Featuregen

Simple code generation without Python, Node.js, or external dependencies.

Featuregen is a tiny, dependency-free code generator written in POSIX shell.

It transforms template files into one or more source files using a small, purpose-built template language.

Need help creating a template? Use the optional AI-powered Telegram assistant to generate a starting point.

The repository contains the Featuregen engine itself (implemented as a POSIX shell script) together with a comprehensive automated test suite written in Kotlin and JUnit, making the project easy to verify and extend.

Features

• Zero dependencies
• POSIX shell compatible
• Multiple output files from a single template
• Built-in string transformation functions
• Simple and readable template language

---

Example

Template:

@expect package
@expect fullName

@let shortName = extractIgnoringCase(fullName, Feature)
@let snakeCaseName = snake(fullName)
@let packagePath = pathFromPackage(package)

@file path=~<<packagePath>>/~<<snakeCaseName>>/di/~<<shortName>>Module.kt
@@fstart
package ~<<package>>.~<<snakeCaseName>>.di

import ~<<package>>.~<<snakeCaseName>>.presentation.~<<shortName>>ViewModel

val ~<<shortName>>Module = module {

    viewModelOf(::~<<shortName>>ViewModel)
}
@@fend

Run:

./featuregen template.featuregen \
    package=foo.bar \
    fullName=FeatureLogin

Generated file:

foo/bar/feature_login/di/LoginModule.kt

Contents:

package foo.bar.feature_login.di

import foo.bar.feature_login.presentation.LoginViewModel

val LoginModule = module {

    viewModelOf(::LoginViewModel)
}

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Template Language

@expect

Requires a variable to be provided.

@expect package

Variables are passed as command-line arguments.

name=FeatureLogin
package=com.example.demo

Reference them using

~<<name>>

Generation fails if the variable is missing.

---

@let

Creates a new variable from a built-in function.

@let packagePath = pathFromPackage(package)

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@file

Defines the destination file.

@file path=src/~<<packagePath>>/Login.kt

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File Blocks

Everything between @@fstart and @@fend becomes the contents of a generated file.

@@fstart
Hello
@@fend

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Built-in Functions

Function	Description
camel(value)	Converts text to camelCase
snake(value)	Converts text to snake_case
screamingSnake(value)	Converts text to SCREAMING_SNAKE_CASE
pathFromPackage(value)	Converts com.example.app → com/example/app
extractIgnoringCase(value, remove)	Removes a substring ignoring case
featuregenVersion()	Returns the current Featuregen version

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Comments

Lines starting with // outside file blocks are treated as comments and ignored by the generator.

// This is a comment

@expect package

@file path=src/~<<packagePath>>/Example.kt

@@fstart
// This comment will be written to the generated file.
@@fend

Inside @@fstart and @@fend, every line—including those starting with //—is treated as file content.

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Template Assistant

FeatureGen includes an optional AI-powered Telegram assistant that helps you create .featuregen templates by describing the files and structure you want to generate.

Describe what you want to build, or provide a code snippet, and the bot will help you create the corresponding template.

Useful for:

• bootstrapping a ready-to-run Featuregen setup (script + template)
• creating new templates

➡️ Use the bot here: @featuregen_bot

Note: The bot is an external tool and is not required to use FeatureGen.

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License

MIT License