[Turbo] Add expression language to topics

[rskuipers]

Q	A
Bug fix?	no
New feature?	yes
Tickets
License	MIT

Why

With the current implementation of the Broadcast attribute there's no way to scope newly added entities. A newly added entity will be broadcasted to anywhere that uses turbo_stream_listen("App\\Entity\\Book"). But there are use-cases where you want to limit this.

For one, imagine having a template author/show.html.twig where you want to show all the books belonging to a specific author. A newly added Book entity would show up on all the author pages because there's no way to supply a scope to turbo_stream_listen.

Secondly, there's currently no way to limit access based on the logged in user. For simplicity's sake let's imagine every author belongs to a publisher. The publisher can login and add/edit/remove authors that belong to them. Now let's say we have a template called author/list.html.twig on which we use turbo_stream_listen("App\\Entity\\Author"). In the current implementation, this would also show all newly created Authors created by other Publishers.

So adding a scope is both useful for showing specific listings as well as listings that should only be shown to a specific user.

Adding expression language support to topics makes it possible to scope these topics based on a relationship or some other context.

How

We can achieve the above by changing two points in the code.

https://github.com/rskuipers/ux/blob/feature/add-scope-option-to-broadcast/src/Turbo/Tests/app/Entity/Book.php#L23

Expanding the Broadcast attribute with a scope option that supports Expression Language. This will be executed when an entity is created/changed typically in order to retrieve an ID of a parent entity that will function as a scope.

Note: this expression has null checking because the relationship is optional. Also in Expression Language 6.1 you can use the null-safe operator: entity.author?.id

https://github.com/rskuipers/ux/blob/feature/add-scope-option-to-broadcast/src/Turbo/Twig/TwigExtension.php#L44

Adding a third parameter $scope = null here so that you can provide a value used to add a scope to the topic you're listening to.

https://github.com/rskuipers/ux/blob/feature/add-scope-option-to-broadcast/src/Turbo/Twig/ScopedTurboStreamListenRendererInterface.php

Adding a separate interface with a method supporting a third parameter ?string $scope = null here so that this can be integrated into the topic to listen for a scoped topic.

[rskuipers]

This would obviously still need documentation, but I'm just awaiting confirmation before I start writing that.

[weaverryan]

A few questions - but I think the approach is solid.

@dunglas - what do you think about this idea? tl;dr

1. Optional scope option added using expression language - e.g. [Broadcast(scope: 'entity.author.id')]
2. This causes the topic to change to https://symfony.com/ux-turbo/App%5CEntity%5CBook_15/7 where 15 is the entity.author.id value and 7 is the main Book object's value that was just added/updated.

[dunglas]

Nice idea!

We have a similar feature in API Platform: https://github.com/api-platform/core/blob/main/src/Doctrine/EventListener/PublishMercureUpdatesListener.php#L225-L244

Basically, the idea is to let the user generate the whole topic using Expression Language. This has the benefit of giving full control to the user and to leverage all the capabilities of the underlying Transport.

What do you think about following this approach?

[rskuipers]

@dunglas That's brilliant! Looks like it will fit here as well, definitely adds even more flexibility and it solves the problem with the current implementation where it's limited to 1 scope.

If @weaverryan agrees then I'll go ahead and reimplement it using your suggestion.

[rskuipers]

I have updated this PR to the method suggested by @dunglas.

[weaverryan]

Minor comments - but this is just about ready for merge - thanks!

[weaverryan]

Friendly ping @rskuipers - I'm hoping to tag all of UX this week, it'd be great if this got in there :)

[rskuipers]

I'll make some time for it! No problem :)

…

On Tue, Jun 14, 2022, 19:17 Ryan Weaver ***@***.***> wrote: Friendly ping @rskuipers <https://github.com/rskuipers> - I'm hoping to tag all of UX this week, it'd be great if this got in there :) — Reply to this email directly, view it on GitHub <#327 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAOUMNQSRISJ427WYD6QKCDVPC5DLANCNFSM5XIR23JA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[rskuipers]

@weaverryan I've reverted the existing books test and created separate entities to test the expression language feature as advised by @dunglas. I've also made expression language optional and changed object to entity to be more in-line with the rest of the code. I've also added a small bit of documentation. Not sure if you want to dedicate an entire chapter to it or if this is enough.

[weaverryan]

Thank you Rick!