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api - how to find out if a contact has addon XY installed

2025-05-19 16:18:52

Hubzilla Support Forum

adminsforum@hubzilla.org

oj wrote the following post Mon, 19 May 2025 16:18:52 +0200

api - how to find out if a contact has addon XY installed

Example:

User A has addon X installed.
User A and user B are connected (friends).

User A want's do find out if user B has the addon X installed as well. More precise: the PHP of the addon on the server of A wants to request the profile information of user B from the server of user B.

Is there an api endpoint that provides structured information about the profile, something like https://hub.org/profile/b/details

show all 12 comments

2025-05-19 17:03:24

od@zotum.net

@Hubzilla Support Forum
What is user B does not want to share the information?
Who has priority?

2025-05-19 17:38:30

oj@isar.digitalesparadies.de

What is user B does not want to share the information?

The observer A is known to the server of B.
This way server B can decide what information to give. This is the same mechanism as with cloud files for example.

2025-05-20 10:42:32

oj@isar.digitalesparadies.de

Any ideas? There are pages like https://hubzilla.org/help/developer/api_zot but I could find no call that would reveal the addons installed by a contact.

Before the addon is calling somehing like https://hub.org/flashcards/b/list it should probe the server of the contact what addons are activated by B. Otherwise the addon would produces error responses.

2025-05-20 13:02:48

Der Pepe (Hubzilla) ⁂ ⚝

pepecyb@hub.hubzilla.hu

In my opinion, this only makes sense if one add-on requires the installation of another add-on. I don't think it's a good idea to create add-ons that contain dependencies on other (optional) add-ons.

BTW: I am not aware of any API function that checks for the presence of an add-on.

2025-05-20 13:08:04

Harald Eilertsen

harald@hub.volse.no

@oj I don't think there is one. It could be added, but should probably be subject to some permission setting. E.g. "Can read my addon list", or something.

Another option for this specific case could be that the flashcards addon adds another permission, "Can access my flashcards", for example. And only tries to probe that if the remote contact has that permission defined and enabled. (Not sure how permissions are communicated across sites/channels, though, so there may be dragons...)

2025-05-20 13:48:35

Scott M. Stolz

scott@loves.tech

You may also want to have a way for addon developers to indicate if their app is supposed to be discoverable or not.

Some add-ons don't need to be discoverable or it would be undesirable for it to be discoverable.

2025-05-21 00:00:39

tombeau

tombeau@ein-hub-von-vielen.de

@Der Pepe (Hubzilla)

add-on requires the installation of another add-on

It is the same addon. The addon Flashcards of user A on server X wants to discover if his contact user B on server Y has the addon installed or not. If yes the communicate with each other to share boxes of flashcards, to synchronize changes,...

@Harald Eilertsen

"Can access my flashcards"

That is how it was a while ago. Now it uses the permission on cloud files. I tried to simplify the addon with the new version and to concentrate on the real purpose and throw every other stuff away - KISS.

Not sure how permissions are communicated across sites/channels,

But even if this is communicated: How to find out if it is used by an addon / if the addon is installed by the user?

@Scott M. Stolz

You may also want to have a way for addon developers to indicate if their app is supposed to be discoverable or not.

Yes, discoverable AND installed. That should solve the thing.

@Mike Macgirvin 🖥️ just suggested (in another thread) to probe the api endpoint and see how the server response is, 404 or example. That's how the addon does it at the moment. Elegant...???

Should I create an "issue" on Framagit?

On the sharing...

- Boxes are discoverable and shared between direct contacts only.
- Only the creator can set the license to "public domain". If set, a contact of a contact of a contact,... will see the box, but only if every of the contacts in the chain imported the box from its direct contact.
- Changes of the box will go the same way.
- Still, a user can set permissions on the JSON file (cloud file) that represents a box, via the app "Files". The addon uses (and respects) these permissions.

2025-05-21 00:04:13

tombeau

tombeau@ein-hub-von-vielen.de

mixed up my accounts, oj and tombeau is the same person :-(

2025-05-21 01:14:00

Scott M. Stolz

scott@loves.tech

@tombeau

But even if this is communicated: How to find out if it is used by an addon / if the addon is installed by the user?

The addon itself can create an endpoint that can be checked.

Basically, check a certain URL that is only used by that addon, and that addon could report back whether they are activated or not. If it does not report back, then you assume it is disabled or not installed.

2025-05-21 10:42:34

tombeau

tombeau@ein-hub-von-vielen.de

The addon itself can create an endpoint that can be checked.

That's how it is implemented at different places, examples: here or here. And this is what @Mike Macgirvin 🖥️ proposed for the moment.

I should have made this more clear, sorry.

My question is how a PHP code like $x = z_fetch_url(zid($url), false, $recurse, ['session' => true]); can discover if a contact on another server has the addon installed to avoid producting and dealing with 404 or other error responses, see links above. And ONLY if the same addon (example Flashcards) is installed by the contact, the api endpoint of the addon is requested. I hope this made it more clear now.

Of course the addon could implement something like

1. Discover if a contact has the addon installed by sending requests that result in error responses yes/no
2. Store the result in the database or in a cloud file, or at least in the local storage of the web browser, or...
3. Repeat the discovery from time to time to make sure if the user installed the addon in the meantime or not.

This is something I would avoid. This blows up the code and does not tackle the root cause of the problem. That's why I kept asking.

2025-05-21 11:07:09

Mario Vavti

mario@hub.somaton.com

@oj in the profile we disclose enabled protocol info. I think in the long term we could add a section where enabled addon apps are disclosed. That would have to be opt in per app with a setting in the apps settings page.

2025-05-21 15:51:43

oj@isar.digitalesparadies.de

Perfect!

in the profile we disclose enabled protocol info

Could you specify the URL to use to fetch the info. I would pock around a bit...