Feature: #96812 - Override backend templates with TsConfig

See forge#96812

Description

Introduction

All Fluid templates rendered by backend controllers can be overridden with own templates on a per-file basis.

This can be configured using TsConfig: Both PageTsConfig and UserTsConfig are observed. The feature is available for basically all core backend modules, as well as the backend main frame templates. Exceptions are email templates and templates of the install tool.

This feature was previously available in a similar way for some specifically crafted backend controllers, namely the dashboard extension and the page module. It was based on frontend TypoScript in combination with Extbase magic. This has been superseded by the new TsConfig based approach. Instances using the old solution need an adaption. Please find details in the changelog entry.

Note

While this feature is powerful and allows overriding nearly any backend template, it should be used with care: Fluid templates of the core extensions are not considered API. The core development needs the freedom to add, change and delete Fluid templates any time, even for bugfix releases. Template overrides are similar to an XCLASS in PHP - the core can not guarantee integrity on this level across versions.

Basic syntax

The various combinations are best explained by example: The linkvalidator extension (its composer name is "typo3/cms-linkvalidator") comes with a backend module in the "Web" main section. The page tree is displayed for this module and linkvalidator has two main views and templates: Resources/Private/Templates/Backend/Report.html for the "Report" view and another one for the "Check link" view. To override the Backend/Report.html with an own template, this definition can be added to an extensions Configuration/page.tsconfig file (see changelog):

# Pattern: templates."composer-name"."something-unique" = "overriding-extension-composer-name":"entry-path"
templates.typo3/cms-linkvalidator.1643293191 = my-vendor/my-extension:Resources/Private/TemplateOverrides

When the target extension identified by its composer name "my-vendor/my-extension" provides the file Resources/Private/TemplateOverrides/Templates/Backend/Report.html, this file will be used instead of the default template file from the linkvalidator extension.

All core extensions stick to the general templates, layouts and partial file and directory position structure. When an extension needs to override a partial that is located in Resources/Private/Partials/SomeName/SomePartial.html, and an override has been specified like above to my-vendor/my-extension:Resources/Private/TemplateOverrides, the system will look for file Resources/Private/TemplateOverrides/Partials/SomeName/SomePartial.html. Similar for layouts.

The path part of the override definition can be set to whatever an integrator prefers, Resources/Private/TemplateOverrides is just an idea here and hopefully not a bad one, further details rely on additional needs. For instance, it is probably a good idea to include the composer or extension name of the source extension in the path (linkvalidator in our example), or when using overrides based on page ids or group ids, to include those in the path. The source extension sup-path is automatically added by the system when looking for override files, when a layout file is located at Resources/Private/Layouts/ExtraLarge/Main.html, and an override definition uses path Resources/Private/TemplateOverrides, the system will look up Resources/Private/TemplateOverrides/Layouts/ExtraLarge/Main.html.

Templates overrides are based on file-existence: Two files are never merged. An override definition either kicks in because it actually supplies a file at the correct position with the correct file name, or it doesn't and the default is used. This can become unhandy for big template files. In such cases it might be an option to request a split of a big template file into smaller partial files, so an extension can override a dedicated partial only.

When multiple override paths are defined and more than one of them have overrides for a specific template, the override definition with the highest numerical value wins:

templates.typo3/cms-linkvalidator.23 = other-vendor/other-extension:Resources/Private/TemplateOverrides/Linkvalidator
templates.typo3/cms-linkvalidator.2300 = my-vendor/my-extension:Resources/Private/MyOverrideIsBigger

Due to the nature of TsConfig, and its two shapes PageTsConfig and UserTsConfig, various combinations are possible:

  • Define "global" overrides with PageTsConfig in page.tsconfig of an extension. This works for all modules, no matter if the module renders a page tree or not.

  • Define overrides on page level using the TSconfig field of page records. As always with PageTsConfig, sub pages and sub trees inherit these settings from parent pages.

  • Define overrides on user or (better) group level. As always, UserTsConfig can override PageTsConfig by prefixing any setting available as PageTsConfig with page. in UserTsConfig. A UserTsConfig template override thus starts with page.templates. instead of templates..

Usage in own modules

Extensions with backend modules that use the Simplified backend module template API automatically enable the general backend template override feature. Extension authors do not need to further prepare their extensions to allow template overrides by other extensions.

Impact

Third party or custom extensions like a site extension can now change backend templates if needed. This can be handy to for instance give editors custom hints in certain areas without custom PHP code, or to do some other quick solutions.

Some core extensions like the dashboard also use this feature when third party extensions supply additional widgets with templates to register those templates into the dashboard namespace. See the dashboard extension documentation and this changelog for more details.

This feature needs to be used with care since the core does not consider templates as API and a template override may thus break anytime.