ko-build/pkg/resolve/selector.go

// Copyright 2018 Google LLC All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package resolve

import (
	"bytes"
	"fmt"
	"regexp"
	"strings"

	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
	yaml2json "k8s.io/apimachinery/pkg/util/yaml"
	"sigs.k8s.io/yaml"
)

// FilterBySelector filters out any resources
// from the raw manifest bytes whose labels
// don't match the provided selector
func FilterBySelector(input []byte, selectorString string) ([]byte, error) {
	selector, err := labels.Parse(selectorString)
	if err != nil {
		return nil, err
	}

	var outputObjectsYaml [][]byte

	// parse runtime.Objects from the input yaml
	objects, err := parseUnstructured(input)
	if err != nil {
		return nil, err
	}

	for _, object := range objects {
		// objects parsed by UnstructuredJSONScheme can only be of
		// type *unstructured.Unstructured or *unstructured.UnstructuredList
		switch unstructuredObj := object.obj.(type) {
		case *unstructured.Unstructured:
			// append the object if it matches the provided labels
			if selector.Matches(labels.Set(unstructuredObj.GetLabels())) {
				outputObjectsYaml = append(outputObjectsYaml, object.yaml)
			}
		case *unstructured.UnstructuredList:
			// filter the list items based on label
			var filteredItems []unstructured.Unstructured
			for _, obj := range unstructuredObj.Items {
				if selector.Matches(labels.Set(obj.GetLabels())) {
					filteredItems = append(filteredItems, obj)
				}
			}
			// only append the list if it still contains items after being filtered
			switch len(filteredItems) {
			case 0:
				// the whole list was filtered, omit it from the resultant yaml
				continue
			case len(unstructuredObj.Items):
				// nothing was filtered from the list, use the original yaml
				outputObjectsYaml = append(outputObjectsYaml, object.yaml)
			default:
				unstructuredObj.Items = filteredItems
				// list was partially filtered, we need to re-marshal it
				rawJson, err := runtime.Encode(unstructured.UnstructuredJSONScheme, unstructuredObj)
				if err != nil {
					return nil, err
				}
				rawYaml, err := yaml.JSONToYAML(rawJson)
				if err != nil {
					return nil, err
				}
				outputObjectsYaml = append(outputObjectsYaml, rawYaml)
			}
		default:
			panic(fmt.Sprintf("unknown object type %T parsed from yaml: \n%v ", object.obj, object.yaml))
		}
	}

	// re-join the objects into a single manifest
	return bytes.Join(outputObjectsYaml, []byte("\n---")), nil
}

var yamlSeparatorRegex = regexp.MustCompile("\n---")

// a tuple to represent a kubernetes object along with the original yaml snippet it was parsed from
type objectYamlTuple struct {
	obj  runtime.Object
	yaml []byte
}

func parseUnstructured(rawYaml []byte) ([]objectYamlTuple, error) {
	objectYamls := yamlSeparatorRegex.Split(string(rawYaml), -1)

	var resources []objectYamlTuple

	for _, objectYaml := range objectYamls {
		// empty yaml snippets, such as those which can be
		// generated by helm should be ignored
		// else they may be parsed into empty map[string]interface{} objects
		if isEmptyYamlSnippet(objectYaml) {
			continue
		}
		jsn, err := yaml2json.ToJSON([]byte(objectYaml))
		if err != nil {
			return nil, err
		}
		runtimeObj, err := runtime.Decode(unstructured.UnstructuredJSONScheme, jsn)
		if err != nil {
			return nil, err
		}

		resources = append(resources, objectYamlTuple{obj: runtimeObj, yaml: []byte(objectYaml)})
	}

	return resources, nil
}

var commentRegex = regexp.MustCompile("#.*")

func isEmptyYamlSnippet(objYaml string) bool {
	removeComments := commentRegex.ReplaceAllString(objYaml, "")
	removeNewlines := strings.Replace(removeComments, "\n", "", -1)
	removeDashes := strings.Replace(removeNewlines, "---", "", -1)
	removeSpaces := strings.Replace(removeDashes, " ", "", -1)
	return removeSpaces == ""
}