[BUG] AppHook'ed Views can't use placeholders in their templates

[jrief]

Description

An AppHook'ed View can't use any CMS placeholders in their templates anymore.

This used to work in CMS version 3.

Steps to reproduce

• Create an AppHook class and register it
• Method get_urls of that class returns a list of urlpatterns.
• The URL attached to the CMS page typically looks like

@apphook_pool.register
class MyApp(CMSApp):
    def get_urls(self, page=None, language=None, **kwargs):
        return [
            ...,
            path('', MyView.as_view()),
            ...,
        ]

Now if the MyView class defines a template and that template contains a CMS {% placeholder … %}-templatetag, then function get_declared_placeholders_for_obj raises an exception.

There is a workaround by populating the toolbar with the current PageContent object, but in my opinion this should be part of the CMS logic and must not be done by the application.

Expected behaviour

No exception and the name placeholder should be editable.

Do you want to help fix this issue?

• Yes, I want to help fix this issue and I will join #workgroup-pr-review on Slack to confirm with the community that a PR is welcome.
• No, I only want to report the issue.

[fsbraun]

Apphooks should use the render_placeholder template tag. The reason is that the placeholders must be attached to the right model - and for your apphook it should be its model (not the PageContent). In django CMS 4 also models that are not rendered in views can be frontend editable (such as alias).

To resolve this, you will need to add a get_template() method to the model of your apphook, like, e.g.,

def get_template(self):
    return "my_app/model_content.html"

and in my_app/model_content.html you'll just place the placeholder (nothing else), e.g. (taken from djangocms-alias),

{% load cms_tags %}{% placeholder "content" %}

Your apphook will have to have a model that has a PlaceholderRelationField as described in the docs here.

The get_template part is something that still needs to go into the docs...

[jrief]

Apphooks should use the render_placeholder template tag.

But how does one then edit the content of this placeholder? In CMS3 this content then was stored together with the page (aka. PageTitle).

I know that it also is possible to create placeholders outside the PageContent model, but that means adding another field, etc.

Anyway, I found a not very elegant solution. I created a mixin class to be added to the MyView class as specified above. This mixin class looks like:

class PageContentMixin:
    def render_to_response(self, context, **response_kwargs):
        if hasattr(self.request, 'toolbar'):
            match = resolve(self.request.path)
            if match.url_name == 'cms_placeholder_render_object_edit':
                page_content = PageContent.admin_manager.get(id=match.args[1])
            else:
                language = get_language_from_request(self.request, check_path=True)
                if hasattr(self, 'page'):
                    page_content = self.page.pagecontent_set.get(language=language)
                else:
                    page_content = self.request.current_page.pagecontent_set.get(language=language)
            self.request.toolbar.set_object(page_content)
        return super().render_to_response(context, **response_kwargs)

do you see any problems using this solution?

[fsbraun]

The toolbar is not necessarily available (or rather be an EmptyToolbar), I fear. Will that work with published pages and no user logged in? Also, it means that you cannot frontend edit your app's model since you replace the toolbar object.

While storing the placeholder in the page content apparently was possible, I am not sure if it ever was a documented feature. Additionally, there is only one page content object for the whole of the app which might provide many more URLs. The "right" way for me is to add the field to the model and have that migration. If you've got prepopulated fields, the migration might need some additional code to move the placeholders to the new model.

[jrief]

The "right" way for me is to add the field to the model and have that migration.

For a possible "Detail" view, adding a PlaceholderField to a model might be a viable solution. But how would you proceed if the Apphook's "root"-URL points onto a list view? This btw. is a typical use-case for Apphooks.

[marksweb]

As far as I was aware, placeholders couldn't/shouldn't have been used in CMS apps in version 3.

See the docs for "placeholders outside the cms" - https://docs.django-cms.org/en/latest/how_to/placeholders.html?highlight=placeholders%20outside%20cms

Placeholders can be viewed as containers for CMSPlugin instances, and can be used outside the CMS in custom applications using the PlaceholderField.

[jrief]

@marksweb The documentation you're referring to is for CMS3 and there I have no problems. I'm using CMS4 with versioning and there the trouble starts.

[makjaveli]

Your apphook will have to have a model that has a PlaceholderRelationField as described in the docs here.

The get_template part is something that still needs to go into the docs...

Ok, is there a working example of PlaceholderRelationField?

I unfortunately could not create one following the referred docs using django-cms 4.1.0 with a clean project and a simple apphook.

The main problem is that the resulting page is not 'editable' in the toolbar. I can provide my current non working example if useful.

[fsbraun]

@makjaveli I agree, a working example in the docs would make things a lot easier. It would be a great addition for the how-to section! For now, I am happy to try and help you out with your example.

[makjaveli]

@makjaveli I agree, a working example in the docs would make things a lot easier. It would be a great addition for the how-to section! For now, I am happy to try and help you out with your example.

That would be great. Here is the url to a minimal django-cms4 app_hook and render_placeholder example:

https://github.com/makjaveli/djangocms_apphook_renderplaceholder

It should be runable out of the box. All steps of the current documentation were applied but currently it is not working. The visible reason is that the page is not editable in the cms toolbar so no content can be added to the placeholder.

Any hints what is missing would be appreciated. I would also file a new issue if this is not directly related to this issue.

[fsbraun]

I've added this short issue here: #7736 Please feel free to comment.

To get you going quickly, I've created a PR for your example repo that does the trick. A few steps were necessary:

• Declaration of the Product model as frontend-editable in cms_config.py
• Adding a get_template() method to the model
• Adding a structure mode template for identifying the placeholders (shop_app/product.html)
• Adding a rendering method for the preview and edit endpoints
• Finally, to make the Preview and Edit buttons appear on the published URL: Add the product instance to the toolbar