github.com/containerd/nerdctl/v2@v2.0.0-beta.5.0.20240520001846-b5758f54fa28/pkg/formatter/common.go (about) 1 /* 2 Copyright The containerd Authors. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package formatter 18 19 import ( 20 "bytes" 21 "encoding/json" 22 "errors" 23 "fmt" 24 "io" 25 "text/template" 26 27 "github.com/docker/cli/templates" 28 ) 29 30 // Flusher is implemented by text/tabwriter.Writer 31 type Flusher interface { 32 Flush() error 33 } 34 35 // FormatSlice formats the slice with `--format` flag. 36 // 37 // --format="" (default): JSON 38 // --format='{{json .}}': JSON lines 39 // 40 // FormatSlice is expected to be only used for `nerdctl OBJECT inspect` commands. 41 func FormatSlice(format string, writer io.Writer, x []interface{}) error { 42 var tmpl *template.Template 43 switch format { 44 case "": 45 b, err := json.MarshalIndent(x, "", " ") 46 if err != nil { 47 return err 48 } 49 fmt.Fprintln(writer, string(b)) 50 case "raw", "table", "wide": 51 return errors.New("unsupported format: \"raw\", \"table\", and \"wide\"") 52 default: 53 var err error 54 tmpl, err = ParseTemplate(format) 55 if err != nil { 56 return err 57 } 58 for _, f := range x { 59 var b bytes.Buffer 60 if err := tmpl.Execute(&b, f); err != nil { 61 if _, ok := err.(template.ExecError); ok { 62 // FallBack to Raw Format 63 if err = tryRawFormat(&b, f, tmpl); err != nil { 64 return err 65 } 66 } 67 } 68 if _, err = fmt.Fprintln(writer, b.String()); err != nil { 69 return err 70 } 71 } 72 } 73 return nil 74 } 75 76 func tryRawFormat(b *bytes.Buffer, f interface{}, tmpl *template.Template) error { 77 m, err := json.MarshalIndent(f, "", " ") 78 if err != nil { 79 return err 80 } 81 82 var raw interface{} 83 rdr := bytes.NewReader(m) 84 dec := json.NewDecoder(rdr) 85 dec.UseNumber() 86 87 if rawErr := dec.Decode(&raw); rawErr != nil { 88 return fmt.Errorf("unable to read inspect data: %v", rawErr) 89 } 90 91 tmplMissingKey := tmpl.Option("missingkey=error") 92 if rawErr := tmplMissingKey.Execute(b, raw); rawErr != nil { 93 return fmt.Errorf("template parsing error: %v", rawErr) 94 } 95 96 return nil 97 } 98 99 // ParseTemplate wraps github.com/docker/cli/templates.Parse() to allow `json` as an alias of `{{json .}}`. 100 // ParseTemplate can be removed when https://github.com/docker/cli/pull/3355 gets merged and tagged (Docker 22.XX). 101 func ParseTemplate(format string) (*template.Template, error) { 102 aliases := map[string]string{ 103 "json": "{{json .}}", 104 } 105 if alias, ok := aliases[format]; ok { 106 format = alias 107 } 108 return templates.Parse(format) 109 }