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 DrupalCoreEntityDisplayEntityViewDisplayInterface; use DrupalCoreEntityEntityInterface; use DrupalCoreEntityNodeInterface;   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 DrupalCoreEntityDisplayEntityViewDisplayInterface; use DrupalCoreEntityEntityInterface; use DrupalCoreEntityNodeInterface;  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.