Form Alters as Services

Would you like to define well-known form alters as services? This project for you. From ID, base ID and prioritization supported.

General recommendations

• Install this module only via Composer since it has a third-party library in dependencies which will not be downloaded in any other way and you will get not working solution.
• Try to avoid usage of this utility in your contributed projects since it may discourage and/or break the behavior of Drupal. The most suitable area for usage - custom code.

Usage

How to deny particular service from being used?

Implement the hasMatch() method in your service and decide there whether service is applicable.

How to define validation/submission handlers?

This is achievable with annotations: @FormValidate and @FormSubmit. Using one of them you can declare a public method of your service to be a handler.

Please note, that every handler can be configured via annotation properties. If you want to add it to the beginning of the handlers list, set the strategy to prepend (append by default). Moreover, you can define a priority using self-titled property.

Isolated calculation of priorities

IMPORTANT: Remember that priority calculation of handlers occurs for every service separately. This means that you cannot put your handler before/after one from another service in case its priority is higher/lower.

Handlers invocation

IMPORTANT: Sometimes you might found out that validate/submit handlers are not executing. The reason of this is an architecture of Drupal. If a clicked button within the form contains its own #validate and/or #submit list of handlers it will mean that all global will be ignored. To deal with such cases you need to put your own handlers programmatically (in alterForm() method) for necessary buttons.

Programmatic definition of a service

my_module.services.yml

services:
  form_alter.node_form:
    class: Drupal\my_module\NodeFormAlter
    arguments:
      # Base form ID. An exact form ID could be used as well. To compute availability in runtime use "match" special keyword.
      - 'node_form'
    tags:
      - name: form_alter
        # Non-required property (0 by default).
        priority: 4

src/NodeFormAlter.php

namespace Drupal\my_module;

use Drupal\Core\Form\FormStateInterface;
use Drupal\form_alter_service\FormAlterBase;

class NodeFormAlter extends FormAlterBase {

  /**
   * {@inheritdoc}
   */
  public function alterForm(array &$form, FormStateInterface $form_state): void {
  }

  /**
   * @FormValidate(
   *   priority = -5,
   *   strategy = "append",
   * )
   */
  public function nameOfValidateHandler1(array &$form, FormStateInterface $form_state): void {
  }

  /**
   * @FormValidate(
   *   priority = 1,
   *   strategy = "append",
   * )
   */
  public function nameOfValidateHandler2(array &$form, FormStateInterface $form_state): void {
  }

  /**
   * @FormSubmit(
   *   strategy = "prepend",
   * )
   */
  public function nameOfSubmitHandler1(array &$form, FormStateInterface $form_state): void {
  }

  /**
   * @FormSubmit()
   */
  public function nameOfSubmitHandler2(array $form, FormStateInterface $form_state): void {
  }

}