Fix imap sensor in case of alternative empty search response (#132081)

homeassistant/components/imap/coordinator.py

@@ -332,7 +332,17 @@ class ImapDataUpdateCoordinator(DataUpdateCoordinator[int | None]):
             raise UpdateFailed(
                 f"Invalid response for search '{self.config_entry.data[CONF_SEARCH]}': {result} / {lines[0]}"
             )
-        if not (count := len(message_ids := lines[0].split())):
+        # Check we do have returned items.
+        #
+        # In rare cases, when no UID's are returned,
+        # only the status line is returned, and not an empty line.
+        # See: https://github.com/home-assistant/core/issues/132042
+        #
+        # Strictly the RfC notes that 0 or more numbers should be returned
+        # delimited by a space.
+        #
+        # See: https://datatracker.ietf.org/doc/html/rfc3501#section-7.2.5
+        if len(lines) == 1 or not (count := len(message_ids := lines[0].split())):
             self._last_message_uid = None
             return 0
         last_message_uid = (

tests/components/imap/const.py

@@ -141,6 +141,8 @@ TEST_CONTENT_MULTIPART_BASE64_INVALID = (
 )
 
 EMPTY_SEARCH_RESPONSE = ("OK", [b"", b"Search completed (0.0001 + 0.000 secs)."])
+EMPTY_SEARCH_RESPONSE_ALT = ("OK", [b"Search completed (0.0001 + 0.000 secs)."])
+
 BAD_RESPONSE = ("BAD", [b"", b"Unexpected error"])
 
 TEST_SEARCH_RESPONSE = ("OK", [b"1", b"Search completed (0.0001 + 0.000 secs)."])

tests/components/imap/test_init.py

@@ -20,6 +20,7 @@ from homeassistant.util.dt import utcnow
 from .const import (
     BAD_RESPONSE,
     EMPTY_SEARCH_RESPONSE,
+    EMPTY_SEARCH_RESPONSE_ALT,
     TEST_BADLY_ENCODED_CONTENT,
     TEST_FETCH_RESPONSE_BINARY,
     TEST_FETCH_RESPONSE_HTML,
@@ -517,6 +518,11 @@ async def test_fetch_number_of_messages(
     assert state.state == STATE_UNAVAILABLE
 
 
+@pytest.mark.parametrize(
+    "empty_search_reponse",
+    [EMPTY_SEARCH_RESPONSE, EMPTY_SEARCH_RESPONSE_ALT],
+    ids=["regular_empty_search_response", "alt_empty_search_response"],
+)
 @pytest.mark.parametrize("imap_search", [TEST_SEARCH_RESPONSE])
 @pytest.mark.parametrize(
     ("imap_fetch", "valid_date"),
@@ -525,7 +531,10 @@ async def test_fetch_number_of_messages(
 )
 @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
+    hass: HomeAssistant,
+    mock_imap_protocol: MagicMock,
+    valid_date: bool,
+    empty_search_reponse: tuple[str, list[bytes]],
 ) -> None:
     """Test receiving a message successfully."""
     event = asyncio.Event()  # needed for pushed coordinator to make a new loop
@@ -580,7 +589,7 @@ async def test_reset_last_message(
     )
 
     # Simulate an update where no messages are found (needed for pushed coordinator)
-    mock_imap_protocol.search.return_value = Response(*EMPTY_SEARCH_RESPONSE)
+    mock_imap_protocol.search.return_value = Response(*empty_search_reponse)
 
     # Make sure we have an update
     async_fire_time_changed(hass, utcnow() + timedelta(seconds=30))