8442a118ea
This fixes #38779. This allows us to avoid case in which printers.GetStandardPrinter returns nil for both printer and err removing any potential panics that may arise throughout kubectl commands. Please see #38779 and #38112 for complete context. Add comment explaining adding handlers to printers.HumanReadablePrinter also remove an unnecessary conversion of printers.HumanReadablePrinter to printers.ResourcePrinter.
115 lines
3.2 KiB
Go
115 lines
3.2 KiB
Go
/*
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Copyright 2017 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package printers
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import (
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"encoding/json"
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"fmt"
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"io"
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"text/template"
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"k8s.io/apimachinery/pkg/runtime"
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)
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// TemplatePrinter is an implementation of ResourcePrinter which formats data with a Go Template.
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type TemplatePrinter struct {
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rawTemplate string
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template *template.Template
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}
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func NewTemplatePrinter(tmpl []byte) (*TemplatePrinter, error) {
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t, err := template.New("output").
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Funcs(template.FuncMap{"exists": exists}).
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Parse(string(tmpl))
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if err != nil {
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return nil, err
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}
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return &TemplatePrinter{
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rawTemplate: string(tmpl),
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template: t,
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}, nil
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}
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// AllowMissingKeys tells the template engine if missing keys are allowed.
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func (p *TemplatePrinter) AllowMissingKeys(allow bool) {
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if allow {
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p.template.Option("missingkey=default")
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} else {
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p.template.Option("missingkey=error")
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}
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}
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func (p *TemplatePrinter) AfterPrint(w io.Writer, res string) error {
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return nil
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}
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// PrintObj formats the obj with the Go Template.
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func (p *TemplatePrinter) PrintObj(obj runtime.Object, w io.Writer) error {
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var data []byte
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var err error
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data, err = json.Marshal(obj)
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if err != nil {
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return err
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}
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out := map[string]interface{}{}
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if err := json.Unmarshal(data, &out); err != nil {
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return err
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}
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if err = p.safeExecute(w, out); err != nil {
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// It is way easier to debug this stuff when it shows up in
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// stdout instead of just stdin. So in addition to returning
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// a nice error, also print useful stuff with the writer.
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fmt.Fprintf(w, "Error executing template: %v. Printing more information for debugging the template:\n", err)
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fmt.Fprintf(w, "\ttemplate was:\n\t\t%v\n", p.rawTemplate)
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fmt.Fprintf(w, "\traw data was:\n\t\t%v\n", string(data))
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fmt.Fprintf(w, "\tobject given to template engine was:\n\t\t%+v\n\n", out)
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return fmt.Errorf("error executing template %q: %v", p.rawTemplate, err)
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}
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return nil
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}
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// TODO: implement HandledResources()
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func (p *TemplatePrinter) HandledResources() []string {
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return []string{}
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}
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func (p *TemplatePrinter) IsGeneric() bool {
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return true
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}
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// safeExecute tries to execute the template, but catches panics and returns an error
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// should the template engine panic.
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func (p *TemplatePrinter) safeExecute(w io.Writer, obj interface{}) error {
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var panicErr error
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// Sorry for the double anonymous function. There's probably a clever way
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// to do this that has the defer'd func setting the value to be returned, but
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// that would be even less obvious.
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retErr := func() error {
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defer func() {
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if x := recover(); x != nil {
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panicErr = fmt.Errorf("caught panic: %+v", x)
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}
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}()
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return p.template.Execute(w, obj)
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}()
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if panicErr != nil {
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return panicErr
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}
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return retErr
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}
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