fix: CarouselSlidePlugin and TabItemPlugin template retrieval to respect parent template setting

[Copilot]

Fix CarouselSlidePlugin and TabItemPlugin template retrieval issue

Problem

In version 2.0.0, CarouselSlidePlugin and TabItemPlugin stopped respecting their parent plugin's template setting when multiple templates are configured. This caused child plugins to always render using the first (default) template, regardless of which template was selected on the parent carousel or tab container.

For example, with the following configuration:

DJANGOCMS_FRONTEND_CAROUSEL_TEMPLATES = (
    ("default", "Default"),
    ("fancy", "Fancy"),
    ("minimal", "Minimal"),
)

Even when a Carousel is explicitly set to use the "fancy" template, all its slides would incorrectly render using the "default" template.

Root Cause

The issue was in the get_render_template() methods of both plugins. They were using:

instance.parent or instance

This returns instance.parent which is a CMSPlugin instance (the base model). The CMSPlugin model doesn't have a template field - only the actual plugin models (like Carousel or Tab) have this field in their configuration. Without access to the template field, get_plugin_template() falls back to first_choice(templates), always returning the first available template.

Solution

Changed the code to properly retrieve the actual plugin instance:

instance.parent.get_plugin_instance()[0] if instance.parent else instance

The get_plugin_instance() method returns a tuple of (plugin_instance, plugin_class). Using [0] extracts the actual typed plugin instance (e.g., Carousel) which has the template field, allowing the correct template to be used.

Changes

• Fixed CarouselSlidePlugin.get_render_template() in djangocms_frontend/contrib/carousel/cms_plugins.py
• Fixed TabItemPlugin.get_render_template() in djangocms_frontend/contrib/tabs/cms_plugins.py
• Added test test_carousel_slide_inherits_parent_template() to verify carousel template inheritance
• Added test test_tab_item_inherits_parent_template() to verify tab template inheritance
• Fixed flake8 compliance issues (removed unused import, fixed whitespace)

Notes

This fix aligns with the pattern already used in the framework render mixins (carousel/frameworks/bootstrap5.py and tabs/frameworks/bootstrap5.py) which correctly use instance.parent.get_plugin_instance()[0] to access the parent plugin.

The change is backward compatible - if no parent exists, it falls back to using the instance itself.

Fixes #313

Original prompt

---

This section details on the original issue you should resolve

<issue_title>CarouselSlidePlugin refers to wrong "slide.html" Template</issue_title>
<issue_description>With 2.0.0 and and changes in regards to #220, the following line breaks the retrieval of the correct slide.html Template for the CarouselSlidePlugin:

https://github.com/django-cms/djangocms-frontend/blame/2.0.0/djangocms_frontend/contrib/carousel/cms_plugins.py#L89

instance.parent seems to refer to the CMSPlugin model which does not have a "template" field (should refer to CarouselPlugin).

Therefore get_plugin_template() falls back to first_choice() and retrieves the wrong (first) slide.html, if you have multiple Carousel Templates defined in DJANGOCMS_FRONTEND_CAROUSEL_TEMPLATES.

Downgrading to 1.3.5 fixes the behaviour.

(django-cms==4.1.9)</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #313

---

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[fsbraun]

@copilot MAke changes flake8 compliant

[Copilot]

@copilot MAke changes flake8 compliant

Fixed flake8 compliance issues:

• Removed unused import of CAROUSEL_TEMPLATE_CHOICES
• Removed trailing whitespace from blank lines in test files

All modified files now pass flake8 validation with the project's configuration (max-line-length=120). Commit: (hash will be in next push)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.13%. Comparing base (9844b4c) to head (d97e331).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #314   +/-   ##
=======================================
  Coverage   89.13%   89.13%           
=======================================
  Files         124      124           
  Lines        3387     3387           
  Branches      288      288           
=======================================
  Hits         3019     3019           
  Misses        252      252           
  Partials      116      116           

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