flora

README

Flora

Compile-time Dependency Injection for Go.
Spring-like convenience, zero runtime overhead, and absolutely no magic.

Why Flora?

Dependency Injection in Go traditionally forces developers to choose between two painful extremes:

1. Manual Wiring (Boilerplate): You manually construct the dependency graph or maintain massive ProviderSets (e.g., in Google Wire). As your application scales to dozens of services, wiring becomes a tedious, unmaintainable chore.
2. Reflection (Runtime Magic): You use dynamic frameworks that resolve dependencies at runtime. This causes slower startup times, circumvents Go's strict compiler, and worst of all: missing dependencies cause your application to panic at runtime instead of failing during compilation.

Flora solves this by acting as a "Convention over Configuration" layer. It parses your source code's Abstract Syntax Tree (AST) to natively discover your components, and then automatically generates a strongly-typed DI container using Google Wire under the hood.

You get the developer experience of a modern, automated framework with the safety and performance of purely static code.

• Zero Runtime Overhead: The generated container is exactly as fast and memory-efficient as manually written Go code.
• No Reflection: Everything is evaluated at compile-time. If your code compiles, your dependency graph is 100% safe.
• Auto-Discovery: Just embed a marker into your structs. Flora reads your constructors and wires the entire graph automatically.
• Native Go Idioms: Full, automatic support for constructors returning initialization errors and cleanup func() routines for graceful shutdowns.

---

Installation

Flora consists of a CLI tool (to generate the container) and a core library (for the markers).

# 1. Install the CLI tool globally
go install github.com/soner3/flora/cmd/flora@latest

# 2. Add the library to your project
go get github.com/soner3/flora@latest

---

Quick Start

Instead of maintaining huge initialization scripts, you define dependencies declaratively right where they belong.

package main

import "github.com/soner3/flora"

// 1. Mark your struct as a component
type Greeter struct {
    flora.Component
}

// 2. Provide a standard constructor
func NewGreeter() *Greeter {
    return &Greeter{}
}

func (g *Greeter) Greet() string { return "Hello from Flora!" }

type App struct {
    flora.Component
    greeter *Greeter
}

// Flora automatically discovers the *Greeter dependency and injects it.
func NewApp(g *Greeter) *App {
    return &App{greeter: g}
}

Generate the container by running the CLI in your project root:

flora gen -i . -o .

---

Core Concepts & Reference

Flora uses two primary markers to understand your architecture. Knowing when to use which is the key to building clean applications.

1. flora.Component (For your Domain Logic)

Use this for structs that you own and write yourself (e.g., Services, Handlers, Repositories). By embedding flora.Component, you tell Flora to manage this struct.

Default Behaviors:

• Constructor: Flora automatically looks for an exported function named New<StructName> (e.g., NewUserService).
• Scope: singleton (one instance per application container).
• Interfaces: If the struct implements any interfaces, Flora binds them automatically.

Tag Reference: You can override the default behavior using the flora struct tag. Multiple tags can be combined using commas.

Tag	Example	Description
(Shorthand)	flora:"BuildApp"	Any string without a key-value pair is automatically treated as the constructor name.
constructor	flora:"constructor=BuildApp"	Explicitly overrides the default New<StructName> constructor lookup.
primary	flora:"primary"	Resolves interface collisions. If multiple structs implement the same interface, the primary one is injected.
scope	flora:"scope=prototype"	Changes the lifecycle to a Factory function (a fresh instance is created per injection).
order	flora:"order=1"	Defines the sorting order when the component is injected via Slice ([]Interface).
(Empty)	flora:""	Explicitly marks a component with default rules (optional, embedding the struct is usually enough).

2. flora.Configuration (For Third-Party & Adapters)

Use this when you cannot (or should not) modify the target struct. This is strictly meant for Third-Party Integrations (like *sql.DB, *redis.Client) or functional paradigms (like pure HTTP Middlewares).

Instead of embedding a marker into the target struct, you create a config struct and use Magic Comments (// flora:...) above its provider methods.

package config

import (
    "database/sql"
    "github.com/soner3/flora"
)

type DatabaseConfig struct {
    flora.Configuration
}

// flora:primary
func (c *DatabaseConfig) ProvidePostgres() (*sql.DB, func(), error) {
    db, err := sql.Open("postgres", "...")
    if err != nil {
      return nil, nil, err
    }
    
    // Flora handles the cleanup function automatically during graceful shutdown!
    cleanup := func() { db.Close() }
    
    return db, cleanup, nil 
}

Magic Comment Reference: Because Go does not allow struct tags on functions, Flora reads the comments immediately preceding the provider method.

Comment	Description
// flora:primary	Marks the returned type as the primary implementation.
// flora:scope=prototype	Changes the lifecycle to a Factory function.
// flora:order=1	Defines the sorting order when injected via Slice ([]Interface).

---

Advanced Usage

Clean Architecture & Type Aliasing

In Hexagonal or Clean Architecture, your core domain should not have direct dependencies on external frameworks ("Framework Pollution"). Flora fully supports Go Type Aliases (=) to keep your domain pure.

package domain

import "github.com/soner3/flora"

// 1. Define a neutral alias in your domain layer
type DIComponent = flora.Component

// 2. Use the alias in your domain structs. No direct framework imports!
type UserService struct {
    DIComponent `flora:"primary"`
    repo UserRepository
}

Multi-Binding (Slice Injection)

Building extensible systems usually requires tedious array wiring. With Flora, you simply define an interface, implement it multiple times, and request a slice []YourInterface. Flora handles the aggregation and sorting based on the order tag.

// flora:order=1
func (c *MiddlewareConfig) ProvideLogger() Middleware {
    return &LoggerMiddleware{}
}

// flora:order=2
func (c *MiddlewareConfig) ProvideAuth(repo *Repository) Middleware {
    return &AuthMiddleware{repo: repo}
}

// Flora automatically bundles Logger and Auth into a sorted slice!
func NewServer(middlewares []Middleware) *Server {
    return &Server{chain: middlewares}
}

---

Learn by Example

The best way to master Flora is by looking at the provided examples. Check out the /examples directory in this repository. It contains focused, runnable scenarios ranging from basic to advanced:

• 01_basic_component: The absolute basics. Struct embedding, interfaces, and auto-wiring.
• 02_configuration: How to use @Configuration to integrate external packages and manage graceful shutdowns (cleanup func()).
• 03_prototypes: How to generate and inject Factory closures (func() (*Struct, error)) instead of Singletons.
• 04_slices: How to utilize Multi-Binding to automatically collect and sort plugins/middlewares into a slice.
• 99_webapp: (Recommended) A simple REST API implementing routing, middlewares, and a mock database.

---

License & Acknowledgments

Flora is released under the Apache 2.0 License.

Flora builds its foundation upon Google Wire. While Flora provides the auto-discovery, AST parsing, and the highly automated developer experience, the actual generation of the static dependency graph is powered by Wire.

Documentation

Overview

Copyright © 2026 Soner Astan astansoner@gmail.com

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Index

• type Component
• type Configuration

Types

type Component

type Component struct{}

Component is a marker struct designed to be embedded into your own domain structs (e.g., Services, Repositories, Handlers). Embedding this tells Flora's AST scanner to automatically discover the struct, find its constructor, and wire its dependencies.

By default, Flora looks for an exported function named 'New<StructName>' (e.g., NewUserService), treats the component as a Singleton, and automatically binds it to any interfaces it implements.

You can customize this behavior using the `flora` struct tag:

type MyService struct {
	flora.Component `flora:"primary,scope=prototype,constructor=BuildService,order=1"`
}

Clean Architecture & Type Aliasing: To prevent framework pollution in your core domain, Flora fully supports Go Type Aliases. You can define a neutral alias (e.g., `type DIComponent = flora.Component`) in your domain and embed that alias instead. Flora's AST scanner will automatically resolve it.

Available Tag Options:

• constructor=<Name>: Overrides the default constructor lookup (e.g., constructor=BuildMyService).
• primary: Marks this component as the primary implementation of an interface to resolve collisions.
• scope=prototype: Changes the lifecycle from Singleton to a Factory (fresh instance per injection).
• order=<Number>: Defines the exact sorting position when injected as part of a Slice ([]Interface).

type Configuration

type Configuration struct{}

Configuration is a marker struct designed to be embedded into configuration provider structs. It is strictly meant for integrating third-party types (like *sql.DB), functional adapters (like HTTP middlewares), or any types you do not own and cannot embed flora.Component into.

Flora scans all exported methods of a Configuration struct and registers their return types as providers in the DI container.

Because Go does not allow struct tags on functions, you configure these provider methods using "Magic Comments" placed immediately above the method signature.

Example:

type DatabaseConfig struct { flora.Configuration }

// flora:primary,scope=prototype
func (c *DatabaseConfig) ProvideDatabase() *sql.DB { ... }

Clean Architecture & Type Aliasing: Just like flora.Component, you can use a Go Type Alias (e.g., `type DIConfig = flora.Configuration`) to keep your architecture strictly decoupled from the framework.

Available Magic Comments:

• // flora:primary : Marks the returned type as the primary implementation to resolve collisions.
• // flora:scope=prototype : Changes the lifecycle to a Factory (fresh instance per injection).
• // flora:order=<Number> : Defines the exact sorting position when injected via Slice ([]Interface).