fix(routes): clearing observers in the edit modal now persists

[jinglemansweep]

What

Fixes a bug where removing all observers in the Route edit modal silently failed — the PUT returned 200, but the observers came back on next page load.

Root cause

src/meshcore_hub/web/static/js/spa/pages/routes.js:812 built the PUT body with a ternary that collapsed an empty observer list to null:

observer_public_keys: observerPublicKeys.length > 0 ? observerPublicKeys : null,

On the backend, Pydantic parsed null as None, and the PUT handler's guard at api/routes/routes.py:589 skipped the sync:

if body.observer_public_keys is not None:
    observer_nodes = _resolve_nodes_by_pubkey(session, body.observer_public_keys)
    _sync_observers(session, route, observer_nodes)

So:

• Add observers → array → guard passes → _sync_observers deletes + recreates → worked.
• Clear observers → null → guard failed → _sync_observers skipped → DB unchanged.

The None-means-skip semantic is correct for partial PATCH-style updates, so the bug is purely on the frontend: the route modal is a full-form PUT (every field is sent every time), so it shouldn't use the "send null when empty" pattern.

Fix

One-line change in routes.js — always send the array:

// Before
observer_public_keys: observerPublicKeys.length > 0 ? observerPublicKeys : null,
// After
observer_public_keys: observerPublicKeys,

When empty, JS serializes [], Pydantic parses as [] (not None), the guard passes, and _sync_observers deletes every existing RouteObserver row.

Regression test

tests/test_api/test_routes.py — added test_update_clear_observers_with_empty_list next to the existing test_update_observers. It:

1. PUTs with one observer pubkey → asserts the response has 1 observer.
2. PUTs again with observer_public_keys: [] → asserts response route_observers is [].
3. GETs the detail endpoint to confirm persistence (catches any future "response lies but DB didn't update" regression).

This locks the contract so a future client (frontend or otherwise) can't silently reintroduce the bug by sending null for the empty case.

Scope (explicitly unchanged)

• RouteUpdate.observer_public_keys: Optional[list[str]] = None — the None-means-skip semantic stays; it's correct for true partial updates from other clients.
• _sync_observers (routes.py:158) — already does delete-all-then-recreate correctly.
• Create flow — null and [] are equivalent on create (both mean "all observers"), so the same line worked by accident when creating. No change needed.
• node_public_keys (line 811) — already sends the array unconditionally; no change.
• Preview endpoint — read-only.

Tests

pytest --no-cov tests/test_api/test_routes.py
# → 50 passed

pytest --no-cov   # full suite
# → 1461 passed, 22 skipped

pre-commit run --all-files → clean (black, flake8, mypy, hooks).

Manual verification

Build the stack, then in the running app:

1. Open /routes, edit a route, add an observer, save. Confirm it appears.
2. Re-edit the same route, click ✕ on the observer chip (so the chip list is empty), save.
3. Reload the page. Observer list is now empty.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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