Empty Category Messages: Technical Details

Flow, plugin structure, custom fields, security and scope of the plugin: subscriber, service, Twig extension, template and lifecycle.

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Technical Details

Package and plugin class

Property	Value
Composer package	`mmd/sw67-empty-category`
Plugin class	`Mmd\EmptyCategory\MmdEmptyCategory`
Technical plugin name	`MmdEmptyCategory`
Namespace	`Mmd\EmptyCategory`

Flow

graph TD
    A["Category page requested"] --> B["NavigationPageLoadedEvent"]
    B --> C["CategoryPageSubscriber loads parent chain and media"]
    C --> D["Listing template: block element_product_listing_col_empty"]
    D --> E["Twig function mmd_empty_category_message"]
    E --> F["EmptyCategoryMessageService resolves the message"]
    F --> G{"Message found?"}
    G -->|"Yes"| H["Render custom message"]
    G -->|"No"| I["Shopware default message"]

Building blocks

Class / file	Purpose
`Subscriber\CategoryPageSubscriber`	Listens to `NavigationPageLoadedEvent`. Loads the parent categories (up to 10) only when inheritance is enabled on the category. Loads the media of the images as soon as a message, image or inheritance is set
`Service\EmptyCategoryMessageService`	Resolves the message: own message, otherwise inheritance upwards, otherwise empty. The search covers at most 10 levels including the category itself, so at most 9 parent categories are reached. Sanitizes CSS classes and select values
`Service\EmptyCategoryMessage`	Immutable value object with message, image URL, CSS classes, size and alignments
`Twig\EmptyCategoryExtension`	Registers the Twig function `mmd_empty_category_message`
`views/storefront/component/product/listing.html.twig`	Overrides the block `element_product_listing_col_empty`
`app/storefront/src/scss/base.scss`	Styles for the plugin classes
`MmdEmptyCategory`	Creates the custom field set, completes it on update and removes it on uninstall

Custom fields

The set mmd_empty_category is assigned to the category entity and contains the fields listed under Configuration. The values are stored in the customFields field of the category.

Scope of the plugin

Area	Status
Plugin settings (config.xml)	none
Own routes and API endpoints	none
Own database tables and migrations	none
Admin modules and permissions (ACL)	none, the fields appear in the existing category editor
Scheduled tasks and commands	none
External requests	none
Snippets	`mmd.emptyCategory.imageAlt` (de-DE, en-GB)

Security

The message is output through the sw_sanitize filter.
CSS classes are reduced to letters, digits, hyphens, underscores and spaces.
Select field values are checked against the allowed values, otherwise the default applies.
The image is resolved via the media manager and its URL is escaped as an HTML attribute.
There are no inline styles, so the plugin is compatible with a strict Content Security Policy.
The plugin does not process personal data.