tojen

tojen

tojen is a code generator that generates jennifer code from a existing file.

Why?

Well writing code that generates code is tedious. This tool removes some of the tedium by setting up a base that can be changed and extended to suit your needs for code generation.

This was mostly inspired by the functionality of the go text/template system. The advantage is that static code was easy to write, but dynamic typesafe code was a big challenge. Also as the project grew the templates would get harder and harder to read.

I created this project to further bridge the gap between the advantages of the text/template and keeping all the generation in the go language with jennifer.

How?

The command line is all you need.

go install github.com/aloder/tojen

In your terminal

tojen gen [source file]

This just takes the sourcefile and outputs the code in the terminal.

tojen gen [source file] [output file]

This takes the source file and outputs the code in the specified file

Examples

Hello World

File main.go is defined as:

package main

import "fmt"

func main() {
        fmt.Println("Hello World!")
}

Running command:

tojen gen main.go

Will print out:

package main

import jen "github.com/dave/jennifer/jen"

func genDeclAt15() jen.Code {
        return jen.Null()
}
func genFuncmain() jen.Code {
        return jen.Func().Id("main").Params().Block(jen.Qual("fmt", "Println").Call(jen.Lit("Hello World!")))
}
func genFile() *jen.File {
        ret := jen.NewFile("main")
        ret.Add(genDeclAt15())
        ret.Add(genFuncmain())
        return ret
}

It print out to the console because there was no secondary argument. This is useful for writing out simple end results that you would like jennifer to write then copying them into your code. If you would like to save the file, set the second argument.

Static Struct

Say you want to generate a static struct.

package model

type User struct {
  Name     string
  Email    string
  Password string
}

Running the command

tojen gen [path to user file] [output file]

Generates this

package main

import jen "github.com/dave/jennifer/jen"

func genDeclAt16() jen.Code {
	return jen.Null().Type().Id("User").Struct(
		jen.Id("Name").Id("string"),
		jen.Id("Email").Id("string"),
		jen.Id("Password").Id("string"))
}
func genFile() *jen.File {
	ret := jen.NewFile("model")
	ret.Add(genDeclAt16())
	return ret
}

The Idea of this package is not to generate and forget but rather to establish a boilerplate that allows you to extend and modify.

If I only wanted the user struct code I would modify it to this:

func genUserStruct() jen.Code {
	return jen.Type().Id("User").Struct(
		jen.Id("Name").Id("string"),
		jen.Id("Email").Id("string"),
		jen.Id("Password").Id("string"))
}

Now we have usable generation of static code that can be used in a project using jennifer.

Notes

Feel free to create an issue if you are having a problem or have a feature request. Pull requests are welcome as well.