Deconfig

Drupal 8's configuration management is great for controlling site configuration, but sometimes a developer wants to loosen the shackles on certain configuration items and let the site administrator change the setting without it being overwritten by the configuration management system on the next configuration sync.

As a safety measure, it requires the hidden configuration not to be present in the config sync storage so it's obvious for developers that the given configuration is not enforced. It will throw an error if it encounters a hidden config item in config sync, which will cause drush cim/drush cex to error out.

Deconfig'ing configuration

In order to deconfig, simply add a _deconfig entry to the file in the config sync storage file specifying what to deconfig, and remove the configuration. The _deconfig item duplicates the hierarchy of the configuration, allowing for deconfig'ing the entire file or individual items.

The values of _deconfig are strings that ideally should describe why the item was hidden.

Examples

To deconfig whole file:

_deconfig: 'Hide this configuration'

To deconfig site mail and front page in system.site.yml:

_deconfig:
  mail: 'Let editor configure site email'
  page:
    front: 'Let editor configure frontpage'
name: 'Le site'
slogan: 'One site to rule them all'
page:
  403: ''
  404: ''
admin_compact_mode: false
weight_select_max: 100
langcode: en
default_langcode: en

Soft deconfig

In some instances a configuration cannot be completely removed from configuration, either because something requires the item to be present (site.name, for instance, is required to be present in the exported configuration in order to install a site from configuration), or because it needs a default value to work.

In these cases deconfig support a "soft" deconfig mode which allows the setting to be present, but only used when there's no value in the active configuration. The default values wont get overwritten when exporting the configuration.

Simply add a @ to the key of the item (remember to quote the name.):

_deconfig:
  '@name': 'Let administrator configure site name'
name: 'Default site name'
...

Drush commands

drush deconfig-remove-hidden: Clean up command that'll remove any deconfig'ed configuration from config sync. This is the easy way out of cim/cex throwing errors.

Implementation details

Deconfig does its magic by implementing a config.storage.sync storage that reads deconfig'ed configuration from the active storage rather than the sync storage, so they will always appear to be up to date.