Image properties are managed by themes

[ericmorand]

Violation

Magento 2 famework forces image properties to be managed by themes.

Why it is a violation of the Separation of Concerns principles

Image properties are declared in etc/view.xml, a file that is expected by Magento 2 framework to be provided by themes. This is documented in Configure theme properties.

This is a violation because image properties depend on image types, and image types are product attributes created either by modules or from the back-office. It makes the themes dependent on data that they are not managing themselves and can't be declared as dependencies.

Illustration of the violation

Consider the following etc/view.xml file, taken from the above documentation:

<images module="Magento_Catalog">
    <image id="unique_image_id" type="image">
        <width>100</width> <!-- Image width in px -->
        <height>100</height> <!-- Image height in px -->
    </image>
</images>

Here, a theme declares an image identifier named unique_image_id as a resized variant of the image image type. This image image type may or may not exist: if one of the installed module did create that image product attribute, or if that product attribute was created in the back-office, then unique_image_id is a perfectly valid image identifier; if no module did create the image product attribute and it was not created either from the back-office, then unique_image_id is not valid and trying to use it to create an image variant would lead to a crash.

It is impossible when writing a theme to know if a product attribute exists - and thus it is impossible to know if an image identifier declared in a theme will function or not.

In other words, having image identifiers managed by themes makes the behavior of the final product unpredictable.

Workarounds

It may be possible to declare image properties programmatically at modules level. This needs to be checked. If not, there is no workaround for this issue.

Proposed solution

• Override Magento 2 configuration resolvers to have image properties declared by modules instead of themes.
• Remove support for etc/view.xml by themes configuration resolvers.