Section 6 on C2S does not describe side effects of Accept or Reject

[trwnh]

This came up in issue triage a few weeks ago but we seem to have forgotten to capture it? (I can't find a related issue, at least.)

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S2S Accept describes receiving an Accept Follow in your inbox, which should add the actor to your following collection. But there is no language in C2S that describes Accept, or specifically that sending an Accept Follow should add that inner actor to your followers collection.

Likewise, S2S Reject describes how receiving a Reject Follow in your inbox MUST NOT result in adding that actor to your following collection, but there is no language in C2S that describes Reject, or specifically that sending a Reject Follow MUST NOT add that inner actor to your followers collection.

[evanp]

Yes, I think it was an oversight to leave out Accept and Reject from the API section of the specification. IIRC, we originally expected that Follow would be a single activity, not requiring acceptance or rejection, and then added it due to implementation feedback. Since many implementers were using the protocol but not the API, I think we just added it to the server-to-server section.

I think if we are open to adding longer errata, it would make sense to add two subsections for Accept and Reject in section 6. If not, we should plan to expand this in the next version of ActivityPub.

[evanp]

We have primer pages about Accept and Reject here:

• https://www.w3.org/wiki/ActivityPub/Primer/Accept_activity
• https://www.w3.org/wiki/ActivityPub/Primer/Reject_activity

[evanp]

During issue triage, we added errata to create two new subsections in section 6, one for each of Accept and Reject. They are based on the recommendations in the Primer, but only cover the normative requirements on the server.

https://www.w3.org/wiki/ActivityPub_errata/Proposed

[evanp]

The text, for clarity:

• In section 6 "Client to Server Interactions", a section should be inserted after section 6.5 "Follow activity" with the title "Accept activity" and the text: Upon receipt of an Accept activity into the outbox, if the object is an activity of type Follow, and the object of the Follow activity is not already in the actor's followers collection, and the Follow activity has not been undone by an Undo activity, then the server should add the actor of the Follow activity to the followers collection of the actor of the Accept activity.
• In section 6 "Client to Server Interactions", a section should be inserted after section 6.5 "Follow activity" with the title "Reject activity" and the text: Upon receipt of a Reject activity into the outbox, if the object of the activity exists, and the object is an activity of type Follow, and the object of the Follow activity is not already in the actor's followers collection, and the Follow activity has not been undone by an Undo activity, then the Follow activity is rejected, and the actor of the Follow activity is not added to the followers collection.