml.Parse(original)
 	if err != nil {
 		return "", err
@@ -31,7 +32,10 @@ func MergeStrings(dest, original, update string) (string, error) {
 		return "", err
 	}

-	result, err := Merge(d, srcOriginal, srcUpdated)
+	result, err := walk.Walker{
+		InferAssociativeLists: infer,
+		Visitor:               Visitor{},
+		Sources:               []*yaml.RNode{d, srcOriginal, srcUpdated}}.Walk()
 	if err != nil {
 		return "", err
 	}
--- a/kyaml/yaml/merge3/merge3_test.go
+++ b/kyaml/yaml/merge3/merge3_test.go
@@ -15,24 +15,27 @@ var testCases = [][]testCase{scalarTestCases, listTestCases, mapTestCases, eleme

 func TestMerge(t *testing.T) {
 	for i := range testCases {
-		for _, tc := range testCases[i] {
-			actual, err := MergeStrings(tc.local, tc.origin, tc.update)
-			if tc.err == nil {
-				if !assert.NoError(t, err, tc.description) {
-					t.FailNow()
+		for j := range testCases[i] {
+			tc := testCases[i][j]
+			t.Run(tc.description, func(t *testing.T) {
+				actual, err := MergeStrings(tc.local, tc.origin, tc.update, !tc.noInfer)
+				if tc.err == nil {
+					if !assert.NoError(t, err, tc.description) {
+						t.FailNow()
+					}
+					if !assert.Equal(t,
+						strings.TrimSpace(tc.expected), strings.TrimSpace(actual), tc.description) {
+						t.FailNow()
+					}
+				} else {
+					if !assert.Errorf(t, err, tc.description) {
+						t.FailNow()
+					}
+					if !assert.Contains(t, tc.err.Error(), err.Error()) {
+						t.FailNow()
+					}
 				}
-				if !assert.Equal(t,
-					strings.TrimSpace(tc.expected), strings.TrimSpace(actual), tc.description) {
-					t.FailNow()
-				}
-			} else {
-				if !assert.Errorf(t, err, tc.description) {
-					t.FailNow()
-				}
-				if !assert.Contains(t, tc.err.Error(), err.Error()) {
-					t.FailNow()
-				}
-			}
+			})
 		}
 	}
 }
@@ -44,4 +47,5 @@ type testCase struct {
 	local       string
 	expected    string
 	err         error
+	noInfer     bool
 }
--- a/kyaml/yaml/merge3/scalar_test.go
+++ b/kyaml/yaml/merge3/scalar_test.go
@@ -8,128 +8,128 @@ var scalarTestCases = []testCase{
 	//
 	// Test Case
 	//
-	{`Set and updated a field`,
-		`kind: Deployment`,
-		`kind: StatefulSet`,
-		`kind: Deployment`,
-		`kind: StatefulSet`, nil},
+	{description: `Set and updated a field`,
+		origin:   `kind: Deployment`,
+		update:   `kind: StatefulSet`,
+		local:    `kind: Deployment`,
+		expected: `kind: StatefulSet`},

-	{`Add an updated field`,
-		`
+	{description: `Add an updated field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment # old value`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: StatefulSet # new value`,
-		`
+		local: `
 apiVersion: apps/v1`,
-		`
+		expected: `
 apiVersion: apps/v1
-kind: StatefulSet # new value`, nil},
+kind: StatefulSet # new value`},

-	{`Add keep an omitted field`,
-		`
+	{description: `Add keep an omitted field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: StatefulSet`,
-		`
+		local: `
 apiVersion: apps/v1
 spec: foo # field not present in source
 `,
-		`
+		expected: `
 apiVersion: apps/v1
 spec: foo # field not present in source
 kind: StatefulSet
-`, nil},
+`},

 	//
 	// Test Case
 	//
 	// TODO(#36): consider making this an error
-	{`Change an updated field`,
-		`
+	{description: `Change an updated field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment # old value`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: StatefulSet # new value`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Service # conflicting value`,
-		`
+		expected: `
 apiVersion: apps/v1
-kind: StatefulSet # new value`, nil},
+kind: StatefulSet # new value`},

-	{`Ignore a field`,
-		`
+	{description: `Ignore a field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment # ignore this field`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: Deployment # ignore this field`,
-		`
+		local: `
 apiVersion: apps/v1`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},

-	{`Explicitly clear a field`,
-		`
+	{description: `Explicitly clear a field`,
+		origin: `
 apiVersion: apps/v1`,
-		`
+		update: `
 apiVersion: apps/v1
 kind: null # clear this value`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment # value to be cleared`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},

-	{`Implicitly clear a field`,
-		`
+	{description: `Implicitly clear a field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment # clear this field`,
-		`
+		update: `
 apiVersion: apps/v1`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: Deployment # clear this field`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},

 	//
 	// Test Case
 	//
 	// TODO(#36): consider making this an error
-	{`Implicitly clear a changed field`,
-		`
+	{description: `Implicitly clear a changed field`,
+		origin: `
 apiVersion: apps/v1
 kind: Deployment`,
-		`
+		update: `
 apiVersion: apps/v1`,
-		`
+		local: `
 apiVersion: apps/v1
 kind: StatefulSet`,
-		`
-apiVersion: apps/v1`, nil},
+		expected: `
+apiVersion: apps/v1`},

 	//
 	// Test Case
 	//
-	{`Merge an empty scalar value`,
-		`
+	{description: `Merge an empty scalar value`,
+		origin: `
 apiVersion: apps/v1
 `,
-		`
+		update: `
 apiVersion: apps/v1
 kind: {}
 `,
-		`
+		local: `
 apiVersion: apps/v1
 `,
-		`
+		expected: `
 apiVersion: apps/v1
 kind: {}
-`, nil},
+`},
 }
--- a/kyaml/yaml/merge3/visitor.go
+++ b/kyaml/yaml/merge3/visitor.go
@@ -4,6 +4,7 @@
 package merge3

 import (
+	"sigs.k8s.io/kustomize/kyaml/openapi"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 	"sigs.k8s.io/kustomize/kyaml/yaml/walk"
 )
@@ -17,7 +18,7 @@ const (

 type Visitor struct{}

-func (m Visitor) VisitMap(nodes walk.Sources) (*yaml.RNode, error) {
+func (m Visitor) VisitMap(nodes walk.Sources, s *openapi.ResourceSchema) (*yaml.RNode, error) {
 	if yaml.IsNull(nodes.Updated()) || yaml.IsNull(nodes.Dest()) {
 		// explicitly cleared from either dest or update
 		return walk.ClearNode, nil
@@ -36,7 +37,7 @@ func (m Visitor) VisitMap(nodes walk.Sources) (*yaml.RNode, error) {
 	return nodes.Dest(), nil
 }

-func (m Visitor) visitAList(nodes walk.Sources) (*yaml.RNode, error) {
+func (m Visitor) visitAList(nodes walk.Sources, _ *openapi.ResourceSchema) (*yaml.RNode, error) {
 	if yaml.IsEmpty(nodes.Updated()) && !yaml.IsEmpty(nodes.Origin()) {
 		// implicitly cleared from update -- element was deleted
 		return walk.ClearNode, nil
@@ -51,7 +52,7 @@ func (m Visitor) visitAList(nodes walk.Sources) (*yaml.RNode, error) {
 	return nodes.Dest(), nil
 }

-func (m Visitor) VisitScalar(nodes walk.Sources) (*yaml.RNode, error) {
+func (m Visitor) VisitScalar(nodes walk.Sources, s *openapi.ResourceSchema) (*yaml.RNode, error) {
 	if yaml.IsNull(nodes.Updated()) || yaml.IsNull(nodes.Dest()) {
 		// explicitly cleared from either dest or update
 		return nil, nil
@@ -103,9 +104,9 @@ func (m Visitor) visitNAList(nodes walk.Sources) (*yaml.RNode, error) {
 	return nodes.Dest(), nil
 }

-func (m Visitor) VisitList(nodes walk.Sources, kind walk.ListKind) (*yaml.RNode, error) {
+func (m Visitor) VisitList(nodes walk.Sources, s *openapi.ResourceSchema, kind walk.ListKind) (*yaml.RNode, error) {
 	if kind == walk.AssociativeList {
-		return m.visitAList(nodes)
+		return m.visitAList(nodes, s)
 	}
 	// non-associative list
 	return m.visitNAList(nodes)
--- a/kyaml/yaml/schema/schema.go
+++ b/kyaml/yaml/schema/schema.go
@@ -0,0 +1,34 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package schema contains libraries for working with the yaml and openapi packages.
+package schema
+
+import (
+	"sigs.k8s.io/kustomize/kyaml/openapi"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+// IsAssociative returns true if all elements in the list contain an AssociativeSequenceKey
+// as a field.
+func IsAssociative(schema *openapi.ResourceSchema, nodes []*yaml.RNode, infer bool) bool {
+	if schema != nil {
+		// use the schema to identify if the list is associative
+		s, _ := schema.PatchStrategyAndKey()
+		return s == "merge"
+	}
+	if !infer {
+		return false
+	}
+
+	for i := range nodes {
+		node := nodes[i]
+		if yaml.IsEmpty(node) {
+			continue
+		}
+		if node.IsAssociative() {
+			return true
+		}
+	}
+	return false
+}
--- a/kyaml/yaml/types.go
+++ b/kyaml/yaml/types.go
@@ -651,24 +651,8 @@ func (rn *RNode) VisitElements(fn func(node *RNode) error) error {
 // The order sets the precedence of the merge keys -- if multiple keys are present
 // in Resources in a list, then the FIRST key which ALL elements in the list have is used as the
 // associative key for merging that list.
-var AssociativeSequenceKeys = []string{
-	"mountPath", "devicePath", "ip", "type", "topologyKey", "name", "containerPort",
-}
-
-// IsAssociative returns true if all elements in the list contain an AssociativeSequenceKey
-// as a field.
-func IsAssociative(nodes []*RNode) bool {
-	for i := range nodes {
-		node := nodes[i]
-		if IsEmpty(node) {
-			continue
-		}
-		if node.IsAssociative() {
-			return true
-		}
-	}
-	return false
-}
+// Only infer name as a merge key.
+var AssociativeSequenceKeys = []string{"name"}

 // IsAssociative returns true if the RNode contains an AssociativeSequenceKey as a field.
 func (rn *RNode) IsAssociative() bool {
--- a/kyaml/yaml/walk/associative_sequence.go
+++ b/kyaml/yaml/walk/associative_sequence.go
@@ -7,28 +7,44 @@ import (
 	"strings"

 	"github.com/go-errors/errors"
+	"sigs.k8s.io/kustomize/kyaml/openapi"
 	"sigs.k8s.io/kustomize/kyaml/sets"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 )

 func (l *Walker) walkAssociativeSequence() (*yaml.RNode, error) {
 	// may require initializing the dest node
-	dest, err := l.Sources.setDestNode(l.VisitList(l.Sources, AssociativeList))
+	dest, err := l.Sources.setDestNode(l.VisitList(l.Sources, l.Schema, AssociativeList))
 	if dest == nil || err != nil {
 		return nil, err
 	}

-	// find the list of elements we need to recursively walk
-	key, err := l.elementKey()
-	if err != nil {
-		return nil, err
+	var key string
+	if l.Schema != nil {
+		_, key = l.Schema.PatchStrategyAndKey()
 	}
+	if key == "" { // no key from the schema, try to infer one
+		// find the list of elements we need to recursively walk
+		key, err = l.elementKey()
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	values := l.elementValues(key)

 	// recursively set the elements in the list
+	var s *openapi.ResourceSchema
+	if l.Schema != nil {
+		s = l.Schema.Elements()
+	}
 	for _, value := range values {
-		val, err := Walker{Visitor: l,
-			Sources: l.elementValue(key, value)}.Walk()
+		val, err := Walker{
+			InferAssociativeLists: l.InferAssociativeLists,
+			Visitor:               l,
+			Schema:                s,
+			Sources:               l.elementValue(key, value),
+		}.Walk()
 		if err != nil {
 			return nil, err
 		}
--- a/kyaml/yaml/walk/map.go
+++ b/kyaml/yaml/walk/map.go
@@ -6,6 +6,8 @@ package walk
 import (
 	"sort"

+	"sigs.k8s.io/kustomize/kyaml/fieldmeta"
+	"sigs.k8s.io/kustomize/kyaml/openapi"
 	"sigs.k8s.io/kustomize/kyaml/sets"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 )
@@ -18,15 +20,27 @@ import (
 // - set each source field value on l.Dest
 func (l Walker) walkMap() (*yaml.RNode, error) {
 	// get the new map value
-	dest, err := l.Sources.setDestNode(l.VisitMap(l.Sources))
+	dest, err := l.Sources.setDestNode(l.VisitMap(l.Sources, l.Schema))
 	if dest == nil || err != nil {
 		return nil, err
 	}

 	// recursively set the field values on the map
 	for _, key := range l.fieldNames() {
-		val, err := Walker{Visitor: l,
-			Sources: l.fieldValue(key), Path: append(l.Path, key)}.Walk()
+		var s *openapi.ResourceSchema
+		if l.Schema != nil {
+			s = l.Schema.Field(key)
+		}
+		fv, commentSch := l.fieldValue(key)
+		if commentSch != nil {
+			s = commentSch
+		}
+		val, err := Walker{
+			InferAssociativeLists: l.InferAssociativeLists,
+			Visitor:               l,
+			Schema:                s,
+			Sources:               fv,
+			Path:                  append(l.Path, key)}.Walk()
 		if err != nil {
 			return nil, err
 		}
@@ -42,11 +56,40 @@ func (l Walker) walkMap() (*yaml.RNode, error) {
 }

 // valueIfPresent returns node.Value if node is non-nil, otherwise returns nil
-func (l Walker) valueIfPresent(node *yaml.MapNode) *yaml.RNode {
+func (l Walker) valueIfPresent(node *yaml.MapNode) (*yaml.RNode, *openapi.ResourceSchema) {
 	if node == nil {
-		return nil
+		return nil, nil
 	}
-	return node.Value
+
+	// parse the schema for the field if present
+	var s *openapi.ResourceSchema
+	fm := fieldmeta.FieldMeta{}
+	var err error
+	// check the value for a schema
+	if err = fm.Read(node.Value); err == nil {
+		s = &openapi.ResourceSchema{Schema: &fm.Schema}
+		if fm.Schema.Ref.String() != "" {
+			r, err := openapi.Resolve(&fm.Schema.Ref)
+			if err == nil && r != nil {
+				s.Schema = r
+			}
+		}
+	}
+	// check the key for a schema -- this will be used
+	// when the value is a Sequence (comments are attached)
+	// to the key
+	if fm.IsEmpty() {
+		if err = fm.Read(node.Key); err == nil {
+			s = &openapi.ResourceSchema{Schema: &fm.Schema}
+		}
+		if fm.Schema.Ref.String() != "" {
+			r, err := openapi.Resolve(&fm.Schema.Ref)
+			if err == nil && r != nil {
+				s.Schema = r
+			}
+		}
+	}
+	return node.Value, s
 }

 // fieldNames returns a sorted slice containing the names of all fields that appear in any of
@@ -67,15 +110,20 @@ func (l Walker) fieldNames() []string {
 }

 // fieldValue returns a slice containing each source's value for fieldName
-func (l Walker) fieldValue(fieldName string) []*yaml.RNode {
+func (l Walker) fieldValue(fieldName string) ([]*yaml.RNode, *openapi.ResourceSchema) {
 	var fields []*yaml.RNode
+	var sch *openapi.ResourceSchema
 	for i := range l.Sources {
 		if l.Sources[i] == nil {
 			fields = append(fields, nil)
 			continue
 		}
 		field := l.Sources[i].Field(fieldName)
-		fields = append(fields, l.valueIfPresent(field))
+		f, s := l.valueIfPresent(field)
+		fields = append(fields, f)
+		if sch == nil && !s.IsEmpty() {
+			sch = s
+		}
 	}
-	return fields
+	return fields, sch
 }
--- a/kyaml/yaml/walk/nonassociative_sequence.go
+++ b/kyaml/yaml/walk/nonassociative_sequence.go
@@ -9,5 +9,5 @@ import (

 // walkNonAssociativeSequence returns the value of VisitList
 func (l Walker) walkNonAssociativeSequence() (*yaml.RNode, error) {
-	return l.VisitList(l.Sources, NonAssociateList)
+	return l.VisitList(l.Sources, l.Schema, NonAssociateList)
 }
--- a/kyaml/yaml/walk/scalar.go
+++ b/kyaml/yaml/walk/scalar.go
@@ -7,5 +7,5 @@ import "sigs.k8s.io/kustomize/kyaml/yaml"

 // walkScalar returns the value of VisitScalar
 func (l Walker) walkScalar() (*yaml.RNode, error) {
-	return l.VisitScalar(l.Sources)
+	return l.VisitScalar(l.Sources, l.Schema)
 }
--- a/kyaml/yaml/walk/visitor.go
+++ b/kyaml/yaml/walk/visitor.go
@@ -4,6 +4,7 @@
 package walk

 import (
+	"sigs.k8s.io/kustomize/kyaml/openapi"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
 )

@@ -16,11 +17,11 @@ const (

 // Visitor is invoked by walk with source and destination node pairs
 type Visitor interface {
-	VisitMap(nodes Sources) (*yaml.RNode, error)
+	VisitMap(Sources, *openapi.ResourceSchema) (*yaml.RNode, error)

-	VisitScalar(nodes Sources) (*yaml.RNode, error)
+	VisitScalar(Sources, *openapi.ResourceSchema) (*yaml.RNode, error)

-	VisitList(nodes Sources, kind ListKind) (*yaml.RNode, error)
+	VisitList(Sources, *openapi.ResourceSchema, ListKind) (*yaml.RNode, error)
 }

 // ClearNode is returned if GrepFilter should do nothing after calling Set
--- a/kyaml/yaml/walk/walk.go
+++ b/kyaml/yaml/walk/walk.go
@@ -8,20 +8,30 @@ import (
 	"os"
 	"strings"

+	"sigs.k8s.io/kustomize/kyaml/fieldmeta"
+	"sigs.k8s.io/kustomize/kyaml/openapi"
 	"sigs.k8s.io/kustomize/kyaml/yaml"
+	"sigs.k8s.io/kustomize/kyaml/yaml/schema"
 )

-// Filter walks the Source RNode and modifies the RNode provided to GrepFilter.
+// Walker walks the Source RNode and modifies the RNode provided to GrepFilter.
 type Walker struct {
 	// Visitor is invoked by GrepFilter
 	Visitor

+	Schema *openapi.ResourceSchema
+
 	// Source is the RNode to walk.  All Source fields and associative list elements
 	// will be visited.
 	Sources Sources

 	// Path is the field path to the current Source Node.
 	Path []string
+
+	// InferAssociativeLists if set to true will infer merge strategies for
+	// fields which it doesn't have the schema based on the fields in the
+	// list elements.
+	InferAssociativeLists bool
 }

 func (l Walker) Kind() yaml.Kind {
@@ -35,6 +45,8 @@ func (l Walker) Kind() yaml.Kind {

 // GrepFilter implements yaml.GrepFilter
 func (l Walker) Walk() (*yaml.RNode, error) {
+	l.Schema = l.GetSchema()
+
 	// invoke the handler for the corresponding node type
 	switch l.Kind() {
 	case yaml.MappingNode:
@@ -46,7 +58,7 @@ func (l Walker) Walk() (*yaml.RNode, error) {
 		if err := yaml.ErrorIfAnyInvalidAndNonNull(yaml.SequenceNode, l.Sources...); err != nil {
 			return nil, err
 		}
-		if yaml.IsAssociative(l.Sources) {
+		if schema.IsAssociative(l.Schema, l.Sources, l.InferAssociativeLists) {
 			return l.walkAssociativeSequence()
 		}
 		return l.walkNonAssociativeSequence()
@@ -64,6 +76,49 @@ func (l Walker) Walk() (*yaml.RNode, error) {
 	}
 }

+func (l Walker) GetSchema() *openapi.ResourceSchema {
+	for i := range l.Sources {
+		r := l.Sources[i]
+		if yaml.IsEmpty(r) {
+			continue
+		}
+
+		fm := fieldmeta.FieldMeta{}
+		if err := fm.Read(r); err == nil && !fm.IsEmpty() {
+			// per-field schema, this is fine
+			if fm.Schema.Ref.String() != "" {
+				// resolve the reference
+				s, err := openapi.Resolve(&fm.Schema.Ref)
+				if err == nil && s != nil {
+					fm.Schema = *s
+				}
+			}
+			return &openapi.ResourceSchema{Schema: &fm.Schema}
+		}
+	}
+
+	if l.Schema != nil {
+		return l.Schema
+	}
+	for i := range l.Sources {
+		r := l.Sources[i]
+		if yaml.IsEmpty(r) {
+			continue
+		}
+
+		m, _ := r.GetMeta()
+		if m.Kind == "" || m.APIVersion == "" {
+			continue
+		}
+
+		s := openapi.SchemaForResourceType(yaml.TypeMeta{Kind: m.Kind, APIVersion: m.APIVersion})
+		if s != nil {
+			return s
+		}
+	}
+	return nil
+}
+
 const (
 	DestIndex = iota
 	OriginIndex