gomodifytags

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1 StructTag

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package main

import (
  "fmt"
  "reflect"
)

func main() {
  tag := reflect.StructTag(`species:"gopher" color:"blue"`)
  fmt.Println(tag.Get("color"), tag.Get("species"))
}
blue gopher

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package main

import (
  "fmt"

  "github.com/fatih/structtag"
)

func main() {
  tag := `json:"foo,omitempty,string" xml:"foo"`

  // parse the tag
  tags, err := structtag.Parse(string(tag))
  if err != nil {
    panic(err)
  }

  // iterate over all tags
  for _, t := range tags.Tags() {
    fmt.Printf("tag: %+v\n", t)
  }

  // get a single tag
  jsonTag, err := tags.Get("json")
  if err != nil {
    panic(err)
  }

  // change existing tag
  jsonTag.Name = "foo_bar"
  jsonTag.Options = nil
  tags.Set(jsonTag)

  // add new tag
  tags.Set(&structtag.Tag{
    Key:     "hcl",
    Name:    "foo",
    Options: []string{"squash"},
  })

  // print the tags
  fmt.Println(tags) // Output: json:"foo_bar" xml:"foo" hcl:"foo,squash"
}
tag: json:"foo,omitempty,string"
tag: xml:"foo"
json:"foo_bar" xml:"foo" hcl:"foo,squash"

2 AST(抽象语法树)

遍历语法树，展示结构体字段列表： 

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package main

import (
  "fmt"
  "go/ast"
  "go/parser"
  "go/token"
)

func main() {
  src := `package main
	type Example struct {
    Foo string` + " `json:\"foo\"` }"

  fset := token.NewFileSet()
  file, err := parser.ParseFile(fset, "demo", src, parser.ParseComments)
  if err != nil {
    panic(err)
  }

  ast.Inspect(file, func(x ast.Node) bool {
    s, ok := x.(*ast.StructType)
    if !ok {
      return true
    }

    for _, field := range s.Fields.List {
      fmt.Printf("Field: %s\n", field.Names[0].Name)
      fmt.Printf("Tag:   %s\n", field.Tag.Value)
    }
    return false
  })
}
Field: Foo
Tag:   `json:"foo"`

3 gomodifytags

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package main

type Server struct {
  Name        string
  Port        int
  EnableLogs  bool
  BaseDomain  string
  Credentials struct {
    Username string
    Password string
  }
}

3.1 Struct based modification

gomodifytags -file demo.go -struct Server -add-tags json -w
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package main

type Server struct {
  Name        string `json:"name"`
  Port        int    `json:"port"`
  EnableLogs  bool   `json:"enable_logs"`
  BaseDomain  string `json:"base_domain"`
  Credentials struct {
    Username string `json:"username"`
    Password string `json:"password"`
  } `json:"credentials"`
}

支持三种 transform , 如下所示：

  • snakecase: “BaseDomain” -> “base_domain”
  • camelcase: “BaseDomain” -> “baseDomain”
  • lispcase: “BaseDomain” -> “base-domain” 
gomodifytags -file demo.go -struct Server -add-tags xml -transform camelcase
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package main

type Server struct {
  Name        string `json:"name" xml:"name"`
  Port        int    `json:"port" xml:"port"`
  EnableLogs  bool   `json:"enable_logs" xml:"enableLogs"`
  BaseDomain  string `json:"base_domain" xml:"baseDomain"`
  Credentials struct {
    Username string `json:"username" xml:"username"`
    Password string `json:"password" xml:"password"`
  } `json:"credentials" xml:"credentials"`
}
gomodifytags -file demo.go -struct Server -add-tags xml -transform camelcase
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package main

type Server struct {
  Name        string `json:"name" xml:"name"`
  Port        int    `json:"port" xml:"port"`
  EnableLogs  bool   `json:"enable_logs" xml:"enableLogs"`
  BaseDomain  string `json:"base_domain" xml:"baseDomain"`
  Credentials struct {
    Username string `json:"username" xml:"username"`
    Password string `json:"password" xml:"password"`
  } `json:"credentials" xml:"credentials"`
}
gomodifytags -file demo.go -struct Server -add-tags validate:gt=1,scope:read-only
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package main

type Server struct {
  Name        string `json:"name" validate:"gt=1" scope:"read-only"`
  Port        int    `json:"port" validate:"gt=1" scope:"read-only"`
  EnableLogs  bool   `json:"enable_logs" validate:"gt=1" scope:"read-only"`
  BaseDomain  string `json:"base_domain" validate:"gt=1" scope:"read-only"`
  Credentials struct {
    Username string `json:"username" validate:"gt=1" scope:"read-only"`
    Password string `json:"password" validate:"gt=1" scope:"read-only"`
  } `json:"credentials" validate:"gt=1" scope:"read-only"`
}
gomodifytags -file demo.go -struct Server -add-tags json --add-options json=omitempty -w
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package main

type Server struct {
  Name        string `json:"name,omitempty"`
  Port        int    `json:"port,omitempty"`
  EnableLogs  bool   `json:"enable_logs,omitempty"`
  BaseDomain  string `json:"base_domain,omitempty"`
  Credentials struct {
    Username string `json:"username,omitempty"`
    Password string `json:"password,omitempty"`
  } `json:"credentials,omitempty"`
}
gomodifytags -file demo.go -struct Server -remove-tags json
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package main

type Server struct {
  Name        string
  Port        int
  EnableLogs  bool
  BaseDomain  string
  Credentials struct {
    Username string
    Password string
  }
}
gomodifytags -file demo.go -struct Server -clear-tags
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package main

type Server struct {
  Name        string
  Port        int
  EnableLogs  bool
  BaseDomain  string
  Credentials struct {
    Username string
    Password string
  }
}
gomodifytags -file demo.go -struct Server -remove-options json=omitempty
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package main

type Server struct {
  Name        string `json:"name"`
  Port        int    `json:"port"`
  EnableLogs  bool   `json:"enable_logs"`
  BaseDomain  string `json:"base_domain"`
  Credentials struct {
    Username string `json:"username"`
    Password string `json:"password"`
  } `json:"credentials"`
}
gomodifytags -file demo.go -struct Server -clear-options
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package main

type Server struct {
  Name        string `json:"name"`
  Port        int    `json:"port"`
  EnableLogs  bool   `json:"enable_logs"`
  BaseDomain  string `json:"base_domain"`
  Credentials struct {
    Username string `json:"username"`
    Password string `json:"password"`
  } `json:"credentials"`
}

3.2 Line based modification

gomodifytags -file demo.go -line 8,11 -clear-tags json
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package main

type Server struct {
  Name        string `json:"name,omitempty"`
  Port        int    `json:"port,omitempty"`
  EnableLogs  bool   `json:"enable_logs,omitempty"`
  BaseDomain  string `json:"base_domain,omitempty"`
  Credentials struct {
    Username string
    Password string
  }
}
gomodifytags -file demo.go -line 6,7 -remove-tags json
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package main

type Server struct {
  Name        string `json:"name,omitempty"`
  Port        int    `json:"port,omitempty"`
  EnableLogs  bool
  BaseDomain  string
  Credentials struct {
    Username string `json:"username,omitempty"`
    Password string `json:"password,omitempty"`
  } `json:"credentials,omitempty"`
}
gomodifytags -file demo.go -line 2,7 -add-tags bson
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package main

type Server struct {
  Name        string `json:"name,omitempty" bson:"name"`
  Port        int    `json:"port,omitempty" bson:"port"`
  EnableLogs  bool   `json:"enable_logs,omitempty" bson:"enable_logs"`
  BaseDomain  string `json:"base_domain,omitempty" bson:"base_domain"`
  Credentials struct {
    Username string `json:"username,omitempty"`
    Password string `json:"password,omitempty"`
  } `json:"credentials,omitempty"`
}
gomodifytags -file demo.go -offset 100 -add-tags bson
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package main

type Server struct {
  Name        string `json:"name,omitempty" bson:"name"`
  Port        int    `json:"port,omitempty" bson:"port"`
  EnableLogs  bool   `json:"enable_logs,omitempty" bson:"enable_logs"`
  BaseDomain  string `json:"base_domain,omitempty" bson:"base_domain"`
  Credentials struct {
    Username string `json:"username,omitempty" bson:"username"`
    Password string `json:"password,omitempty" bson:"password"`
  } `json:"credentials,omitempty" bson:"credentials"`
}

3.3 Shortcoming

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package main

type User struct {
  First_name string
  Last_name  string
  addr       string
}
gomodifytags -file user.go -struct User -add-tags json

期望得到的结果是： first_name ,但是却得到了 first___name, 同时 addr 字段不导出也生成了 tag, 如下所示： 

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package main

type User struct {
  First_name string `json:"first___name"`
  Last_name  string `json:"last___name"`
  addr       string `json:"addr"`
}
Last Updated 2017-11-09 Thu 15:00.
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