| /* |
| 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 printers |
| |
| import ( |
| "encoding/base64" |
| "encoding/json" |
| "fmt" |
| "io" |
| "reflect" |
| "text/template" |
| |
| "k8s.io/apimachinery/pkg/runtime" |
| ) |
| |
| // GoTemplatePrinter is an implementation of ResourcePrinter which formats data with a Go Template. |
| type GoTemplatePrinter struct { |
| rawTemplate string |
| template *template.Template |
| } |
| |
| func NewGoTemplatePrinter(tmpl []byte) (*GoTemplatePrinter, error) { |
| t, err := template.New("output"). |
| Funcs(template.FuncMap{ |
| "exists": exists, |
| "base64decode": base64decode, |
| }). |
| Parse(string(tmpl)) |
| if err != nil { |
| return nil, err |
| } |
| return &GoTemplatePrinter{ |
| rawTemplate: string(tmpl), |
| template: t, |
| }, nil |
| } |
| |
| // AllowMissingKeys tells the template engine if missing keys are allowed. |
| func (p *GoTemplatePrinter) AllowMissingKeys(allow bool) { |
| if allow { |
| p.template.Option("missingkey=default") |
| } else { |
| p.template.Option("missingkey=error") |
| } |
| } |
| |
| // PrintObj formats the obj with the Go Template. |
| func (p *GoTemplatePrinter) PrintObj(obj runtime.Object, w io.Writer) error { |
| if InternalObjectPreventer.IsForbidden(reflect.Indirect(reflect.ValueOf(obj)).Type().PkgPath()) { |
| return fmt.Errorf(InternalObjectPrinterErr) |
| } |
| |
| var data []byte |
| var err error |
| data, err = json.Marshal(obj) |
| if err != nil { |
| return err |
| } |
| |
| out := map[string]interface{}{} |
| if err := json.Unmarshal(data, &out); err != nil { |
| return err |
| } |
| if err = p.safeExecute(w, out); err != nil { |
| // It is way easier to debug this stuff when it shows up in |
| // stdout instead of just stdin. So in addition to returning |
| // a nice error, also print useful stuff with the writer. |
| fmt.Fprintf(w, "Error executing template: %v. Printing more information for debugging the template:\n", err) |
| fmt.Fprintf(w, "\ttemplate was:\n\t\t%v\n", p.rawTemplate) |
| fmt.Fprintf(w, "\traw data was:\n\t\t%v\n", string(data)) |
| fmt.Fprintf(w, "\tobject given to template engine was:\n\t\t%+v\n\n", out) |
| return fmt.Errorf("error executing template %q: %v", p.rawTemplate, err) |
| } |
| return nil |
| } |
| |
| // safeExecute tries to execute the template, but catches panics and returns an error |
| // should the template engine panic. |
| func (p *GoTemplatePrinter) safeExecute(w io.Writer, obj interface{}) error { |
| var panicErr error |
| // Sorry for the double anonymous function. There's probably a clever way |
| // to do this that has the defer'd func setting the value to be returned, but |
| // that would be even less obvious. |
| retErr := func() error { |
| defer func() { |
| if x := recover(); x != nil { |
| panicErr = fmt.Errorf("caught panic: %+v", x) |
| } |
| }() |
| return p.template.Execute(w, obj) |
| }() |
| if panicErr != nil { |
| return panicErr |
| } |
| return retErr |
| } |
| |
| func base64decode(v string) (string, error) { |
| data, err := base64.StdEncoding.DecodeString(v) |
| if err != nil { |
| return "", fmt.Errorf("base64 decode failed: %v", err) |
| } |
| return string(data), nil |
| } |