Feature: #107759 - TranslateViewHelper supports Translation Domain syntax

Description

The Fluid <f:translate> ViewHelper now supports the new Translation Domain syntax, providing a more concise and readable way to reference translation labels.

A new domain attribute has been added that accepts both traditional extension names and the new translation domain names.

The ViewHelper now supports multiple ways to specify translations:

New domain attribute - Recommended for new code:

<f:translate key="form.legend" domain="my_extension" />
<f:translate key="form.legend" domain="my_extension.messages" />

Inline domain syntax in key - Shortest form:

<f:translate key="my_extension.messages:form.legend" />
<f:translate key="LLL:my_extension.messages:form.legend" />

Traditional extensionName attribute - Still supported:

<f:translate key="form.legend" extensionName="MyExtension" />
<f:translate key="form.legend" extensionName="my_extension" />

Full LLL reference - Classic syntax, still supported:

<f:translate key="LLL:EXT:my_extension/Resources/Private/Language/locallang.xlf:form.legend" />

Domain Attribute Priority

When both domain and extensionName are provided, the domain attribute takes precedence:

<!-- Uses "other_extension.messages" domain, not "MyExtension" -->
<f:translate key="label" domain="other_extension.messages" extensionName="MyExtension" />

Automatic Domain Detection

If neither domain nor extensionName are specified, the ViewHelper attempts to automatically detect the translation domain from the context:

Extbase context: Uses the controller extension name
Key with domain prefix: Extracts domain from key="domain:id" syntax
LLL reference: Parses the extension key from the file path

Examples

Using domain attribute with full domain name

You can specify the exact translation domain including resource names:

<f:translate key="menu.item" domain="backend.toolbar" />
<!-- Resolves to: EXT:backend/Resources/Private/Language/locallang_toolbar.xlf -->

Inline domain syntax in key

The shortest form combines domain and key directly:

<f:translate key="core.form.tabs:general" />
<!-- Resolves to: EXT:core/Resources/Private/Language/Form/locallang_tabs.xlf -->

With arguments and default values

All existing ViewHelper features work with the new syntax:

<f:translate
    key="users"
    domain="backend.messages"
    arguments="{0: count}"
    default="No users found"
/>

Using variables for domain

Dynamic domain selection is supported:

<f:translate key="label.title" domain="{myDomain}" />

Migration from extensionName

Existing code using extensionName continues to work without changes. However, new code should prefer the domain attribute combined with translation domain syntax for better readability:

Before:

<f:translate key="LLL:EXT:my_extension/Resources/Private/Language/locallang_form.xlf:legend" />
<f:translate key="legend" extensionName="MyExtension" />

After:

<f:translate key="my_extension.form:legend" />
<f:translate key="legend" domain="my_extension.form" />

Impact

The <f:translate> ViewHelper now provides a more convenient and readable way to reference translations using the new translation domain syntax. This reduces verbosity in Fluid templates and aligns with modern translation system conventions used in Symfony and other frameworks.

All existing syntax forms remain fully supported, ensuring backward compatibility. The new syntax can be adopted incrementally within a project, and both old and new forms can coexist in the same template.