If you are a developer new to Magento 2, you are probably wondering how to create a Magento 2 Composer Module. Hopefully the below steps will be useful to you. This is how I managed to do it, eventually.

First of all, you should familiarise yourself with composer, and it’s basic usage.

This guide asumes you’ve already installed and configured a vanilla Magento 2 project. If you haven’t done that yet, I’d advise you to check this out and follow the official guide. Feel free to drop me a line if you have any issues.

I’ve found quite a few sites that show how to create a Magento 2 module “the old way”, by copying the module contents inside app/code folder (note that in Magento 1.x it used to be app/code/codePool, but that doesn’t exist anymore in Magento 2).

However, as I’ve recently been working on Symfony 2 projects, I’m quite used to composer, and it’s usage to easily integrate third party components/packages. So, once I saw the file “composer.json” on the root directory of Magento 2, I knew that it should be the way forward in order to develop Magento 2 extensions.

Let’s get started. I’m assuming you’ve developed already your Magento 2 extension, as the purpose of this guide is to show how to package the extension within a composer (sub) module, and the creation of an extension would go beyond the scope of this post. Check this guide to find out how to create a Magento 2 extension, or just clone it’s source code from github.

• To begin with, you should create a new (github/bitbucket…) repository, and place your source code inside.
• In the root folder, create a new file named composer.json. This fille will describe the details of your package. This is how mine looks like:

  {
      "name": "lumbrales-software/magento2-first-module",
      "description": "Hello world Magento 2 Composer Module!",
      "require": {
          "magento/project-community-edition": "*"
      },
      "type": "magento2-module",
      "version": "0.1.0",
      "extra": {
          "map": [
              [
                  "*",
                  "Yourcompany/YourModule/"
              ]
          ]
      },
      "authors": [
          {
              "name": "Javi Lumbrales",
              "homepage": "https://www.lumbrales-software.com/",
              "role": "Developer"
          }
      ]
  }

  The most important parts described below:

  • The name of the package: This will serve as identifier of your package, and will be used later on.
  • Requirements: We’ve added “magento/project-community-edition” as a requirement, as this module requires Magento 2 in order to work.
  • Type: We specify “magento2-module” so that it’s contents are copied to app/local once the package is installed (more about this later).
  • Version: Not important, as we’ll use git tagging to handle the composer module updates.
  • Extra: – Map: This tells composer to copy all (*) contents into app/code/LumbralesSoftware/HelloWorld, so the root of your extension should be structured already. This means that you don’t need to keep your files under app/code/YourCompany/YourModule in your repository. Instead, they should be in the root straightly. This is how it your repository should look like:

Repository Root:
Block/
Controller/
etc/
…

• Push all your code to the master branch (I’ll explain the tagging on a separated post later on)
• Go to the root folder of your Magento 2 installation, and type the following commands in your terminal:

composer require magento/magento-composer-installer

This is a submodule required to properly install third party Magento 2 extensions as composer submodules (Remember the type:magento2-module mentioned at the beginning).

• Then, as your module is still not in a packages repository such as packagist.org, or packages.magento.com, you need to specify your own VCS repository so that composer can find it. In the repositories section of the composer.json file of the Magento 2 project (if the repositories section doesn’t exist, create it, else, add your repository at the end) add the following:

 "repositories": [
    {
      "type": "vcs",
      "url": "https://github.com/youraccount/yourmodule-repository"
    }
  ],

• Since your package is in a development stage, you will need to add the minimum-stability as well to the composer.json file:

"minimum-stability": "dev",

Note that this could be removed later on, once we have properly tagged/released a stable version of our package/extension.

• After that, you should be able to install your module as follows (remember how you named it):

composer require your-package/name #In our example the name was lumbrales-software/magento2-first-module

The above command should download your module and copy it’s content to app/code/YourCompany/YourModule

• Last, but not least, you will need to enable your module and clear Magento cache. Add a new entry in app/etc/config.php, under the ‘modules’ section (Magento 2 project):

  'Yourcompany_YourModule' => 1,

Note that this name should match with the name that you’ve put on the composer.json, section extra -> map.

That’s it, after that your module should be ready to go.

You can download the source code of my Magento 2 Composer Module sample here.

I hope it helps, and let me know if you have any issues!

In my next post I’ll show a basic usage of git tagging and composer to be able to easily release your module updates.

Credits:
https://www.ashsmith.io/2014/12/simple-magento2-controller-module/
https://alankent.wordpress.com/2014/08/03/creating-a-magento-2-composer-module/