Fix error during expansion of !!merge <<: anchor tags (#4383)

* WIP

* Fix merge corner cases

* Add test for explicit !!merge tag

* Fix tests

* Cleanup

* Cleanup

* Fix deanchoring lists

* Add test case for keeping comments

* Add MapEntrySetter and fix json marshalling after deanchoring

* Keep duplicated keys

* Move MergeTag definition to yaml alias

* Remove go-spew from api

* Add support for sequence nodes on merge tags

* Add docstring to MapEntrySetter.Key

* Add docstring to MapEntrySetter struct

* Add tests to MapEntrySetter

* Fix duplicate merge key

* Revert whitespace changes on forked go-yaml

* Remove AssocMapEntry function

* Refactoring merge order

* Return errors on VisitFields and PipeE

* Add tests for each non-conforming map merges

api/resmap/reswrangler_test.go

@@ -958,6 +958,53 @@ metadata:
 `), strings.TrimSpace(string(yaml)))
 }
 
+func TestDeAnchorIntoDoc(t *testing.T) {
+	input := `apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: probes-test
+spec:
+  template:
+    spec:
+      readinessProbe: &probe
+        periodSeconds: 5
+        timeoutSeconds: 3
+        failureThreshold: 3
+        httpGet:
+          port: http
+          path: /health
+      livenessProbe:
+        <<: *probe
+`
+	rm, err := rmF.NewResMapFromBytes([]byte(input))
+	assert.NoError(t, err)
+	assert.NoError(t, rm.DeAnchor())
+	yaml, err := rm.AsYaml()
+	assert.NoError(t, err)
+	assert.Equal(t, strings.TrimSpace(`apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: probes-test
+spec:
+  template:
+    spec:
+      livenessProbe:
+        failureThreshold: 3
+        httpGet:
+          path: /health
+          port: http
+        periodSeconds: 5
+        timeoutSeconds: 3
+      readinessProbe:
+        failureThreshold: 3
+        httpGet:
+          path: /health
+          port: http
+        periodSeconds: 5
+        timeoutSeconds: 3
+`), strings.TrimSpace(string(yaml)))
+}
+
 // Anchor references don't cross YAML document boundaries.
 func TestDeAnchorMultiDoc(t *testing.T) {
 	input := `apiVersion: v1

api/resource/factory_test.go

@@ -335,13 +335,7 @@ kind: List
 		"listWithAnchorReference": {
 			input:       []types.PatchStrategicMerge{patchList2},
 			expectedOut: []*Resource{testDeploymentA, testDeploymentB},
-			// The error using kyaml is:
-			//   json: unsupported type: map[interface {}]interface {}
-			// maybe arising from too many conversions between
-			// yaml, json, Resource, RNode, etc.
-			// These conversions go away after closing #3506
-			// TODO(#3271) This shouldn't have an error, but does when kyaml is used.
-			expectedErr: true,
+			expectedErr: false,
 		},
 		"listWithNoEntries": {
 			input:       []types.PatchStrategicMerge{patchList3},

kyaml/kio/byteio_reader_test.go

@@ -743,7 +743,7 @@ items:
 `},
 			},
 		},
-		"listWithAnchors": {
+		"mergeAnchors": {
 			input: []byte(`
 apiVersion: v1
 kind: DeploymentList
@@ -764,7 +764,59 @@ items:
   metadata:
     name: deployment-b
   spec:
-    *hostAliases
+    <<: *hostAliases
+`),
+			exp: expected{
+				sOut: []string{`
+apiVersion: v1
+kind: DeploymentList
+items:
+- apiVersion: apps/v1
+  kind: Deployment
+  metadata:
+    name: deployment-a
+  spec:
+    template:
+      spec:
+        hostAliases:
+        - hostnames:
+          - a.example.com
+          ip: 8.8.8.8
+- apiVersion: apps/v1
+  kind: Deployment
+  metadata:
+    name: deployment-b
+  spec:
+    template:
+      spec:
+        hostAliases:
+        - hostnames:
+          - a.example.com
+          ip: 8.8.8.8
+`},
+			},
+		},
+		"listWithAnchors": {
+			input: []byte(`
+apiVersion: v1
+kind: DeploymentList
+items:
+- apiVersion: apps/v1
+  kind: Deployment
+  metadata:
+    name: deployment-a
+  spec: &hostAliases
+    template:
+      spec:
+        hostAliases:
+        - hostnames:
+          - a.example.com
+          ip: 8.8.8.8
+- apiVersion: apps/v1
+  kind: Deployment
+  metadata:
+    name: deployment-b
+  spec: *hostAliases
 `),
 			exp: expected{
 				sOut: []string{`

kyaml/yaml/alias.go

@@ -93,3 +93,7 @@ var FoldedStyle yaml.Style = yaml.FoldedStyle
 var LiteralStyle yaml.Style = yaml.LiteralStyle
 var SingleQuotedStyle yaml.Style = yaml.SingleQuotedStyle
 var TaggedStyle yaml.Style = yaml.TaggedStyle
+
+const (
+	MergeTag = "!!merge"
+)

kyaml/yaml/fns.go

@@ -612,6 +612,50 @@ func Set(value *RNode) FieldSetter {
 	return FieldSetter{Value: value}
 }
 
+// MapEntrySetter sets a map entry to a value. If it finds a key with the same
+// value, it will override both Key and Value RNodes, including style and any
+// other metadata. If it doesn't find the key, it will insert a new map entry.
+// It will set the field, even if it's empty or nil, unlike the FieldSetter.
+// This is useful for rebuilding some pre-existing RNode structure.
+type MapEntrySetter struct {
+	// Name is the name of the field or key to lookup in a MappingNode.
+	// If Name is unspecified, it will use the Key's Value
+	Name string `yaml:"name,omitempty"`
+
+	// Value is the value to set.
+	Value *RNode `yaml:"value,omitempty"`
+
+	// Key is the map key to set.
+	Key *RNode `yaml:"key,omitempty"`
+}
+
+func (s MapEntrySetter) Filter(rn *RNode) (*RNode, error) {
+	if rn == nil {
+		return nil, errors.Errorf("Can't set map entry on a nil RNode")
+	}
+	if err := ErrorIfInvalid(rn, yaml.MappingNode); err != nil {
+		return nil, err
+	}
+	if s.Name == "" {
+		s.Name = GetValue(s.Key)
+	}
+	for i := 0; i < len(rn.Content()); i = IncrementFieldIndex(i) {
+		isMatchingField := rn.Content()[i].Value == s.Name
+		if isMatchingField {
+			rn.Content()[i] = s.Key.YNode()
+			rn.Content()[i+1] = s.Value.YNode()
+			return rn, nil
+		}
+	}
+
+	// create the field
+	rn.YNode().Content = append(
+		rn.YNode().Content,
+		s.Key.YNode(),
+		s.Value.YNode())
+	return rn, nil
+}
+
 // FieldSetter sets a field or map entry to a value.
 type FieldSetter struct {
 	Kind string `yaml:"kind,omitempty"`

kyaml/yaml/fns_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"sigs.k8s.io/kustomize/kyaml/errors"
 	"sigs.k8s.io/kustomize/kyaml/internal/forked/github.com/go-yaml/yaml"
 	. "sigs.k8s.io/kustomize/kyaml/yaml"
 )
@@ -791,6 +792,83 @@ spec:
 	}
 }
 
+func TestMapEntrySetter(t *testing.T) {
+	withStyle := func(rn *RNode, style yaml.Style) *RNode {
+		rn.YNode().Style = style
+		return rn
+	}
+	testCases := []struct {
+		desc        string
+		input       string
+		setter      MapEntrySetter
+		expected    string
+		expectedErr error
+	}{
+		{
+			desc:  "it should override Key's value map entry",
+			input: "foo: baz\n",
+			setter: MapEntrySetter{
+				Key:   NewScalarRNode("foo"),
+				Value: NewScalarRNode("bar"),
+			},
+			expected: "foo: bar\n",
+		},
+		{
+			desc:  "it should override Name's map entry",
+			input: "foo: baz\n",
+			setter: MapEntrySetter{
+				Name:  "foo",
+				Key:   NewScalarRNode("bar"),
+				Value: NewScalarRNode("baz"),
+			},
+			expected: "bar: baz\n",
+		},
+		{
+			desc:  "it should insert new map entry",
+			input: "foo: baz\n",
+			setter: MapEntrySetter{
+				Key:   NewScalarRNode("bar"),
+				Value: NewScalarRNode("42"),
+			},
+			expected: "foo: baz\nbar: 42\n",
+		},
+		{
+			desc:  "it should override the style",
+			input: "foo: baz\n",
+			setter: MapEntrySetter{
+				Key:   withStyle(NewScalarRNode("foo"), yaml.DoubleQuotedStyle),
+				Value: withStyle(NewScalarRNode("bar"), yaml.SingleQuotedStyle),
+			},
+			expected: `"foo": 'bar'` + "\n",
+		},
+		{
+			desc:  "it should return error on sequence nodes",
+			input: "- foo: baz\n",
+			setter: MapEntrySetter{
+				Key:   NewScalarRNode("foo"),
+				Value: NewScalarRNode("bar"),
+			},
+			expectedErr: errors.Errorf("wrong Node Kind for  expected: MappingNode was SequenceNode: value: {- foo: baz}"),
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.desc, func(t *testing.T) {
+			node, err := Parse(tc.input)
+			assert.NoError(t, err)
+			k, err := tc.setter.Filter(node)
+			if tc.expectedErr == nil {
+				assert.NoError(t, err)
+				assert.Equal(t, tc.expected, assertNoErrorString(t)(node.String()))
+				assert.Equal(t, tc.expected, assertNoErrorString(t)(k.String()))
+			} else {
+				assert.NotNil(t, err)
+				assert.Equal(t, tc.expectedErr.Error(), err.Error())
+			}
+
+		})
+	}
+}
+
 func TestFieldSetter(t *testing.T) {
 	// Change field
 	node, err := Parse(`