feat: answer REQ with CLOSED when no relay is configured

Ported from the upstream PR (lnbits/nostrclient#74, idea from #68).
Nothing will ever serve a subscription when nostrclient has no relay
at all, so refuse it per NIP-01 instead of registering it silently.
Keyed on "no relay configured" rather than "none connected": a
configured relay that is merely reconnecting gets the cached
subscription replayed, so refusing the REQ there would be a regression.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Tbyw6FwjhEJg3gHfPHxWt

README.md

@@ -50,7 +50,7 @@ flowchart LR
 3. **Fan-Out** - Subscription requests are sent to all configured relays
 4. **Aggregation** - Events from all relays are collected and deduplicated
 5. **Response** - Events are sent back to the client with the original subscription ID
-6. **Publish Acknowledgement** - Every `EVENT` a client publishes gets exactly one `["OK", <id>, <accepted>, <message>]` reply (NIP-01): `true` as soon as any relay accepts it, `false` once every relay has rejected it, the wait times out (10 s), or no relay is connected
+6. **Publish Acknowledgement** - Every `EVENT` a client publishes gets exactly one `["OK", <id>, <accepted>, <message>]` reply (NIP-01): `true` as soon as any relay accepts it, `false` once every relay has rejected it, the wait times out (10 s), or no relay is connected. A `REQ` while no relay is configured at all is answered with `CLOSED`
 
 ## Configuration
 

router.py

@@ -195,7 +195,7 @@ class NostrRouter:
         assert len(json_data), "Bad JSON array"
 
         if json_data[0] == "REQ":
-            self._handle_client_req(json_data)
+            await self._handle_client_req(json_data)
             return
 
         if json_data[0] == "CLOSE":
@@ -223,15 +223,29 @@ class NostrRouter:
         self.pending_publishes[event_id] = PendingPublish(event_id, len(connected))
         nostr_client.relay_manager.publish_message(json_str)
 
-    def _handle_client_req(self, json_data):
+    async def _handle_client_req(self, json_data):
         subscription_id = json_data[1]
         logger.info(f"New subscription: '{subscription_id}'")
+        if not nostr_client.relay_manager.relays:
+            # NIP-01: nothing will ever serve this subscription, so refuse it.
+            # Only when no relay is configured at all: a configured relay that
+            # is merely reconnecting gets the cached subscription replayed.
+            await self._send_closed(subscription_id, "error: no relay connections")
+            return
         subscription_id_rewritten = urlsafe_short_hash()
         self.original_subscription_ids[subscription_id_rewritten] = subscription_id
         filters = json_data[2:]
 
         nostr_client.relay_manager.add_subscription(subscription_id_rewritten, filters)
 
+    async def _send_closed(self, subscription_id: str, message: str):
+        try:
+            await self.websocket.send_text(
+                json.dumps(["CLOSED", subscription_id, message])
+            )
+        except Exception as e:
+            logger.debug(f"Failed to send CLOSED for '{subscription_id}': {e}")
+
     def _handle_client_close(self, subscription_id):
         subscription_id_rewritten = next(
             (

tests/test_router_ok.py

@@ -25,10 +25,14 @@ class FakeRelayManager:
     def __init__(self, relays: dict[str, FakeRelay]):
         self.relays = relays
         self.published: list[str] = []
+        self.subscriptions: list[str] = []
 
     def publish_message(self, message: str):
         self.published.append(message)
 
+    def add_subscription(self, subscription_id: str, filters):
+        self.subscriptions.append(subscription_id)
+
     def close_subscriptions(self, subscriptions):
         pass
 
@@ -139,3 +143,25 @@ async def test_stop_drops_pending_publishes(monkeypatch):
 
     assert router.pending_publishes == {}
     assert NostrRouter.received_command_results == {}
+
+
+@pytest.mark.asyncio
+async def test_req_without_configured_relays_is_closed(monkeypatch):
+    router, ws, manager = _router(monkeypatch, {})
+
+    await router._handle_client_to_nostr(json.dumps(["REQ", "sub1", {"kinds": [1]}]))
+
+    assert ws.sent == [["CLOSED", "sub1", "error: no relay connections"]]
+    assert router.subscriptions == []
+    assert manager.subscriptions == []
+
+
+@pytest.mark.asyncio
+async def test_req_with_configured_but_disconnected_relay_is_kept(monkeypatch):
+    router, ws, manager = _router(monkeypatch, {"wss://a": FakeRelay(False)})
+
+    await router._handle_client_to_nostr(json.dumps(["REQ", "sub1", {"kinds": [1]}]))
+
+    assert ws.sent == []
+    assert len(router.subscriptions) == 1
+    assert len(manager.subscriptions) == 1