fix: implement MSC3959/3960/3961 extension room scoping and required_state delta #1450

0xnim · 2026-02-25T01:06:08Z

0xnim commented

2026-02-25 01:06:08 +00:00

This pull request fixes several spec-compliance gaps in the Simplified Sliding Sync (MSC4186) extension handling.

Receipts (MSC3960), typing (MSC3961), and per-room account data (MSC3959) were all being sent for every room regardless of their enabled flag or lists/rooms filter fields. These are now correctly scoped using a shared extension_room_set helper.

Additionally, required_state on incremental syncs now only sends state events that have changed since they were last delivered, and skips the DB lookup entirely when no state is requested and nothing else has changed.

Pull request checklist:

This pull request targets the main branch, and the branch is named something other than
main.
I have written an appropriate pull request title and my description is clear.
I understand I am responsible for the contents of this pull request.
I have followed the contributing guidelines:
- My contribution follows the code style, if applicable.
- I ran pre-commit checks before opening/drafting this pull request.
- I have tested my contribution (or proof-read it for documentation-only changes)
  myself, if applicable. This includes ensuring code compiles.
- My commit messages follow the commit message format and are descriptive.
- I have written a news fragment for this PR, if applicable.

This pull request fixes several spec-compliance gaps in the Simplified Sliding Sync (MSC4186) extension handling. Receipts (MSC3960), typing (MSC3961), and per-room account data (MSC3959) were all being sent for every room regardless of their enabled flag or lists/rooms filter fields. These are now correctly scoped using a shared extension_room_set helper. Additionally, required_state on incremental syncs now only sends state events that have changed since they were last delivered, and skips the DB lookup entirely when no state is requested and nothing else has changed.     **Pull request checklist:**  - [X] This pull request targets the `main` branch, and the branch is named something other than `main`. - [X] I have written an appropriate pull request title and my description is clear. - [X] I understand I am responsible for the contents of this pull request. - I have followed the [contributing guidelines][c1]: - [X] My contribution follows the [code style][c2], if applicable. - [X] I ran [pre-commit checks][c1pc] before opening/drafting this pull request. - [X] I have [tested my contribution][c1t] (or proof-read it for documentation-only changes) myself, if applicable. This includes ensuring code compiles. - [X] My commit messages follow the [commit message format][c1cm] and are descriptive. - [X] I have written a [news fragment][n1] for this PR, if applicable.  [c1]: https://forgejo.ellis.link/continuwuation/continuwuity/src/branch/main/CONTRIBUTING.md [c2]: https://forgejo.ellis.link/continuwuation/continuwuity/src/branch/main/docs/development/code_style.mdx [c1pc]: https://forgejo.ellis.link/continuwuation/continuwuity/src/branch/main/CONTRIBUTING.md#pre-commit-checks [c1t]: https://forgejo.ellis.link/continuwuation/continuwuity/src/branch/main/CONTRIBUTING.md#running-tests-locally [c1cm]: https://forgejo.ellis.link/continuwuation/continuwuity/src/branch/main/CONTRIBUTING.md#commit-messages [n1]: https://towncrier.readthedocs.io/en/stable/tutorial.html#creating-news-fragments

👍 1 ❤️ 2

0xnim added 10 commits

2026-02-25 01:06:08 +00:00

fix(sync): combine duplicate timeline PDU iterations 573bc731f9

fix(sync): remove dead return type from handle_lists 23e86e9e03

handle_lists always returned BTreeMap::default() and the call site
never captured the return value.

fix(sync): remove unused services parameter from collect_receipts 379fd097d1

The parameter was unused and suppressed with an underscore prefix.
Also replace explicit empty struct construction with Default::default().

fix(sync): avoid recomputing snake_key on each iteration in handle_lists 93b7aa6a34

The key is derived from sender_user, sender_device, and conn_id, all of
which are constant across list iterations. Compute it once before the loop.

fix(sync): include required_state in incremental room skip condition 7a5af75347

Rooms with pending required state events were incorrectly skipped on
incremental syncs when the timeline and receipts were empty. Move
collect_required_state before the early-continue and add its emptiness
as a guard condition.

fix(sync): restore _services param, add required_state skip, track room provenance 614a1a28a0

- Restore `_services: &Services` parameter on `collect_receipts`
- Add cheap pre-guard in `process_rooms` to skip `collect_required_state`
  DB call when no state was requested and there is nothing else to send
- `handle_lists` now returns `BTreeMap<String, BTreeSet<OwnedRoomId>>`
  (rooms visible per list window)
- `fetch_subscriptions` now returns `BTreeSet<OwnedRoomId>` (subscription
  rooms); captured as `_rooms_by_list` / `_subscription_rooms` for use
  in the upcoming extension-scoping changes

feat(sync): implement MSC3959/3960/3961 extension room scoping 7634dd826e

Add extension_room_set helper that computes the qualifying room set for
an extension from its lists and rooms filter fields per MSC4186.

MSC3960 receipts: move collection out of process_rooms into
collect_receipts, gated on enabled + filters.

MSC3961 typing: replace the dead filter variables in collect_typing_events
with an extension_room_set call so only qualifying rooms get typing data.

MSC3959 account data: move per-room collection out of process_rooms into
collect_account_data using per-room roomsince values and filter.

Route handler: collect_receipts and collect_account_data now run after
todo_rooms is populated; e2ee and to_device still run in parallel join.

feat(sync): track sent required_state per room for incremental sync delta d793d442ec

Add SnakeSyncCache.sent_state: a per-room map of (event_type, state_key)
→ event_id recording which state events were last sent to the client.

Two new Service methods:
  get_room_sent_state  – read the cache for one room
  update_room_sent_state – write the cache after each sync response

collect_required_state gains snake_key (None = connectionless/no cache)
and roomsince parameters:
  - roomsince == 0 (initial sync): return all matching events and
    populate the cache.
  - roomsince != 0 and snake_key is Some (incremental, has connection):
    only return events whose event_id differs from the cached value.
  - roomsince != 0 and snake_key is None (connectionless incremental):
    return all matching events (no cache to diff against).

Also export SnakeConnectionsKey from conduwuit-service::sync so the API
crate can reference it without duplicating the type definition.

chore: add news fragment for v5 sync extension scoping fixes 78f96806ee

style: cargo +nightly fmt

Documentation / Build and Deploy Documentation (pull_request) Has been skipped

Details

Checks / Prek / Pre-commit & Formatting (pull_request) Successful in 1m24s

Details

Checks / Prek / Clippy and Cargo Tests (pull_request) Successful in 27m22s

Details

5e33b29efc

0xnim commented

2026-02-25 01:07:09 +00:00

note for reviewers, commits are well seperated, might be easier to review one by one, then wholly

Jade commented

2026-02-25 01:13:23 +00:00

Yay! This is something I wanted to do since I was implementing typing indicators. Let me have a preliminary read

nex

2026-02-25 01:13:48 +00:00

added the
Enhancement

Matrix/Client

Matrix/MSC
labels
requested review from nex

nex added this to the next milestone

2026-02-25 01:14:03 +00:00

Jade requested review from Jade

2026-02-25 01:22:28 +00:00

Jade commented

2026-02-25 01:24:57 +00:00

I'm seeing a lot of good stuff here, will finish reviewing after I've slept

Jade approved these changes

2026-02-25 17:10:36 +00:00

Jade left a comment

Code level review, I think this is really good

src/api/client/sync/v5.rs

					
				@ -172,3 +165,2 @@

						typing: sync_events::v5::response::Typing::default(),

					};

					let (e2ee, to_device) = try_join(e2ee, to_device).await?;

I'm not sure building the response early and then filling in the default fields is the best idea?
It might be better to actually build it near the bottom.

I'm not sure building the response early and then filling in the default fields is the best idea? It might be better to actually build it near the bottom.

src/api/client/sync/v5.rs

					
				@ -171,3 +165,1 @@

						receipts,

						typing: sync_events::v5::response::Typing::default(),

					};

					let (e2ee, to_device) = try_join(e2ee, to_device).await?;

I don't think this needs to be awaited before the room-dependant fields.

I would kind of try plot a dependency graph here - we can start this before gathering rooms, but we don't need to finish it before building the response.
I think the room dependant ones should probably be shoved into their own future so they can be awaited in parallel (and happen in parallel within that)? Alternatively non-deoendant ones can be spawned in a task so they're active before an await.
That might require a bit of a restructure though.

I don't think this needs to be awaited before the room-dependant fields. I would kind of try plot a dependency graph here - we can start this before gathering rooms, but we don't need to finish it before building the response. I think the room dependant ones should probably be shoved into their own future so they can be awaited in parallel (and happen in parallel within that)? Alternatively non-deoendant ones can be spawned in a task so they're active before an await. That might require a bit of a restructure though.

Jade commented

2026-02-25 17:15:12 +00:00

I haven't checked if this handles the per-extension lists and rooms filters, but that was the other thing I wanted to fix. I'm not sure if anything actually uses it, though