tagfmt

Tagfmt formats struct tag within Go programs.

It uses blanks for alignment. tag must be in key:"value" pair format

tagfmt feature:

• align field tags in part
• fill specified tag key to field
• sort field tags

get tagfmt

you can download from github releases

https://github.com/bigpigeon/tagfmt/releases

or go get

go get github.com/bigpigeon/tagfmt

usage

usage: tagfmt [flags] [path ...]
  -P string
        field name with inverse regular expression pattern
  -a    align with nearby field's tag (default true)
  -cpuprofile string
        write cpu profile to this file
  -d    display diffs instead of rewriting files
  -e    report all errors (not just the first 10 on different lines)
  -f string
        fill key and value for field e.g json=lower(_val)|yaml=snake(_val)
  -l    list files whose formatting differs from tagfmt's
  -p string
        field name with regular expression pattern (default ".*")
  -s    sort struct tag by key
  -sP string
        struct name with inverse regular expression pattern
  -so string
        sort struct tag keys order e.g json|yaml|desc
  -sp string
        struct name with regular expression pattern (default ".*")
  -sw string
        sort struct tag keys weight e.g json=1|yaml=2|desc=-1 the higher weight, the higher the ranking, default keys weight is 0
  -w    write result to (source) file instead of stdout

use in vscode

1. install filewatcher extension first
2. edit filewatcher settings
3. add sub item to filewatcher.commands, and then save it
4. open the go file, add struct field and then save it

{
   "match": "\\.go",
   "isAsync": true,
   "event": "onFileChange",
   "cmd": "tagfmt -w -f \"json=or(:tag,snake(:field))|yaml=or(:tag,lower_camel(:field))\" ${file} -s -so \"json|yaml\" ${file} " 
}

tag align

align tag according to the longest tag's object of each column

// tagfmt .
package main
type Example struct {
	Data      string `xml:"data" yaml:"data"  json:"data"`
	OtherData string `xml:"other_data" json:"other_data:omitempty" yaml:"other_data"`
}

the result

// tagfmt 
package main

type Example struct {
	Data      string `xml:"data"       yaml:"data"                 json:"data"`
	OtherData string `xml:"other_data" json:"other_data:omitempty" yaml:"other_data"`
}

space line or no tag's field will split this rule, just like struct field align by gofmt

//tagfmt
package main
type Example struct {
	Data string `xml:"data" yaml:"data,omitempty"  json:"data"`
	OtherData string `xml:"other_data" json:"other_data" yaml:"other_data"`

    NewLineData string `xml:"new_line_data" yaml:"new_line_data" json:"new_line_data"`
    NewLineOtherData string `xml:"new_line_other_data" yaml:"new_line_other_data"  json:"new_line_other_data"`
}
// after format
package main

type Example struct {
	Data      string `xml:"data"       yaml:"data,omitempty" json:"data"`
	OtherData string `xml:"other_data" json:"other_data"     yaml:"other_data"`

	NewLineData      string `xml:"new_line_data"       yaml:"new_line_data"       json:"new_line_data"`
	NewLineOtherData string `xml:"new_line_other_data" yaml:"new_line_other_data" json:"new_line_other_data"`
}

tag fill

tag fill can fill specified key to field tag

e.g

//tagfmt -f "json=:field"

type OrderDetail struct {
	ID       string   ``
	UserName string   `json:"name"`
	OrderID  string   `json:"order"`
	Callback string   ``
	Address  []string ``
}
// after format
package main

type OrderDetail struct {
	ID       string   `json:"ID"`
	UserName string   `json:"name"`
	OrderID  string   `json:"order"`
	Callback string   `json:"callback"`
	Address  []string `json:"address"`
}

if you didn't want to change the existing tag, use 'or' function

//tagfmt -f "json=or(:tag, :field)"

type OrderDetail struct {
	ID       string   ``
	UserName string   `json:"name"`
	OrderID  string   `json:"order"`
	Callback string   ``
	Address  []string ``
}
// after format
package main

type OrderDetail struct {
	ID       string   `json:"ID"`
	UserName string   `json:"name"`
	OrderID  string   `json:"order"`
	Callback string   `json:"Callback"`
	Address  []string `json:"Address"`
}

and then I hope the tag convert to snake case style, use snake

//tagfmt -f "json=or(:tag, snake(:field))"
type OrderDetail struct {
	ID       string   ``
	UserName string   `json:"name"`
	OrderID  string   `json:"order"`
	Callback string   ``
	Address  []string ``
}
// after format
package main

type OrderDetail struct {
	ID       string   `json:"id"`
	UserName string   `json:"name"`
	OrderID  string   `json:"order"`
	Callback string   `json:"callback"`
	Address  []string `json:"address"`
}

final my struct tag have some extra data need to keep it is, use ':tag_extra' to get extra data and '+' to link it

//tagfmt -f "json=snake(:field)+':tag_extra'"
type OrderDetail struct {
	ID       string   ``
	UserName string   `json:",omitempty"`
	OrderID  string   `json:"order,omitempty"`
	Callback string   ``
	Address  []string ``
}
// after format
package main

type OrderDetail struct {
	ID       string   `json:"id"`
	UserName string   `json:"user_name,omitempty"`
	OrderID  string   `json:"order_id,omitempty"`
	Callback string   `json:"callback"`
	Address  []string `json:"address"`
}

fill rule have many functions and placeholders to avoid writing tags manually

tag fill with comment filter

use // tagfill: [key1 key2] to filter below struct requires key

//tagfmt -f "json=snake(:tag)|yaml=lower_camel(:tag)|bson=lower_camel(:tag)|toml=upper_camel(:tag)"

package main
// tagfill: toml yaml
type OrderConfig struct {
	Name     string ``
    UserName string ``
    Pay      int    ``
}
// tagfill: json bson
type OrderDetail struct {
    ID       string ``
    UserName string ``
    Pay      int    ``
}

after format

//tagfmt -f "json=snake(:tag)|yaml=lower_camel(:tag)|bson=lower_camel(:tag)|toml=upper_camel(:tag)"

package main

// tagfill: toml yaml
type OrderConfig struct {
	Name     string `toml:"" yaml:""`
	UserName string `toml:"" yaml:""`
	Pay      int    `toml:"" yaml:""`
}

// tagfill: json bson
type OrderDetail struct {
	ID       string `bson:"" json:""`
	UserName string `bson:"" json:""`
	Pay      int    `bson:"" json:""`
}

tag sort

//tagfmt -s
package main
type Example struct {
	Data string `xml:"data" yaml:"data"  json:"data"  `
}
// after format
package main

type Example struct {
	Data string `json:"data" xml:"data" yaml:"data"`
}

you can use tag sort order to custom sort order

//tagfmt -s -so "json|yaml|desc"
package main
type Example struct {
	Data string `desc:"some inuse data" yaml:"data" json:"data" `
}
// after format
package main

type Example struct {
	Data string `json:"data" yaml:"data" desc:"some inuse data"`
}

use sort weight to determine the sort order

//tagfmt -s -sw "json=2|yaml=1|toml=1|desc=-1"
package main
type Example struct {
	Data string `desc:"some inuse data" yaml:"data" toml:"data" binding:"required" json:"data" `
}
// after format
package main

type Example struct {
	Data string `json:"data" toml:"data" yaml:"data" binding:"required" desc:"some inuse data"`
}

tag select

when use -p "regex" the tagfmt only select fields that match the regular expression

you also use the -P "regex" to invert the select

//tagfmt -P "^Ignore.*$"
type OrderDetail struct {
	ID       string   `json:"id" yaml:"id"`
	UserName string   `json:"user_name" yaml:"user_name"`
	Ignore   string   `json:"-" yaml:"-"`
	OrderID  string   `json:"order_id" yaml:"order_id"`
	Callback string   `json:"callback" yaml:"callback"`
	Address  []string `json:"address" yaml:"address"`
}

type OrderDetail struct {
	ID       string   `json:"id"        yaml:"id"`
	UserName string   `json:"user_name" yaml:"user_name"`
	Ignore   string   `json:"-" yaml:"-"`
	OrderID  string   `json:"order_id" yaml:"order_id"`
	Callback string   `json:"callback" yaml:"callback"`
	Address  []string `json:"address"  yaml:"address"`
}

struct select

just like tag select, use -sp "regex" regular expression to match what struct you want

use the -sP "regex" to invert the select