kyaml: initial support for yaml and resource manipulation

kyaml/yaml/merge2/merge2.go

@@ -0,0 +1,201 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package merge contains libraries for merging fields from one RNode to another
+// RNode
+package merge2
+
+import (
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+	"sigs.k8s.io/kustomize/kyaml/yaml/walk"
+)
+
+const Help = `
+Description:
+
+  merge merges fields from a source to a destination, overriding the destination fields
+  where they differ.
+
+  ### Merge Rules
+
+  Fields are recursively merged using the following rules:
+
+  - scalars
+    - if present only in the dest, it keeps its value
+    - if present in the src and is non-null, take the src value -- if ` + "`null`" + `, clear it
+` + "    - example src: `5`, dest: `3` => result: `5`" + `
+
+  - non-associative lists -- lists without a merge key
+    - if present only in the dest, it keeps its value
+    - if present in the src and is non-null, take the src value -- if ` + "`null`" + `, clear it
+` + "    - example src: `[1, 2, 3]`, dest: `[a, b, c]` => result: `[1, 2, 3]`" + `
+
+  - map keys and fields -- paired by the map-key / field-name
+    - if present only in the dest, it keeps its value
+    - if present only in the src, it is added to the dest
+    - if the field is present in both the src and dest, and the src value is 'null', the field is removed from the dest
+    - if the field is present in both the src and dest, the value is recursively merged
+` + "    - example src: `{'key1': 'value1', 'key2': 'value2'}`, dest: `{'key2': 'value0', 'key3': 'value3'}` => result: `{'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}`" + `
+
+  - associative list elements -- paired by the associative key
+    - if present only in the dest, it keeps its value in the list
+    - if present only in the src, it is added to the dest list
+    - if the field is present in both the src and dest, the value is recursively merged
+
+  ### Associative Keys
+
+  Associative keys are used to identify "same" elements within 2 different lists, and merge them.
+  The following fields are recognized as associative keys:
+
+` + "[`mountPath`, `devicePath`, `ip`, `type`, `topologyKey`, `name`, `containerPort`]" + `
+
+  Any lists where all of the elements contain associative keys will be merged as associative lists.
+
+  ### Example
+
+  > Source
+
+	apiVersion: apps/v1
+	kind: Deployment
+	spec:
+	  replicas: 3 # scalar
+	  template:
+	    spec:
+	      containers:  # associative list -- (name)
+	      - name: nginx
+	        image: nginx:1.7
+	        command: ['new_run.sh', 'arg1'] # non-associative list
+	      - name: sidecar2
+	        image: sidecar2:v1
+
+  > Destination
+
+	apiVersion: apps/v1
+	kind: Deployment
+	spec:
+	  replicas: 1
+	  template:
+	    spec:
+	      containers:
+	      - name: nginx
+	        image: nginx:1.6
+	        command: ['old_run.sh', 'arg0']
+	      - name: sidecar1
+	        image: sidecar1:v1
+
+  > Result
+
+	apiVersion: apps/v1
+	kind: Deployment
+	spec:
+	  replicas: 3 # scalar
+	  template:
+	    spec:
+	      containers:  # associative list -- (name)
+	      - name: nginx
+	        image: nginx:1.7
+	        command: ['new_run.sh', 'arg1'] # non-associative list
+	      - name: sidecar1
+	        image: sidecar1:v1
+	      - name: sidecar2
+	        image: sidecar2:v1
+`
+
+// Merge merges fields from src into dest.
+func Merge(src, dest *yaml.RNode) (*yaml.RNode, error) {
+	return walk.Walker{Sources: []*yaml.RNode{dest, src}, Visitor: Merger{}}.Walk()
+}
+
+// Merge parses the arguments, and merges fields from srcStr into destStr.
+func MergeStrings(srcStr, destStr string) (string, error) {
+	src, err := yaml.Parse(srcStr)
+	if err != nil {
+		return "", err
+	}
+	dest, err := yaml.Parse(destStr)
+	if err != nil {
+		return "", err
+	}
+
+	result, err := Merge(src, dest)
+	if err != nil {
+		return "", err
+	}
+	return result.String()
+}
+
+type Merger struct {
+	// for forwards compatibility when new functions are added to the interface
+}
+
+var _ walk.Visitor = Merger{}
+
+func (m Merger) VisitMap(nodes walk.Sources) (*yaml.RNode, error) {
+	if err := m.SetComments(nodes); err != nil {
+		return nil, err
+	}
+	if yaml.IsEmpty(nodes.Dest()) {
+		// Add
+		return nodes.Origin(), nil
+	}
+	if yaml.IsNull(nodes.Origin()) {
+		// clear the value
+		return walk.ClearNode, nil
+	}
+	// Recursively Merge dest
+	return nodes.Dest(), nil
+}
+
+func (m Merger) VisitScalar(nodes walk.Sources) (*yaml.RNode, error) {
+	if err := m.SetComments(nodes); err != nil {
+		return nil, err
+	}
+	// Override value
+	if nodes.Origin() != nil {
+		return nodes.Origin(), nil
+	}
+	// Keep
+	return nodes.Dest(), nil
+}
+
+func (m Merger) VisitList(nodes walk.Sources, kind walk.ListKind) (*yaml.RNode, error) {
+	if err := m.SetComments(nodes); err != nil {
+		return nil, err
+	}
+	if kind == walk.NonAssociateList {
+		// Override value
+		if nodes.Origin() != nil {
+			return nodes.Origin(), nil
+		}
+		// Keep
+		return nodes.Dest(), nil
+	}
+
+	// Add
+	if yaml.IsEmpty(nodes.Dest()) {
+		return nodes.Origin(), nil
+	}
+	// Clear
+	if yaml.IsNull(nodes.Origin()) {
+		return walk.ClearNode, nil
+	}
+	// Recursively Merge dest
+	return nodes.Dest(), nil
+}
+
+// SetComments copies the dest comments to the source comments if they are present
+// on the source.
+func (m Merger) SetComments(sources walk.Sources) error {
+	source := sources.Origin()
+	dest := sources.Dest()
+	if source != nil && source.YNode().FootComment != "" {
+		dest.YNode().FootComment = source.YNode().FootComment
+	}
+	if source != nil && source.YNode().HeadComment != "" {
+		dest.YNode().HeadComment = source.YNode().HeadComment
+	}
+	if source != nil && source.YNode().LineComment != "" {
+		dest.YNode().LineComment = source.YNode().LineComment
+	}
+	return nil
+}