Merge pull request #50579 from erhudy/bugfix/29271-accept-prefixed-namespaces

Automatic merge from submit-queue

Fixes kubernetes/kubernetes#29271: accept prefixed namespaces

**What this PR does / why we need it**: `kubectl get namespaces -o name` outputs the names of all namespaces, prefixed with `namespaces/`. This changeset allows these namespace names to be passed directly back in to `kubectl` via the `-n` flag without reprocessing them to remove `namespaces/`.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #29271

**Special notes for your reviewer**:

**Release note**:

```NONE
```

Kubernetes-commit: ab27bc9e6e020fc475b4872a6c049ac7fe91edbb

tools/clientcmd/BUILD

@@ -12,12 +12,14 @@ go_test(
         "client_config_test.go",
         "loader_test.go",
         "merged_client_builder_test.go",
+        "overrides_test.go",
         "validation_test.go",
     ],
     library = ":go_default_library",
     deps = [
         "//vendor/github.com/ghodss/yaml:go_default_library",
         "//vendor/github.com/imdario/mergo:go_default_library",
+        "//vendor/github.com/spf13/pflag:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/errors:go_default_library",
         "//vendor/k8s.io/client-go/rest:go_default_library",
@@ -33,6 +35,7 @@ go_library(
         "client_config.go",
         "config.go",
         "doc.go",
+        "flag.go",
         "helpers.go",
         "loader.go",
         "merged_client_builder.go",

tools/clientcmd/flag.go

@@ -0,0 +1,49 @@
+/*
+Copyright 2017 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 clientcmd
+
+// transformingStringValue implements pflag.Value to store string values,
+// allowing transforming them while being set
+type transformingStringValue struct {
+	target      *string
+	transformer func(string) (string, error)
+}
+
+func newTransformingStringValue(val string, target *string, transformer func(string) (string, error)) *transformingStringValue {
+	*target = val
+	return &transformingStringValue{
+		target:      target,
+		transformer: transformer,
+	}
+}
+
+func (t *transformingStringValue) Set(val string) error {
+	val, err := t.transformer(val)
+	if err != nil {
+		return err
+	}
+	*t.target = val
+	return nil
+}
+
+func (t *transformingStringValue) Type() string {
+	return "string"
+}
+
+func (t *transformingStringValue) String() string {
+	return string(*t.target)
+}

tools/clientcmd/overrides.go

@@ -18,6 +18,7 @@ package clientcmd
 
 import (
 	"strconv"
+	"strings"
 
 	"github.com/spf13/pflag"
 
@@ -101,6 +102,15 @@ func (f FlagInfo) BindStringFlag(flags *pflag.FlagSet, target *string) FlagInfo
 	return f
 }
 
+// BindTransformingStringFlag binds the flag based on the provided info.  If LongName == "", nothing is registered
+func (f FlagInfo) BindTransformingStringFlag(flags *pflag.FlagSet, target *string, transformer func(string) (string, error)) FlagInfo {
+	// you can't register a flag without a long name
+	if len(f.LongName) > 0 {
+		flags.VarP(newTransformingStringValue(f.Default, target, transformer), f.LongName, f.ShortName, f.Description)
+	}
+	return f
+}
+
 // BindStringSliceFlag binds the flag based on the provided info.  If LongName == "", nothing is registered
 func (f FlagInfo) BindStringArrayFlag(flags *pflag.FlagSet, target *[]string) FlagInfo {
 	// you can't register a flag without a long name
@@ -222,5 +232,16 @@ func BindClusterFlags(clusterInfo *clientcmdapi.Cluster, flags *pflag.FlagSet, f
 func BindContextFlags(contextInfo *clientcmdapi.Context, flags *pflag.FlagSet, flagNames ContextOverrideFlags) {
 	flagNames.ClusterName.BindStringFlag(flags, &contextInfo.Cluster)
 	flagNames.AuthInfoName.BindStringFlag(flags, &contextInfo.AuthInfo)
-	flagNames.Namespace.BindStringFlag(flags, &contextInfo.Namespace)
+	flagNames.Namespace.BindTransformingStringFlag(flags, &contextInfo.Namespace, RemoveNamespacesPrefix)
+}
+
+// RemoveNamespacesPrefix is a transformer that strips "ns/", "namespace/" and "namespaces/" prefixes case-insensitively
+func RemoveNamespacesPrefix(value string) (string, error) {
+	for _, prefix := range []string{"namespaces/", "namespace/", "ns/"} {
+		if len(value) > len(prefix) && strings.EqualFold(value[0:len(prefix)], prefix) {
+			value = value[len(prefix):]
+			break
+		}
+	}
+	return value, nil
 }

tools/clientcmd/overrides_test.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2017 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 clientcmd
+
+import (
+	"testing"
+
+	"github.com/spf13/pflag"
+)
+
+func TestNamespacePrefixStrip(t *testing.T) {
+	testData := map[string]string{
+		"namespaces/foo": "foo",
+		"NAMESPACES/foo": "foo",
+		"NameSpaces/foo": "foo",
+		"namespace/foo":  "foo",
+		"NAMESPACE/foo":  "foo",
+		"nameSpace/foo":  "foo",
+		"ns/foo":         "foo",
+		"NS/foo":         "foo",
+		"namespaces/":    "namespaces/",
+		"namespace/":     "namespace/",
+		"ns/":            "ns/",
+	}
+
+	for before, after := range testData {
+		overrides := &ConfigOverrides{}
+		fs := &pflag.FlagSet{}
+		BindOverrideFlags(overrides, fs, RecommendedConfigOverrideFlags(""))
+		fs.Parse([]string{"--namespace", before})
+
+		if overrides.Context.Namespace != after {
+			t.Fatalf("Expected %s, got %s", after, overrides.Context.Namespace)
+		}
+	}
+}