Merge pull request #2454 from monopole/valueAddFilter

add value add filter

api/filters/valueadd/valueadd.go

@@ -0,0 +1,124 @@
+// Copyright 2020 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package valueadd
+
+import (
+	"strings"
+
+	"sigs.k8s.io/kustomize/api/filesys"
+	"sigs.k8s.io/kustomize/kyaml/kio"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+// An 'Add' operation aspiring to IETF RFC 6902 JSON.
+//
+// The filter tries to add a value to a node at a particular field path.
+//
+// Kinds of target fields:
+//
+// - Non-existent target field.
+//
+//   The field will be added and the value inserted.
+//
+// - Existing field, scalar or map.
+//
+//   E.g. 'spec/template/spec/containers/[name:nginx]/image'
+//
+//   This behaves like an IETF RFC 6902 Replace operation would;
+//   the existing value is replaced without complaint, even though
+//   this  is an Add operation.  In contrast, a Replace operation
+//   must fail (report an error) if the field doesn't exist.
+//
+// - Existing field, list (array)
+//   Not supported yet.
+//   TODO: Honor fields with RFC-6902-style array indices
+//   TODO: like 'spec/template/spec/containers/2'
+//   TODO: Modify kyaml/yaml/PathGetter to allow this.
+//   The value will be inserted into the array at the given position,
+//   shifting other contents. To instead replace an array entry, use
+//   an implementation of an IETF RFC 6902 Replace operation.
+//
+// For the common case of a filepath in the field value, and a desire
+// to add the value to the filepath (rather than replace the filepath),
+// use a non-zero value of FilePathPosition (see below).
+type Filter struct {
+	// Value is the value to add.
+	//
+	// Empty values are disallowed, i.e. this filter isn't intended
+	// for use in erasing or removing fields. For that, use a filter
+	// more aligned with the IETF RFC 6902 JSON Remove operation.
+	//
+	// At the time of writing, Value's value should be a simple string,
+	// not a JSON document.  This particular filter focuses on easing
+	// injection of a single-sourced cloud project and/or cluster name
+	// into various fields, especially namespace and various filepath
+	// specifications.
+	Value string
+
+	// FieldPath is a JSON-style path to the field intended to hold the value.
+	FieldPath string
+
+	// FilePathPosition is a filepath field index.
+	//
+	// Call the value of this field _i_.
+	//
+	//   If _i_ is zero, negative or unspecified, this field has no effect.
+	//
+	//   If _i_ is > 0, then it's assumed that
+	//   - 'Value' is a string that can work as a directory or file name,
+	//   - the field value intended for replacement holds a filepath.
+	//
+	// The filepath is split into a string slice, the value is inserted
+	// at position [i-1], shifting the rest of the path to the right.
+	// A value of i==1 puts the new value at the start of the path.
+	// This change never converts an absolute path to a relative path,
+	// meaning adding a new field at position i==1 will preserve a
+	// leading slash. E.g. if Value == 'PEACH'
+	//
+	//                  OLD : NEW                    : FilePathPosition
+	//      --------------------------------------------------------
+	//              {empty} : PEACH                  : irrelevant
+	//                    / : /PEACH                 : irrelevant
+	//                  pie : PEACH/pie              : 1 (or less to prefix)
+	//                 /pie : /PEACH/pie             : 1 (or less to prefix)
+	//                  raw : raw/PEACH              : 2 (or more to postfix)
+	//                 /raw : /raw/PEACH             : 2 (or more to postfix)
+	//      a/nice/warm/pie : a/nice/warm/PEACH/pie  : 4
+	//     /a/nice/warm/pie : /a/nice/warm/PEACH/pie : 4
+	//
+	// For robustness (liberal input, conservative output) FilePathPosition
+	// values that that are too large to index the split filepath result in a
+	// postfix rather than an error.  So use 1 to prefix, 9999 to postfix.
+	FilePathPosition int `json:"filePathPosition,omitempty" yaml:"filePathPosition,omitempty"`
+}
+
+var _ kio.Filter = Filter{}
+
+func (f Filter) Filter(nodes []*yaml.RNode) ([]*yaml.RNode, error) {
+	_, err := kio.FilterAll(yaml.FilterFunc(
+		func(node *yaml.RNode) (*yaml.RNode, error) {
+			fields := strings.Split(f.FieldPath, "/")
+			// TODO: support SequenceNode.
+			// Presumably here one could look for array indices (digits) at
+			// the end of the field path (as described in IETF RFC 6902 JSON),
+			// and if found, take it as a signal that this should be a
+			// SequenceNode instead of a ScalarNode, and insert the value
+			// into the proper slot, shifting every over.
+			n, err := node.Pipe(yaml.LookupCreate(yaml.ScalarNode, fields...))
+			if err != nil {
+				return node, err
+			}
+			// TODO: allow more kinds
+			if err := yaml.ErrorIfInvalid(n, yaml.ScalarNode); err != nil {
+				return nil, err
+			}
+			newValue := f.Value
+			if f.FilePathPosition > 0 {
+				newValue = filesys.InsertPathPart(
+					n.YNode().Value, f.FilePathPosition-1, newValue)
+			}
+			return n.Pipe(yaml.FieldSetter{StringValue: newValue})
+		})).Filter(nodes)
+	return nodes, err
+}

api/filters/valueadd/valueadd_test.go

@@ -0,0 +1,109 @@
+// Copyright 2020 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package valueadd
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	filtertest_test "sigs.k8s.io/kustomize/api/testutils/filtertest"
+)
+
+const someResource = `
+kind: SomeKind
+spec:
+  resourceRef:
+    external: projects/whatever
+`
+
+func TestValueAddFilter(t *testing.T) {
+	testCases := map[string]struct {
+		input          string
+		expectedOutput string
+		filter         Filter
+	}{
+		"simpleAdd": {
+			input: `
+kind: SomeKind
+`,
+			expectedOutput: `
+kind: SomeKind
+spec:
+  resourceRef:
+    external: valueAdded
+`,
+			filter: Filter{
+				Value:     "valueAdded",
+				FieldPath: "spec/resourceRef/external",
+			},
+		},
+		"replaceExisting": {
+			input: someResource,
+			expectedOutput: `
+kind: SomeKind
+spec:
+  resourceRef:
+    external: valueAdded
+`,
+			filter: Filter{
+				Value:     "valueAdded",
+				FieldPath: "spec/resourceRef/external",
+			},
+		},
+		"prefixExisting": {
+			input: someResource,
+			expectedOutput: `
+kind: SomeKind
+spec:
+  resourceRef:
+    external: valueAdded/projects/whatever
+`,
+			filter: Filter{
+				Value:            "valueAdded",
+				FieldPath:        "spec/resourceRef/external",
+				FilePathPosition: 1,
+			},
+		},
+		"postfixExisting": {
+			input: someResource,
+			expectedOutput: `
+kind: SomeKind
+spec:
+  resourceRef:
+    external: projects/whatever/valueAdded
+`,
+			filter: Filter{
+				Value:            "valueAdded",
+				FieldPath:        "spec/resourceRef/external",
+				FilePathPosition: 99,
+			},
+		},
+		"placeInMiddleOfExisting": {
+			input: someResource,
+			expectedOutput: `
+kind: SomeKind
+spec:
+  resourceRef:
+    external: projects/valueAdded/whatever
+`,
+			filter: Filter{
+				Value:            "valueAdded",
+				FieldPath:        "spec/resourceRef/external",
+				FilePathPosition: 2,
+			},
+		},
+	}
+
+	for tn, tc := range testCases {
+		t.Run(tn, func(t *testing.T) {
+			filter := tc.filter
+			if !assert.Equal(t,
+				strings.TrimSpace(tc.expectedOutput),
+				strings.TrimSpace(filtertest_test.RunFilter(t, tc.input, filter))) {
+				t.FailNow()
+			}
+		})
+	}
+}