Make _handle_stats_nesting tolerant of missing drop columns (#257)

Both `.drop()` calls in `_handle_stats_nesting` (for the geopandas and
pandas branches) hardcoded literal column names — `["type",
"properties.data"]` and `["data"]`. If a stats response is ever returned
in a slightly different shape (or one of those keys is renamed/removed),
`drop()` raises `KeyError` and aborts the helper. The sibling
`pd.json_normalize(...)` call later in the same function already passes
`errors="ignore"`, so add the same to the two `drop()` calls for parity.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: thodson-usgs

dataretrieval/waterdata/utils.py

@@ -892,11 +892,13 @@ def _handle_stats_nesting(
     # otherwise return a geodataframe
     if not geopd:
         df = pd.json_normalize(body["features"]).drop(
-            columns=["type", "properties.data"]
+            columns=["type", "properties.data"], errors="ignore"
         )
         df.columns = df.columns.str.split(".").str[-1]
     else:
-        df = gpd.GeoDataFrame.from_features(body["features"]).drop(columns=["data"])
+        df = gpd.GeoDataFrame.from_features(body["features"]).drop(
+            columns=["data"], errors="ignore"
+        )
 
     # Unnest json features, properties, data, and values while retaining necessary
     # metadata to merge with main dataframe.

tests/waterdata_utils_test.py

@@ -4,6 +4,7 @@
 
 from dataretrieval.waterdata.utils import (
     _get_args,
+    _handle_stats_nesting,
     _walk_pages,
 )
 
@@ -80,3 +81,33 @@ def test_walk_pages_multiple_mocked():
     assert mock_client.send.called
     assert mock_client.request.called
     assert mock_client.request.call_args[0][1] == "https://example.com/page2"
+
+
+def test_handle_stats_nesting_tolerates_missing_drop_columns():
+    """If the upstream stats response shape ever changes such that one of
+    the columns we try to drop ("type", "properties.data") is absent, the
+    function should still return a DataFrame instead of raising KeyError.
+    """
+    body = {
+        "next": None,
+        "features": [
+            {
+                "properties": {
+                    "monitoring_location_id": "USGS-12345",
+                    "data": [
+                        {
+                            "parameter_code": "00060",
+                            "unit_of_measure": "ft^3/s",
+                            "parent_time_series_id": "ts-1",
+                            "values": [{"statistic_id": "mean", "value": 10.0}],
+                        }
+                    ],
+                },
+            }
+        ],
+    }
+
+    df = _handle_stats_nesting(body, geopd=False)
+
+    assert len(df) == 1
+    assert df["monitoring_location_id"].iloc[0] == "USGS-12345"