How to patch a core controller, model, block or helper in Magento 2

Question

How to create a custom patch file for Magento 2?

Answer 1

Patching core Magento 2 files

Composer includes repositories in order of preference, meaning you can add a repository to pull from ahead of Magento’s – for specific modules.

This means that you could copy the module into your own git repository, include it ahead of the Magento version of the module and apply your patches into it.

You need to:

• Remove the package from your vendor/magento folder if you’ve already installed it.
• Add the url of your Git repository in the repositories list in composer.json (before repo.magento.com).
• Add a require reference for the modules you’ve patched, i.e. magento/module-catalog, or magento/module-cms with the version number required.

This situation isn’t ideal. If you want to upgrade Magento at some point, there is a likelihood that Magento will update the core module that you’ve patched. This means that you would need to download a new version of an entire module, inspect it, patch it, and update your repository. You’d then need to match verison numbers in your composer.json file and ensure that there were no conflicts.

You could simply ignore composer entirely, and include everything within source control. This would allow you to patch any required files, and simply roll them out across enviornments. This becomes a problem moving forward however when you upgrade your store, or you try to bolt something on, and something within core doesn’t play along quite as expected. It does mean however, with good branching, documentation and commit messages, you could keep track of what you’d patched and repatch if/when required.

Apply Patch files

As Composer is being used within the solution, it would be great if we could run a patch file every time that Composer install or Composer update is run. This would mean that we wouldn’t have to setup a new repository for a module, (potentially per a project) – we could include the patch within the source control for the site.

If we upgrade Magento, then we don’t have a whole module to go through and check, we just have the small (compared to the whole module) amount of code to review. We can see at this point whether the patch is still required – rewriting it if neccessary.

So, how can we do this?

Luckily, there’s already a Composer plugin that can do it for us.

  https://github.com/cweagans/composer-patches

This plugin allows us to apply patches both from local and external sources when a composer install or composer update is made.

Firstly, tell composer to include the compose-patches module:

composer require cweagans/composer-patches

You should see this as a new entry in your composer.json file now.

Next, you need to get a patch file for what you’re wanting to patch. In this example, I’ll reference https://raw.githubusercontent.com/allanpaiste/magento2-patches/master/Patch-Magento_Catalog-M2.1.0-image-attribute-backend-model-hardcoded-attribute-code-removal.patch

Fun fact – if you find any PR on Github, simply add “.patch” onto the URL for a full diff patch file.

Add your patch into a “patches” folder in your Magento document root. You could sub folder this depending on how many patches you have so that things are organised, but a naming convention on your patch files should be enough.

Once this is done, you need to tell composer.json about the patch that it needs to include

"require": {
   ....
}
"extra": {
     "magento-force": "override",
     "patches": {
         "magento/module-catalog": {
             "Fix: https://github.com/magento/magento2/issues/5438":
             "patches/Patch-Magento_Catalog-M2.1.0-image-attribute.patch"
         }
     }
 }

Here, we’re telling the patch system to patch "magento/module-catalog" with the patch file found in "patches/Patch-Magento_Catalog-M2.1.0-image-attribute-backend-model-hardcoded-attribute-code-removal.patch"

• Next, just run a composer update.

References:

https://www.pinpointdesigns.co.uk/patching-core-magento-2-files/

https://devdocs.magento.com/guides/v2.3/cloud/project/project-patch.html

https://support.magento.com/hc/en-us/articles/360005484154-Create-a-patch-for-a-Magento-2-Composer-installation-from-a-GitHub-commit

I try to cover all concepts and I hope this will help