How does context in relation to django-components work?

[timothyis]

When using a component_block and filling a slot with HTML in a template, if I use a {{ variable }} within that slot, but use only on the block definition, the variable then doesn't fill.

I assume that this is because then the component_block doesn't have the context of the template within the slot. But this feels like it should be possible. I wonder if this is a limitation of the framework, rather than the package?

I really like enforcing the context that the component receives with parameters, but when it's a slot, it feels as if that's part of the template the block is placed in and should have the context, even when using only?

[EmilStenstrom]

@timothyis Thanks for the bug (I think) report. Could you show some sample code of how you use "only"? I don't think we have any tests related to the usage of only, so it's no surprise that this doesn't work as expected.

[timothyis]

Please don't stress over it too much though, I just thought I'd bring it up since you mentioned in my other issue that you'd like to support common use0cases and I though this was an interesting paradigm of usage that I feel front-end devs like myself are used to from React. But I do understand that this isn't React, so not everything will be like that 😅

[EmilStenstrom]

I still confused as to the use-case I think. In the example code you posted, what is the point of using only there? What context are you trying to avoic leaking into the component, and what context are you looking to allow inside it?

[timothyis]

Apologies for the late reply. What I'm trying to say is that I don't want the component internals to have access to the context of the page, but I do want the slots that I'm filling to have access to the context. At the moment it's one or the other.

{% component_block "menu" only %}
    {% slot "items" %}
        Logout {{ username }}
    {% endslot %}
{% end_component_block %}

Taking this as an example, the component itself (the code in the component files) will have access to the context if only is omitted here, but so will whatever I'm filling the slots with when I'm using the components on a page.

What I think would be good is if the items slot is still able to access the page context but the component itself aren't able to access the context.

Since the slot is being filled on the page, maybe it makes sense to allow the slow to have access to the page context, if only is there?

I'm not quite sure how context works and the reasons for it though, so maybe I'm off base here. However, I have very generic components that I can't create props like "username" for, since they might not be used anywhere else.

[EmilStenstrom]

I think we have a different idea of what only should be for. It's taken from the built-in include tag. The idea with that one is so that everything inside that include should only have access to the the specific variables sent to it, not anything else. So it's creating an unpassable boundary between this tag and anything outside it. Allowing username to pass through to the slots would break that boundary. So I simply think I don't agree with what only should do in this context.

[timothyis]

Yeah, makes sense. I really don't know a lot about Python/Django so I'm just spewing ideas that may help the project since it's made Django 1000% more enjoyable to use when coming from React.

[JuroOravec]

For anyone who comes across this thread, this has now been revamped in v0.70 (preferably use v0.72 or higher)

We now support both of the approaches above, as described by @timothyis and @EmilStenstrom.

For @timothyis's approach, in Django settings, set:

COMPONENTS = {
	"context_behavior": "isolated",
}

For @EmilStenstrom's approach, in Django settings, set:

COMPONENTS = {
	"context_behavior": "django",
}

For more info, see https://github.com/EmilStenstrom/django-components/blob/085c60a8c96442d9fd4f72d66a7eb295e7cfb2d9/README.md#context-behavior