fix(ogc): treat a ".." endpoint in a date range as an open bound

NEWS.md

@@ -1,3 +1,5 @@
+**10/07/2026:** **Bug fix:** a `".."` endpoint in a two-value date range -- `time=["2024-01-01", ".."]`, the open-ended form shown in the `waterdata.get_ratings()` docstring -- discarded the whole range, because `..` was not recognized as an open bound and failed to parse as a date. `waterdata.get_ratings()` then searched with no `datetime` at all and returned every rating regardless of date (59 instead of 44 for the docstring's bounding box from 2026-09-20 on), and the OGC getters (`get_daily()`, `get_continuous()`, `get_field_measurements()`, and the other `time`, `begin`, `end`, and `last_modified` arguments) sent an empty `time=` that the service rejected with HTTP 400 "Invalid datetime format". `".."` is now an open bound like `None`, so `["2024-01-01", ".."]` sends the same range as `"2024-01-01/.."` and `["2024-01-01", None]`.
+
 **10/03/2026:** `waterdata.get_field_measurements()` and
 `waterdata.get_field_measurements_metadata()` accept `sublocation_identifier`, a
 field USGS added to the `field-measurements` and `field-measurements-metadata`

dataretrieval/ogc/dates.py

@@ -61,15 +61,23 @@ def _parse_datetime(value: str) -> datetime | None:
     return None
 
 
+# The OGC API spelling of an open interval bound, as in ``"2024-01-01/.."``.
+_OPEN_BOUND = ".."
+
+
 def _is_blank(dt: str | None) -> bool:
-    """True for a None, NaN, or empty-string element."""
-    return dt is None or bool(pd.isna(dt)) or dt == ""
+    """True for a None, NaN, empty-string, or ``..`` element.
+
+    Each is a spelling of an open bound, so ``["2024-01-01", ".."]`` means the
+    same range as ``["2024-01-01", None]`` and the string ``"2024-01-01/.."``.
+    """
+    return dt is None or bool(pd.isna(dt)) or dt in ("", _OPEN_BOUND)
 
 
 def _format_one(dt: str | None, *, date: bool) -> str | None:
     """Format a single datetime element for inclusion in the API time arg."""
     if dt is None or _is_blank(dt):
-        return ".."
+        return _OPEN_BOUND
     parsed = _parse_datetime(dt)
     if parsed is None:
         return None
@@ -104,7 +112,7 @@ def _is_passthrough(single: str) -> bool:
 
 
 def _all_blank(items: list[str | None]) -> bool:
-    """True when every element is None, NaN, or the empty string."""
+    """True when every element is None, NaN, the empty string, or ``..``."""
     return all(_is_blank(dt) for dt in items)
 
 
@@ -127,8 +135,8 @@ def _format_api_dates(
         A single date/datetime string or a list of one or two date/datetime
         strings. Accepts formats like "%Y-%m-%d %H:%M:%S", ISO 8601 (with or
         without ``Z``/numeric offset), or relative periods (e.g., "P7D" /
-        "PT36H"). Range endpoints may be ``None``/``NaN``/empty to denote a
-        half-bounded range.
+        "PT36H"). Range endpoints may be ``None``/``NaN``/empty or ``".."``
+        to denote a half-bounded range.
     date : bool, optional
         If True, uses only the date portion ("YYYY-MM-DD"). If False (default),
         returns full datetime in UTC ISO 8601 format ("YYYY-MM-DDTHH:MM:SSZ").
@@ -162,9 +170,9 @@ def _format_api_dates(
     Notes
     -----
     - A single blank/NA value returns None. In a two-value range, a blank/NA
-      endpoint is rendered as ``".."`` to denote an open bound (e.g.
-      ``"2024-01-01/.."``); the range is only None when *every* element is
-      blank/NA or any non-NA element fails to parse.
+      or ``".."`` endpoint is rendered as ``".."`` to denote an open bound
+      (e.g. ``"2024-01-01/.."``); the range is only None when *every* element
+      is blank/NA/``".."`` or any other element fails to parse.
     - Supports ISO 8601 durations such as "P7D" and "PT36H" and pre-formatted
       intervals containing ``"/"``; both are passed through unchanged.
     - Converts datetimes to UTC and formats as ISO 8601 with 'Z' suffix when

tests/waterdata_ratings_test.py

@@ -169,6 +169,27 @@ def test_get_ratings_download_and_parse_false_returns_features(httpx_mock):
     assert features[0]["id"] == "USGS-01104475.exsa.rdb"
 
 
+def test_get_ratings_keeps_a_dotdot_open_bound_in_time(httpx_mock):
+    """``time=[start, ".."]`` is the documented open-ended range. The ``..``
+    endpoint used to fail to parse, which discarded the whole range, so the
+    search went out with no ``datetime`` and returned every rating."""
+    httpx_mock.add_response(
+        method="GET",
+        url=STAC_SEARCH_RE,
+        json=_stub_search_response(),
+    )
+    get_ratings(
+        monitoring_location_id="USGS-01104475",
+        # A UTC instant, so the expected bound does not depend on the local zone
+        # a naive date is read in.
+        time=["2026-04-29T00:00:00Z", ".."],
+        download_and_parse=False,
+    )
+    (request,) = httpx_mock.get_requests()
+    params = parse_qs(urlsplit(str(request.url)).query)
+    assert params["datetime"] == ["2026-04-29T00:00:00Z/.."]
+
+
 def test_get_ratings_multi_type_filters_via_property(httpx_mock, tmp_path):
     """File_type list: server filter omits it; local filter reads the property."""
     httpx_mock.add_response(

tests/waterdata_test.py

@@ -784,6 +784,22 @@ def test_get_daily(httpx_mock):
     assert hasattr(md, "url") and hasattr(md, "query_time")
 
 
+def test_get_daily_keeps_a_dotdot_open_bound_in_time(httpx_mock):
+    """A ``..`` endpoint in a ``time`` list is an open bound, as in the string
+    form ``"2025-01-01/.."``. It used to discard the whole range and send an
+    empty ``time=``, which the service rejects as an invalid datetime."""
+    _mock_items(httpx_mock, "daily")
+
+    get_daily(
+        monitoring_location_id="USGS-05427718",
+        parameter_code="00060",
+        time=["2025-01-01", ".."],
+    )
+
+    (sent,) = _sent(httpx_mock, "daily")
+    assert sent["time"] == ["2025-01-01/.."]
+
+
 def test_get_daily_value_is_float_when_every_value_is_whole(httpx_mock):
     """Issue #428: whole-number values used to infer ``int64``, so ``value``
     changed dtype between calls. It is ``float64`` regardless of the data."""

tests/waterdata_utils_test.py

@@ -936,6 +936,13 @@ def test_type_cols_warning_is_singular_for_one_value():
         ("2024-01-01 00:00:00", True, "2024-01-01"),
         (["2024-01-01", None], True, "2024-01-01/.."),
         ([None, "2024-01-01"], True, "../2024-01-01"),
+        (["2024-01-01", ".."], True, "2024-01-01/.."),
+        (["..", "2024-01-01"], True, "../2024-01-01"),
+        (
+            ["2018-02-12T23:20:50Z", ".."],
+            False,
+            "2018-02-12T23:20:50Z/..",
+        ),
     ],
     ids=[
         "iso8601_z",
@@ -951,6 +958,9 @@ def test_type_cols_warning_is_singular_for_one_value():
         "space_separated",
         "open_ended_none_end",
         "open_ended_none_start",
+        "open_ended_dotdot_end",
+        "open_ended_dotdot_start",
+        "open_ended_dotdot_datetime",
     ],
 )
 def test_format_api_dates(value, date, expected):
@@ -971,6 +981,7 @@ def test_format_api_dates_treats_an_all_blank_sequence_as_no_filter():
     all -- sending ``../..`` would be a query the service has to reject."""
     assert _format_api_dates([None, None]) is None
     assert _format_api_dates(["", ""]) is None
+    assert _format_api_dates(["..", ".."]) is None
 
 
 def test_format_api_dates_rejects_more_than_two_values():