kubernetes/pkg/kubectl/explain/explain.go
Kubernetes Submit Queue 761fdeacaa
Merge pull request #55689 from luksa/kubectl_explain_kind_version
Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Make kubectl explain print the Kind and APIVersion of the resource

**What this PR does / why we need it**:
Kubectl explain currently doesn't print out the Kind and APIversion of the resource being explained. When running `kubectl explain hpa.spec`, for example, there is no way of knowing whether you're looking at the `autoscaling/v1` or the `autoscaling/v2beta1` version. 
Also, `kubectl explain` is often used as a reference when writing YAML/JSON object manifests. It allows you to look up everything except the API version. Currently, you either need to know the API Version of a resource by heart or look it up in the online API docs. 
This PR fixes both problems by having `kubectl explain` print out the full Kind and APIVersion of the resource it is explaining.

Here are a few examples of the new output:
```
$ kubectl explain deploy
KIND:     Deployment
VERSION:  extensions/v1beta1

DESCRIPTION:
...


$ kubectl explain hpa.spec
KIND:     HorizontalPodAutoscaler
VERSION:  autoscaling/v1

RESOURCE: spec <Object>

DESCRIPTION:
...


$ kubectl explain hpa.spec.maxReplicas
KIND:     HorizontalPodAutoscaler
VERSION:  autoscaling/v1

FIELD:    maxReplicas <integer>

DESCRIPTION:
...


$ kubectl explain hpa.spec --recursive
KIND:     HorizontalPodAutoscaler
VERSION:  autoscaling/v1

RESOURCE: spec <Object>

DESCRIPTION:
     behaviour of autoscaler. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status.

     specification of a horizontal pod autoscaler.

FIELDS:
   maxReplicas	<integer>
   minReplicas	<integer>
   scaleTargetRef	<Object>
      apiVersion	<string>
      kind	<string>
      name	<string>
   targetCPUUtilizationPercentage	<integer>
```

**Release note**:

```release-note
Kubectl explain now prints out the Kind and API version of the resource being explained
```
2017-12-15 08:12:28 -08:00

70 lines
2.1 KiB
Go

/*
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 explain
import (
"io"
"strings"
"k8s.io/apimachinery/pkg/api/meta"
"k8s.io/apimachinery/pkg/runtime/schema"
"k8s.io/kube-openapi/pkg/util/proto"
)
type fieldsPrinter interface {
PrintFields(proto.Schema) error
}
func splitDotNotation(model string) (string, []string) {
var fieldsPath []string
// ignore trailing period
model = strings.TrimSuffix(model, ".")
dotModel := strings.Split(model, ".")
if len(dotModel) >= 1 {
fieldsPath = dotModel[1:]
}
return dotModel[0], fieldsPath
}
// SplitAndParseResourceRequest separates the users input into a model and fields
func SplitAndParseResourceRequest(inResource string, mapper meta.RESTMapper) (string, []string, error) {
inResource, fieldsPath := splitDotNotation(inResource)
inResource, _ = mapper.ResourceSingularizer(inResource)
return inResource, fieldsPath, nil
}
// PrintModelDescription prints the description of a specific model or dot path.
// If recursive, all components nested within the fields of the schema will be
// printed.
func PrintModelDescription(fieldsPath []string, w io.Writer, schema proto.Schema, gvk schema.GroupVersionKind, recursive bool) error {
fieldName := ""
if len(fieldsPath) != 0 {
fieldName = fieldsPath[len(fieldsPath)-1]
}
// Go down the fieldsPath to find what we're trying to explain
schema, err := LookupSchemaForField(schema, fieldsPath)
if err != nil {
return err
}
b := fieldsPrinterBuilder{Recursive: recursive}
f := &Formatter{Writer: w, Wrap: 80}
return PrintModel(fieldName, f, b, schema, gvk)
}