hook_node_view_alter not working

Question

I'm hoping to finally find some solutions here. I'm new to custom module development in Drupal and I'm trying to learn the basics. What I'm trying to do is use hook_node_view_alter, however even at the simplest step (showing a status message) it does not work.

My module (test_module) is installed and enabled on the site. Currently the custom module has only two files: test_module.info.yml and test_module.module

Code from test_module.info.yml file

name: test_module
type: module
description: Test module
core: '8.x'

Code from test_module.module file

<?php
/*
* Implementation of hook_node_view_alter
*/

use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\NodeInterface;


function test_content_node_view_alter(array &$build, NodeInterface $node, EntityViewDisplayInterface $display, $view_mode) {
    drupal_set_message(t('Hello!'));
}

?>

It doesn't show the message when I'm opening a node (/node/1) at my Drupal site. As I understand it, it should show the message for any existing node when it is viewed. I've cleared the cache, nothing's changed.

---

Update

• changed test_content_node_view_alter() to test_module_node_view_alter()
• adjusted the code to coding standards
• removed the php closing tag

My code in test_module.module looks like this right now:

<?php

/**
 * @file
 * Implementation of hook_node_view_alter();
 */

use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\NodeInterface;

function test_module_node_view_alter(array &$build, NodeInterface $node, EntityViewDisplayInterface $display, $view_mode) {
  drupal_set_message(t('Hello!'));
}

I've cleared all cache and now the website gets this error:

The website encountered an unexpected error. Please try again later.

Answer 1

After researching more examples out there in the Web, I've finally managed to make this work, however I'm still not sure why it was not working before...

Working code:

<?php

/**
 * @file
 * Implementation of hook_entity_view_alter();
 */

function test_module_entity_view_alter($entity, $type, $view_mode) {
    drupal_set_message(t('Hello world!'));
}

Moving on to further modifications. Thanks everyone!

Answer 2

You need replace

function test_content_node_view_alter(array &$build, NodeInterface $node, EntityViewDisplayInterface $display, $view_mode) {
    drupal_set_message(t('Hello!'));
}

to

 /**
 * Implements hook_entity_view().
 */
  function test_module_entity_view(array &$build, NodeInterface $node, EntityViewDisplayInterface $display, $view_mode) {
        drupal_set_message(t('Hello!'));
  }

hook_node_view() it's invoked has just changed. As you mentioned, it's now handled by hook_ENTITY_TYPE_view(). or hook_entity_view()

Answer 3

This DOES still work in D8 and D9 :)

function MYMODULE_node_view_alter(array &$build, Drupal\Core\Entity\EntityInterface $entity, \Drupal\Core\Entity\Display\EntityViewDisplayInterface $display) {
  if ($entity->bundle() == 'company') {
    \Drupal::messenger()->addMessage(t('Hello!!!'));
  }
}