0025. Built-in Adapter observation stays rooms-only

Status: Accepted · 2026-08-12 · #238 Governed by: 0000, 0008, 0013, 0018

TL;DR Smocket stabilizes the built-in adapter's live rooms map for observation. The other methods and events lack a core use and conflict with teardown or custom-adapter boundaries, so they stay outside the v1 compatibility surface.

Decision

Fresh Socket.IO 4.7.5 and 4.8.3 installs both resolved socket.io-adapter 2.5.8. Runtime probes found the same behavior in both: addAll processes a Set in insertion order, emits create-room before adding the first member, then emits join-room after adding it, and emits nothing for duplicate membership. Removal emits leave-room after removing the member and delete-room after removing an empty room key. During delAll, those pairs follow the socket's room insertion order while its sids entry remains intact until every room is removed. disconnecting precedes these removals and disconnect follows them.

socketRooms returns the same live Set while connected and undefined after teardown; sockets returns the sids present in both sids and the namespace socket roster for an empty Set, and a deduplicated room union otherwise. The declarations expose addAll as void | Promise<void>, delAll as void, socketRooms as Set | undefined, and sockets as Promise<Set>. The events inherit Node EventEmitter's untyped string-and-any[] surface, so their names and payloads are not encoded in the declarations.

Smocket keeps only namespace.adapter.rooms as built-in Adapter compatibility surface. Its live membership and removal of empty room keys are already needed to inspect routing state. External mutation of the map is not supported. Every new candidate is deferred:

Candidate	Decision	Reason
addAll, delAll	Defer	socket.join, socket.leave, and disconnect already own membership changes; direct mutation would add a second lifecycle entry point.
socketRooms	Defer	socket.rooms already supplies the application observation, and exact live-reference teardown conflicts with 0013.
sockets	Defer	Smocket's core already routes through its Smocket-only socketsIn; no application or extension use requires the upstream async lookup contract.
create-room, join-room, leave-room, delete-room	Defer	No concrete consumer requires them, while promising on would widen the separate SmocketAdapter registration contract or make namespace.adapter inconsistent after replacement.

The teardown conflict is observable. While connected, real socket.rooms is the same Set returned by adapter.socketRooms(id). After disconnect, the getter returns a new empty Set, but a reference captured before disconnect retains every old room. Decision 0013 instead requires that captured Smocket reference to be emptied in place. This decision does not silently reverse 0013; a future socketRooms proposal must first revisit it explicitly.

The exported Adapter and SmocketAdapter keep add, del, sids, socketsIn, and the optional scheduling hook as Smocket-only surface under 0008 and 0018. They remain incompatible with arbitrary Socket.IO adapters. Decision 0031 adds a narrow optional whole-socket removal signal for native extension cleanup without adding delAll, upstream lifecycle events, or another built-in observation promise. No deferred member blocks v1.

Alternatives rejected

• Accept every matching name before v1. Name parity alone does not justify eight new behavioral promises, including intermediate map state, reference identity, and event order.
• Accept only lookups and lifecycle events now. socketRooms still reaches the 0013 conflict, and events still change what every registered custom adapter must provide.
• Make SmocketAdapter match Socket.IO's Adapter. A real adapter also owns transport delivery and multi-server behavior that Smocket cannot reproduce; 0008 and 0018 already assign this seam a narrower routing and test-scheduling role.