How does the new config_exclude_modules setting work exactly?

Question

Drupal 8.8 introduced a new setting: https://www.drupal.org/node/3079028

By adding these lines to your settings.local.php I expected the modules and their configuration to be excluded from config export.

$settings['config_exclude_modules'] = ['kint', 'devel'];

However:

• kint and devel still appear in my core.extensions.yml
• Yaml files related to devel still get generated.
• Modules are still removed and installed based on the core.extensions.yml

How does this feature work?

Edit: I upgraded from Drupal 8.7, that seems to keep this function to work properly.

Answer 1

Enable the module and activate the filter by declaring $settings['config_exclude_modules'] in your settings.php file, eg:

$settings['config_exclude_modules'] = ['devel', 'stage_file_proxy'];

Now, when you export configuration (drush config-export), the selected modules should no longer show up in core.extension.yml and their configuration should not be exported.

Make sure first before doing that to remove these module from core.extensions.yml manually for the first time.

Update: It seems to be related to a drush issues: drush config:status does not respect excluded modules #4194

Answer 2

Addendum really, as I was looking at the logic in ExcludedModulesEventSubscriber that does most of the work for config_exclude_modules.

Say module foo has some config in config/install, and you exclude module foo and then install the module. The config that is installed from config/install will not necessarily be excluded by config_exclude_modules in the future.

For config to be excluded needs to belong to the module by name (foo.*) or there should be a dependency on the module in the config.

For example, say if your module foo installs a view that you would like to also be excluded config, then it will be excluded based on the dependencies of that view.

dependencies:
  module:
    - node
    - etc

However you can add an enforced dependency to prevent this.

dependencies:
  module:
    - node
    - etc
  enforced:
    module:
      - foo