From 1abdefd8c082401a3f7a9044046c0ced20d3f13f Mon Sep 17 00:00:00 2001
From: Sean Sullivan <seans@google.com>
Date: Wed, 19 Jun 2019 17:13:57 -0700
Subject: [PATCH] Move pkg/kubectl/util/fieldpath to staging

Kubernetes-commit: 6274ef995f2cb8a609a83e77a96623021e9299a5
---
 pkg/util/fieldpath/fieldpath.go | 111 ++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 pkg/util/fieldpath/fieldpath.go

diff --git a/pkg/util/fieldpath/fieldpath.go b/pkg/util/fieldpath/fieldpath.go
new file mode 100644
index 000000000..efd08cde0
--- /dev/null
+++ b/pkg/util/fieldpath/fieldpath.go
@@ -0,0 +1,111 @@
+/*
+Copyright 2015 The Kubernetes Authors.
+
+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 fieldpath
+
+import (
+	"fmt"
+	"strings"
+
+	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/apimachinery/pkg/util/validation"
+)
+
+// TODO(yue9944882): Remove this helper package once it's copied to k/apimachinery
+
+// FormatMap formats map[string]string to a string.
+func FormatMap(m map[string]string) (fmtStr string) {
+	// output with keys in sorted order to provide stable output
+	keys := sets.NewString()
+	for key := range m {
+		keys.Insert(key)
+	}
+	for _, key := range keys.List() {
+		fmtStr += fmt.Sprintf("%v=%q\n", key, m[key])
+	}
+	fmtStr = strings.TrimSuffix(fmtStr, "\n")
+
+	return
+}
+
+// ExtractFieldPathAsString extracts the field from the given object
+// and returns it as a string.  The object must be a pointer to an
+// API type.
+func ExtractFieldPathAsString(obj interface{}, fieldPath string) (string, error) {
+	accessor, err := meta.Accessor(obj)
+	if err != nil {
+		return "", nil
+	}
+
+	if path, subscript, ok := SplitMaybeSubscriptedPath(fieldPath); ok {
+		switch path {
+		case "metadata.annotations":
+			if errs := validation.IsQualifiedName(strings.ToLower(subscript)); len(errs) != 0 {
+				return "", fmt.Errorf("invalid key subscript in %s: %s", fieldPath, strings.Join(errs, ";"))
+			}
+			return accessor.GetAnnotations()[subscript], nil
+		case "metadata.labels":
+			if errs := validation.IsQualifiedName(subscript); len(errs) != 0 {
+				return "", fmt.Errorf("invalid key subscript in %s: %s", fieldPath, strings.Join(errs, ";"))
+			}
+			return accessor.GetLabels()[subscript], nil
+		default:
+			return "", fmt.Errorf("fieldPath %q does not support subscript", fieldPath)
+		}
+	}
+
+	switch fieldPath {
+	case "metadata.annotations":
+		return FormatMap(accessor.GetAnnotations()), nil
+	case "metadata.labels":
+		return FormatMap(accessor.GetLabels()), nil
+	case "metadata.name":
+		return accessor.GetName(), nil
+	case "metadata.namespace":
+		return accessor.GetNamespace(), nil
+	case "metadata.uid":
+		return string(accessor.GetUID()), nil
+	}
+
+	return "", fmt.Errorf("unsupported fieldPath: %v", fieldPath)
+}
+
+// SplitMaybeSubscriptedPath checks whether the specified fieldPath is
+// subscripted, and
+//  - if yes, this function splits the fieldPath into path and subscript, and
+//    returns (path, subscript, true).
+//  - if no, this function returns (fieldPath, "", false).
+//
+// Example inputs and outputs:
+//  - "metadata.annotations['myKey']" --> ("metadata.annotations", "myKey", true)
+//  - "metadata.annotations['a[b]c']" --> ("metadata.annotations", "a[b]c", true)
+//  - "metadata.labels['']"           --> ("metadata.labels", "", true)
+//  - "metadata.labels"               --> ("metadata.labels", "", false)
+func SplitMaybeSubscriptedPath(fieldPath string) (string, string, bool) {
+	if !strings.HasSuffix(fieldPath, "']") {
+		return fieldPath, "", false
+	}
+	s := strings.TrimSuffix(fieldPath, "']")
+	parts := strings.SplitN(s, "['", 2)
+	if len(parts) < 2 {
+		return fieldPath, "", false
+	}
+	if len(parts[0]) == 0 {
+		return fieldPath, "", false
+	}
+	return parts[0], parts[1], true
+}