FIX: add_driver_ahead doesn't work with resampled telemetry (fixes #430)

docs/changelog/v3.1.x.rst

@@ -1,3 +1,17 @@
+What's new in v3.1.4
+--------------------
+
+(released ??/??/2023)
+
+Bug Fixes
+^^^^^^^^^
+
+- fixed a bug that caused :func:`~fastf1.core.Telemetry.add_driver_ahead` to
+  only work with telemetry data that matches the sampling timebase of the
+  car data (#430)
+
+
+
 What's new in v3.1.3
 --------------------
 

fastf1/core.py

@@ -812,10 +812,10 @@ def add_driver_ahead(self, drop_existing: bool = True) -> "Telemetry":
                          index=ref_tel.index)
         )
 
-        if ((d['SessionTime'].shape != dtd['SessionTime'].shape)
-                or np.any((d['SessionTime'].values
-                           != dtd['SessionTime'].values))):
-            dtd = dtd.resample_channels(new_date_ref=d["SessionTime"])
+        if ((d['Date'].shape != dtd['Date'].shape)
+                or np.any((d['Date'].values
+                           != dtd['Date'].values))):
+            dtd = dtd.resample_channels(new_date_ref=d["Date"])
 
         # indices need to match as .join works index-on-index
         dtd['_SelfIndex'] = d.index

fastf1/tests/test_telemetry.py

@@ -280,12 +280,22 @@ def test_resampling_up(reference_laps_data):
 
 
 @pytest.mark.f1telapi
-def test_add_driver_ahead(reference_laps_data):
+@pytest.mark.parametrize(
+    "resample_rule",
+    [None, "0.1S"]  # test base frequency and resampled
+)
+def test_add_driver_ahead(reference_laps_data, resample_rule):
     session, laps = reference_laps_data
     test_data = laps.pick_fastest().get_car_data()
+    if resample_rule is not None:
+        test_data = test_data.resample_channels(rule=resample_rule)
     test_data = test_data.add_driver_ahead()
     # only first value may be NaN
     assert test_data['DistanceToDriverAhead'].isnull().sum() <= 1
+    # values need to change over the course of the lap
+    assert len(test_data['DistanceToDriverAhead'].unique()) > 2
+    # DriverAhead must not be empty
+    assert (test_data['DriverAhead'].unique() != ['']).any()
 
 
 @pytest.mark.f1telapi