Fix last imap message is not reset on empty search (#93119)

homeassistant/components/imap/coordinator.py

@@ -201,7 +201,9 @@ class ImapDataUpdateCoordinator(DataUpdateCoordinator[int | None]):
             raise UpdateFailed(
                 f"Invalid response for search '{self.config_entry.data[CONF_SEARCH]}': {result} / {lines[0]}"
             )
-        count: int = len(message_ids := lines[0].split())
+        if not (count := len(message_ids := lines[0].split())):
+            self._last_message_id = None
+            return 0
         last_message_id = (
             str(message_ids[-1:][0], encoding=self.config_entry.data[CONF_CHARSET])
             if count

tests/components/imap/test_init.py

@@ -15,6 +15,7 @@ from homeassistant.util.dt import utcnow
 
 from .const import (
     BAD_RESPONSE,
+    EMPTY_SEARCH_RESPONSE,
     TEST_FETCH_RESPONSE_BINARY,
     TEST_FETCH_RESPONSE_HTML,
     TEST_FETCH_RESPONSE_INVALID_DATE,
@@ -347,3 +348,101 @@ async def test_fetch_number_of_messages(
     # we should have an entity with an unavailable state
     assert state is not None
     assert state.state == STATE_UNAVAILABLE
+
+
+@pytest.mark.parametrize("imap_search", [TEST_SEARCH_RESPONSE])
+@pytest.mark.parametrize(
+    ("imap_fetch", "valid_date"),
+    [(TEST_FETCH_RESPONSE_TEXT_PLAIN, True)],
+    ids=["plain"],
+)
+@pytest.mark.parametrize("imap_has_capability", [True, False], ids=["push", "poll"])
+async def test_reset_last_message(
+    hass: HomeAssistant, mock_imap_protocol: MagicMock, valid_date: bool
+) -> None:
+    """Test receiving a message successfully."""
+    event = asyncio.Event()  # needed for pushed coordinator to make a new loop
+
+    async def _sleep_till_event() -> None:
+        """Simulate imap server waiting for pushes message and keep the push loop going.
+
+        Needed for pushed coordinator only.
+        """
+        nonlocal event
+        await event.wait()
+        event.clear()
+        mock_imap_protocol.idle_start.return_value = AsyncMock()()
+
+    # Make sure we make another cycle (needed for pushed coordinator)
+    mock_imap_protocol.idle_start.return_value = AsyncMock()()
+    # Mock we wait till we push an update (needed for pushed coordinator)
+    mock_imap_protocol.wait_server_push.side_effect = _sleep_till_event
+
+    event_called = async_capture_events(hass, "imap_content")
+
+    config_entry = MockConfigEntry(domain=DOMAIN, data=MOCK_CONFIG)
+    config_entry.add_to_hass(hass)
+    assert await hass.config_entries.async_setup(config_entry.entry_id)
+    await hass.async_block_till_done()
+    # Make sure we have had one update (when polling)
+    async_fire_time_changed(hass, utcnow() + timedelta(seconds=5))
+    await hass.async_block_till_done()
+    state = hass.states.get("sensor.imap_email_email_com")
+    # We should have received one message
+    assert state is not None
+    assert state.state == "1"
+
+    # We should have received one event
+    assert len(event_called) == 1
+    data: dict[str, Any] = event_called[0].data
+    assert data["server"] == "imap.server.com"
+    assert data["username"] == "email@email.com"
+    assert data["search"] == "UnSeen UnDeleted"
+    assert data["folder"] == "INBOX"
+    assert data["sender"] == "john.doe@example.com"
+    assert data["subject"] == "Test subject"
+    assert data["text"]
+    assert (
+        valid_date
+        and isinstance(data["date"], datetime)
+        or not valid_date
+        and data["date"] is None
+    )
+
+    # Simulate an update where no messages are found (needed for pushed coordinator)
+    mock_imap_protocol.search.return_value = Response(*EMPTY_SEARCH_RESPONSE)
+
+    # Make sure we have an update
+    async_fire_time_changed(hass, utcnow() + timedelta(seconds=30))
+
+    # Awake loop (needed for pushed coordinator)
+    event.set()
+
+    await hass.async_block_till_done()
+
+    state = hass.states.get("sensor.imap_email_email_com")
+    # We should have message
+    assert state is not None
+    assert state.state == "0"
+    # No new events should be called
+    assert len(event_called) == 1
+
+    # Simulate an update where with the original message
+    mock_imap_protocol.search.return_value = Response(*TEST_SEARCH_RESPONSE)
+    # Make sure we have an update again with the same UID
+    async_fire_time_changed(hass, utcnow() + timedelta(seconds=30))
+
+    # Awake loop (needed for pushed coordinator)
+    event.set()
+
+    await hass.async_block_till_done()
+
+    state = hass.states.get("sensor.imap_email_email_com")
+    # We should have received one message
+    assert state is not None
+    assert state.state == "1"
+    await hass.async_block_till_done()
+    await hass.async_block_till_done()
+
+    # One new event
+    assert len(event_called) == 2