Allow customising the base URL and URL namespace for snippet views through SnippetViewSet

[laymonage]

As part of #10206. Incorporates #10178.

Similar to ModelAdmin.base_url_path, you can customise the base URL path for the snippets views by setting SnippetViewSet.base_url_path. You can also customise the URL namespace, something that couldn't be done in ModelAdmin without a custom URL helper class, by setting SnippetViewSet.admin_url_namespace. If left unset, they default to snippets/{app_label}/{model_name} and wagtailsnippets_{app_label}_{model_name}, respectively. If further customisation is needed (e.g. you need to compute the string based on the model), the SnippetViewSet.get_admin_base_path() and SnippetViewSet.get_admin_url_namespace() methods can be overridden.

In addition, you can also do the same with the chooser views through chooser_base_url_path, chooser_admin_url_namespace, SnippetViewSet.get_chooser_admin_base_path() and SnippetViewSet.get_chooser_admin_url_namespace().

Note:
I'm not sure whether we should support the customisations for the chooser through SnippetViewSet or shall we just tell developers to override the SnippetViewSet.chooser_viewset property.

---

I also found a bug where the permissions for snippets registered through wagtail_hooks.py might not be initialised properly if Wagtail has not scanned for hooks.

Please check the following:

• Do the tests still pass?¹
• Does the code comply with the style guide?
  • Run make lint from the Wagtail root.
• For Python changes: Have you added tests to cover the new/fixed behaviour?
• For front-end changes: Did you test on all of Wagtail’s supported environments?²
  • Please list the exact browser and operating system versions you tested:
  • Please list which assistive technologies ³ you tested:
• For new features: Has the documentation been updated accordingly?

Please describe additional details for testing this change.

Continuing from the test example in #10178.

from wagtail.snippets.models import register_snippet
from wagtail.snippets.views.snippets import SnippetViewSet


class PersonViewSet(SnippetViewSet):
    icon = "user"
    admin_url_namespace = "some_namespace"
    base_url_path = "deep/within/the/admin"
    chooser_admin_url_namespace = "my_chooser_namespace"
    chooser_base_url_path = "choose/wisely"


register_snippet(Person, viewset=PersonViewSet)

You should be able to:

from django.urls import reverse

assert reverse("some_namespace:add") == "/admin/deep/within/the/admin/add/"
assert reverse("my_chooser_namespace:create") == "/admin/choose/wisely/create/"

Footnotes

1. Development Testing ↩

2. Browser and device support ↩

3. Accessibility Target ↩

[laymonage]

Do we want to keep doing this? Or should we advocate for model.snippet_viewset.get_admin_url_namespace() etc.?

It is quite handy, but I'm not really a fan of doing too much patching on the model. Even more so now that we have a reference to the viewset through model.snippet_viewset, we can access all the configuration from there. (Speaking of which, I'm thinking whether it would be better to do the model.snippet_viewset patching from here instead.)

We don't have to remove this outright (in case people depend on it, even though these aren't documented), but I'd like us to have a preferred way to get these values.

The same goes to these as well:

wagtail/wagtail/snippets/models.py

Lines 90 to 93 in fdc36a6

	model.get_usage = lambda obj: ReferenceIndex.get_references_to(
	obj
	).group_by_source_object()
	model.usage_url = get_snippet_usage_url

If we remove (or at least move) those, then what register_snippet does is pretty much just registering a snippet model with a viewset, putting the model into a global list, and that's it, which sounds very nice.

[gasman]

I'm very much in favour of keeping as much of this as possible contained within the viewset class - patching the model with these methods seems like it was a necessary evil before we had an obvious place other than the model to hang this common functionality onto, but the viewset is the natural place for it now. I think it's reasonable to remove it outright - I can't imagine there being any expectation for these to be anything more than Wagtail-internal glue.

In an ideal world I'd like to see the snippet_viewset attribute dropped too, so that the view-level and model-level considerations are fully separate - but it sounds like it'd need some heavy refactoring of the bulk action views to make that happen, and patching a single snippet_viewset attribute is definitely a lot cleaner than patching multiple methods into the model.

[laymonage]

I think I'll do this in a separate PR, as the get_admin_url_namespace is still used in a few places in Wagtail.

In an ideal world I'd like to see the snippet_viewset attribute dropped too, so that the view-level and model-level considerations are fully separate - but it sounds like it'd need some heavy refactoring of the bulk action views to make that happen, and patching a single snippet_viewset attribute is definitely a lot cleaner than patching multiple methods into the model.

We might be able to get away with something simpler to achieve this, e.g. the idea in #10178 (comment):

Or something simpler, we could change the SNIPPET_MODELS global list into a dictionary that maps each model to the viewset instance? People who rely on get_snippet_models() will still be able to iterate through it like a list of models, but we will be able to do something like get_snippet_models()[MyModel] and get the viewset. Still, it's not as handy compared to MyModel.snippet_viewset, though.

Or introduce another method, e.g.

def get_snippet_viewset(model):
    return get_snippet_models()[model]

[gasman]

All looks good to me! Will leave this unmerged in case you want to do the changes proposed in #10235 (comment) as part of this PR.

[laymonage]

Merged in 8d2b1c6.