add replacement filter to support replacmenttransformer

api/filters/replacement/doc.go

@@ -0,0 +1,4 @@
+// Package replacement contains a kio.Filter implementation of the kustomize
+// replacement transformer (accepts sources and looks for targets to replace
+// their values with values form the sources).
+package replacement

api/filters/replacement/example_test.go

@@ -0,0 +1,56 @@
+// Copyright 2020 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package replacement
+
+import (
+	"bytes"
+	"log"
+	"os"
+
+	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/kio"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+func ExampleFilter() {
+	f := Filter{
+		Replacements: []types.Replacement{},
+	}
+	err := yaml.Unmarshal([]byte(`
+replacements:
+- source:
+    value: 99
+  target:
+    objref:
+      kind: Foo
+    fieldrefs:
+    - spec.replicas`), &f)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = kio.Pipeline{
+		Inputs: []kio.Reader{&kio.ByteReader{Reader: bytes.NewBufferString(`
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  replicas: 3
+`)}},
+		Filters: []kio.Filter{f},
+		Outputs: []kio.Writer{kio.ByteWriter{Writer: os.Stdout}},
+	}.Execute()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Output:
+	// apiVersion: example.com/v1
+	// kind: Foo
+	// metadata:
+	//   name: instance
+	// spec:
+	//   replicas: 99
+}

api/filters/replacement/replacement.go

@@ -0,0 +1,111 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package replacement
+
+import (
+	"fmt"
+	"strings"
+
+	"sigs.k8s.io/kustomize/api/provider"
+	"sigs.k8s.io/kustomize/api/resmap"
+	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/kio"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+type Filter struct {
+	Replacements []types.Replacement
+}
+
+var _ kio.Filter = Filter{}
+
+// Filter replaces values of targets with values from sources
+// TODO (#3492): Connect this to a replacement transformer plugin
+func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
+	var result []*yaml.RNode
+	// TODO (#3492): Move getReplacement to the replacement transformer plugin
+	//   and avoid creating a new resmap here
+	rf := provider.NewDefaultDepProvider().GetResourceFactory()
+	m, err := resmap.NewFactory(rf).NewResMapFromRNodeSlice(nodes)
+	if err != nil {
+		return nil, err
+	}
+	for i := range nodes {
+		r, err := applyReplacements(f.Replacements, nodes[i], m)
+		if err != nil {
+			return nil, err
+		}
+		if r != nil {
+			result = append(result, r)
+		}
+	}
+	return result, nil
+}
+
+func applyReplacements(replacements []types.Replacement, node *yaml.RNode,
+	m resmap.ResMap) (*yaml.RNode, error) {
+	for _, r := range replacements {
+		value, err := getReplacement(m, r.Source)
+		if err != nil {
+			return node, err
+		}
+		node, err := applyReplacement(r, node, value)
+		if err != nil {
+			return node, err
+		}
+	}
+	return node, nil
+}
+
+func applyReplacement(r types.Replacement, node *yaml.RNode, value *yaml.RNode) (*yaml.RNode, error) {
+	for i := range r.Target.FieldRefs {
+		fieldref := strings.Split(r.Target.FieldRefs[i], ".")
+		// TODO (#3492): Support using map keys in the fieldref (e.g. .spec.containers[name=nginx])
+		target, err := node.Pipe(yaml.Lookup(fieldref...))
+		if err != nil {
+			return node, err
+		}
+		if target == nil {
+			continue
+		}
+		target.SetYNode(value.YNode())
+	}
+	return node, nil
+}
+
+// TODO (#3492): Move this to the replacement transformer plugin, and have it pass the
+//   source value to the filter. The plugin will already have a ResMap so it will not
+//   need to convert the nodes to a ResMap.
+func getReplacement(m resmap.ResMap, source *types.ReplSource) (*yaml.RNode, error) {
+	if source.Value != "" {
+		return yaml.Parse(source.Value)
+	}
+	objRef := source.ObjRef
+	fieldRef := source.FieldRef
+	s := types.Selector{
+		Gvk:       objRef.Gvk,
+		Name:      objRef.Name,
+		Namespace: objRef.Namespace,
+	}
+	resources, err := m.Select(s)
+	if err != nil {
+		return nil, err
+	}
+	if len(resources) > 1 {
+		return nil, fmt.Errorf("found more than one resources matching from %v", resources)
+	}
+	if len(resources) == 0 {
+		return nil, fmt.Errorf("failed to find one resource matching from %v", objRef)
+	}
+	if fieldRef == "" {
+		fieldRef = ".metadata.name"
+	}
+	fieldRefSlice := strings.Split(fieldRef, ".")
+	// TODO (#3492): Support using map keys in the fieldref (e.g. .spec.containers[name=nginx])
+	rn, err := resources[0].AsRNode().Pipe(yaml.Lookup(fieldRefSlice...))
+	if err != nil {
+		return nil, err
+	}
+	return rn, nil
+}