Drupal 8

When developing plugins in Drupal a common task is to inject context so that certain tasks can be performed.

For example, we might have a block plugin that needs to know about the content entity of the page it is currently being rendered on. We could potentially inject the routing system into the plugin and use this to find the currently loaded entity, but there is a drawback to this. There is a fair amount of custom logic involved in finding the content entity from the route and we would need to use this same code every time we want to solve this problem.

This method also hard codes the route into the plugin and so makes it difficult to select any other sort of context. There is also a problem when it comes to caching as you also need to inform the plugin about the use of routing so that the caching layers know how to cache things.

Whilst working on a module I found that I needed to do something that was difficult to find information for. I think part of that is because the solution is simpler than I was thinking, but it did cause me to get lost in source code and internet issues for a while.

What I needed to do was to load in a list of configuration entities that matched certain parameters. The configuration entity I was dealing with was used to manipulate the output of a form, but only if certain conditions were met first. I thought that this information might be useful to others who are looking to load configuration entities.

I have been using the Drupal dependency injection system for a while now, even giving talks and writing articles on the subject. As the release of Drupal 10 is just around the corner I have been thinking more about how to override dependencies to plugin classes.

I wanted to share a trick to overriding dependency injection that will make your life easier. The Drupal codebase itself does not use this trick, but it seems that many contributed modules have started to use this trick to create plugin classes.

In this article I will go through how to add dependency injection to Drupal classes in two different patterns.

Drupal has a number of coding standards and best practices that govern the way code should be written. This has many benefits but can allow for a consistent and maintainable code to be created.

All Drupal modules and themes are written with coding standards in mind and that allows Drupal developers to look at any project and see a similar style of code. If you ever submit code to Drupal or a contributed project you will be required to adhere to these coding standards, so it makes sense to get used to knowing about them.

The main tool that is used to test coding standards in Drupal is PHP_CodeSniffer, which is a widely used static analysis tool for testing PHP coding standards. It comes with a set of coding standards built in, but it is possible to add the Drupal coding standards for the tool to use.

Client requirements can be complex and those complex requirements often require custom code to be written. This includes making sure that the editing process conforms to certain validations.

Drupal can easily handle simple validation like having a value in the field or making sure an email is valid, but with more complex validations usually require custom code.

Whilst it is possible to inject custom validators into form submissions, I find using validation constraint classes makes the whole process much more predicable. Also, validation constraints are applied at a lower level than form validations, which means we can validate the data is correct even if we are creating the entity from an API. 

Derivers in Drupal are one of the ways in which you can inform Drupal about the presence of plugin types. This allows you to generate multiple custom types of a plugin so that it can be represented as multiple different plugins within the system.

Perhaps the most useful deriver example I have seen is the menu deriver. This allows us to use the Drupal plugin architecture to generate custom menu links.

If you want to create a menu link for your module then you would normally add them one at a time to a *.links.menu.yml file. This is an example of using the menu links plugin system to inform the menu system about the links you want to add.

PHPStan is a great command line tool for looking at how your PHP code will run without actually running it. It's great for finding potential bugs that you wouldn't have otherwise discovered using other tools or through unit testing.

With regards to Drupal projects there is a little problem in that PHPStan doesn't know how to interpret Drupal plugins, entities, controllers or all the other Drupal architecture that goes into a Drupal module. For this reason, if you try to run PHPStan on your module code you'll find that it produces a lot of errors regarding missing objects or incorrect parameters.

Thankfully, it's possible to easily teach PHPStan about Drupal and make the tool more useful when writing Drupal code. First we need to install it.

Custom Drupal codebases (or any codebases really) can be difficult to maintain. New developers to the system need to familiarise themselves with how the code works and what the system is doing before they can make any contributions.

What makes things more difficult is when a site with lots of custom code has modifications that adapt the functionality to specific users.

I will occasionally come across sites that provide some sort of service, but have made modifications to their code that changes things for a particular user (or set of users). This is often to appease the largest user base on the system that wants things done in a certain way, but the site is unwilling to change things for all users.

Creating a Drupal site can be a complex process. Some people put together Drupal sites using a collection of different modules whilst others use Drupal as a framework and build the site using code.

No matter what sort of Drupal site you have, you'll need to have some testing in place to make sure that it works correctly. This is especially important when applying updates to your sites as the updated code can create unwanted side effects (or contain bugs) that might cause the site to malfunction. Generally, Drupal modules are very good with updates, but there are sometimes interactions between modules can cause problems that weren't taken into account.

When it comes to testing, there are a number of different options available to a Drupal developer. Each of which have their own uses and depend on the type of Drupal site you are trying to test.

In this article, I will go through a number of testing strategies that you can use to test a Drupal site. I won't delve too deep into each topic as this is more of an overview of the different technologies and strategies available.

I was recently working with a Drupal 9 site and found some strange behaviour when saving certain types of content. The page would appear to save, but much of the content appeared to be missing. It had even failed to generate the paths for the page based on the path auto rules.

Digging deeper I found the root cause of the problem was an improperly created redirect in an insert hook within custom code written on the site. This code looked for the creation of a particular content type and then forced the redirect to happen.