Refactor notification system to use action hooks instead

[pfefferle]

Deprecates the Notification class in favor of new activitypub_handled_{type} action hooks for all activity types. Updates all handler classes to trigger these hooks with consistent parameters, removes Notification usage, and updates integration and tests accordingly. This change improves extensibility and standardizes activity handling throughout the codebase.

For the context: #2216 (comment)

Proposed changes:

• Replace Notification usage with action hooks carrying consistent parameters (activity, user_id, state, context)
• Update handlers (Accept, Reject, Follow, Move, Create, Delete, Like, Update, Undo) to fire new hooks; adjust signatures to accept $user_id
• Update Stream_Connector to listen to activitypub_handled_follow and log accordingly; adjust tests to new method signatures

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

• See unittests

Changelog entry

• Automatically create a changelog entry from the details below.

Changelog Entry Details

Significance

• Patch
• Minor
• Major

Type

• Added - for new features
• Changed - for changes in existing functionality
• Deprecated - for soon-to-be removed features
• Removed - for now removed features
• Fixed - for any bug fixes
• Security - in case of vulnerabilities

Message

Standardized notification handling with new hooks for better extensibility and consistency.

[Copilot]

Pull Request Overview

Refactor to deprecate the Notification class and standardize activity handling via new activitypub_handled_{type} hooks across handlers and integrations, improving extensibility and consistency.

• Replace Notification usage with action hooks carrying consistent parameters (activity, user_id, state, context)
• Update handlers (Accept, Reject, Follow, Move, Create, Delete, Like, Update, Undo) to fire new hooks; adjust signatures to accept $user_id
• Update Stream_Connector to listen to activitypub_handled_follow and log accordingly; adjust tests to new method signatures

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
includes/class-notification.php	Mark Notification as deprecated and forward old hooks via do_action_deprecated to activitypub_handled_{type}.
includes/handler/class-follow.php	Emit activitypub_handled_follow and update queue_accept signature; remove Notification usage.
includes/handler/class-accept.php	Emit activitypub_handled_accept; remove Notification usage.
includes/handler/class-reject.php	Emit activitypub_handled_reject; remove Notification usage.
includes/handler/class-move.php	Accept $user_id and emit activitypub_handled_move with status and context.
includes/handler/class-update.php	Accept $user_id, split Update handling and emit activitypub_handled_update with state/reaction or actor context.
includes/handler/class-delete.php	Accept $user_id, track state, and emit activitypub_handled_delete; return state from maybe_delete_follower.
includes/handler/class-like.php	Normalize hook doc and use \do_action.
includes/handler/class-announce.php	Normalize hook doc and use \do_action.
includes/handler/class-undo.php	Add null context param to activitypub_handled_undo.
includes/handler/class-inbox.php	Update handled_inbox hook doc to new parameter semantics.
integration/class-stream-connector.php	Listen to activitypub_handled_follow; add new callback mapping and adapt logging payload.
tests/includes/handler/class-test-*.php	Update tests to new handler signatures (additional user_id parameter, queue_accept changes).

Comments suppressed due to low confidence (1)

includes/handler/class-delete.php:128

• Initialize $state to null at the beginning of the method to make control flow explicit and avoid relying on null coalescing with an undefined variable. For example: $state = null; … return $state;

		$follower = Remote_Actors::get_by_uri( $activity['actor'] );

		// Verify that Actor is deleted.
		if ( ! is_wp_error( $follower ) && Tombstone::exists( $activity['actor'] ) ) {
			$state = Remote_Actors::delete( $follower->ID );
			self::maybe_delete_interactions( $activity );
		}

		return $state ?? null;
	}

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[obenland]

One more thing I noticed was that we don't bail as much anymore and pass through WP_Errors to these hooks.

Hook naming (*_handled_*) and the way they executed up until now suggest that there's a reasonable expectation of success when they run. Like, the only reason these hooks would receive null or WP_Errors would be because there was some internal failure while handling a request.

I don't think we need to make these too generally applicable, that's what I'd consider activitypub_inbox_{type} hooks to be for. activitypub_handled_ hooks should probably be more something to use if you want to do something in response to something the plugin did.

[Copilot]

Pull Request Overview

Copilot reviewed 27 out of 27 changed files in this pull request and generated 2 comments.

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