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Simple scaffolding and code generation


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 Project Readme



Jeny is a simple yet powerful commandline tool for scaffolding new projects and generating code snippets in existing ones.

jeny --help

The outline of this readme is as follows:

  • Two use cases: scaffolding & snippets
  • The templating language
  • How do I generate dynamic file names?
  • Use --git for atomic generation of snippets
  • Configuring jeny: env vars, .jeny file and commandline options
  • Contributing, Licence, etc.

Generate a project from a scaffold

The first use case is the generation of a project structure from an existing scaffold.

jeny --[no-]edit -d ... -d ... generate path/to/scaffold path/to/target

This command will recursively copy and instantiate files and directories from the scaffold folder to the destination folder. Your favorite editor opens on files having at least one TODO.

File content is generated using a very simple and not that powerful templating language, see sections later. Code snippets of the following section are NOT supported for now.

Generate code snippets on an existing project

The second use case is the generation of code snippets inside existing annotated source code.

jeny --[no-]edit -d ... -d ... snippet snipname path/to/code

Code snippets are commented code blocks prefixed by a jeny delimiter. When executing jeny s, all files under path/to/files are inspected and jeny code blocks instantiated as uncommented code. Your favorite editor opens on files having at least one TODO.

For instance, when executing

jeny -d name:hello snippet method .

the following code block...

#jeny(method) def ${name}
#jeny(method)   # TODO
#jeny(method) end

... will generate the code below in the file where it is found, while preserving the jeny code block for subsequent calls:

def hello
  # TODO

The s[snippet] command is also able to generate fresh new files, provided they end with .jeny and have a clearly snippet identifier as first line. For instance, a file called test.rb.jeny will be instantiated when generating a method snippet if it contains the following first line:


Templating language

The current template language uses WLang with a very simple dialect. Jeny only supports simple variable for now. It does not support iterations and conditionals, on intent (?).

Let's say you specify a -d op_name:my_method commandline option, the following casing tags are recognized:

${op_name}     ->    my_method   (snake)
${opname}      ->    mymethod    (flat)
${opName}      ->    myMethod    (camel)
${OpName}      ->    MyMethod    (pascal)
${OP_NAME}     ->    MY_METHOD   (screaming)
${OP NAME}     ->    MYMETHOD    (upper)
${OPNAME}      ->    MYMETHOD    (upper flat)
${op-name}     ->    my-method   (kebab)
${Op-Name}     ->    My-Method   (header)
${OP-NAME}     ->    MY-METHOD   (cobol)
${OP|NAME}     ->    MY|METHOD   (donner)

Dynamic file names

If you need generated file name names (and/or ancestor folders), you can use the very same tags as those documented in previous section.

  • In scaffolding mode, all files can have dynamic names.
  • In snippets mode, only files with a .jeny ext can.

Atomic snippets generation

The --git commandline option (or equivalent configuration, see section below) can be used to generate snippets in an atomic way.

jeny --git -d ... s snipname

Doing so will:

  • stash any current change
  • generate code snippets
  • commit the result
  • unstash stashed changes

If anything fails, all changes are reverted before unstashing.

Please also check the --no-stash and --no-commit commandline options.

IMPORTANT You must execute jeny with a git project as current folder.

IMPORTANT Please use this option with case, as it is still experimental.

Configuration and available options

Jeny behavior can be tuned in three different ways (by ascending order of priority): environment variables, a .jeny configuration file, and command line options.

For full details, please check the documentation of Jeny::Configuration.

Environment variables

  • JENY_EDITOR, GIT_EDITOR, EDITOR are inspected in that order to find which source code editor to use

  • JENY_STATE_MANAGER=none|git is used to know which state manager to use. See Jeny::StateManager

.jeny configuration file

At start jeny looks for a .jeny configuration file in the current folder and all ancestors, and uses it to override default configuration infered from environment variables. do |c|
  # c is a Jeny::Configuration instance
  # many accessors are available for options

Commandline options

Options passed on the commandline always override the configuration obtained through environment variables and the .jeny file.

For a full list of options, check the help:

jeny --help

Public API

This library uses SemVer 2.0. Its public API is:

  • The command line tool and its options
  • The Configuration class powering the .jeny file
  • All recognized environment variables and their effect on configuration
  • The syntax and semantics of #jeny blocks and file header
  • The syntax and semantics of the templating language


Use github issues and pull requests for contributions. Please favor pull requests if possible for small changes. Make sure to keep in touch with us before making big changes though, as they might not be aligned with our roadmap, or conflict with open pull requests.


This software is distributed by Enspirit SRL under a MIT Licence. Please contact Bernard Lambeau ( with any question.