Fix incorrect default seasons

soccerdata/_common.py

@@ -460,12 +460,30 @@ def seasons(self) -> list[str]:
     def seasons(self, seasons: str | int | Iterable[str | int] | None) -> None:
         if seasons is None:
             logger.info("No seasons provided. Will retrieve data for the last 5 seasons.")
-            year = datetime.now(tz=timezone.utc).year
-            seasons = [f"{y - 1}-{y}" for y in range(year, year - 6, -1)]
+            seasons = self._default_seasons(datetime.now(tz=timezone.utc))
         if isinstance(seasons, (str, int)):
             seasons = [seasons]
         self._season_ids = [self._season_code.parse(s) for s in seasons]
 
+    def _default_seasons(self, now: datetime) -> list[str]:
+        """Return the last 5 seasons, ending with the current one.
+
+        The current season is derived from the season calendar, not from the
+        calendar year. For a multi-year league (e.g. Aug-May), the current
+        season ends in the next calendar year during the second half of the
+        year, so the end year is shifted by one during that period. For a
+        single-year league, the season id equals the start year of the
+        generated range, so the end year is one ahead of the calendar year.
+        """
+        end_year = now.year
+        if (
+            self._season_code == SeasonCode.SINGLE_YEAR
+            or self._season_code == SeasonCode.MULTI_YEAR
+            and now.month >= 8
+        ):
+            end_year += 1
+        return [f"{y - 1}-{y}" for y in range(end_year, end_year - 5, -1)]
+
 
 class BaseRequestsReader(BaseReader):
     """Base class for readers that use the Python requests module."""

tests/test_common.py

@@ -268,6 +268,50 @@ def test_is_complete_undefined_league(mocker):
         reader._is_complete("FAKE-Dummy League", "1920")
 
 
+def test_default_seasons(mocker):
+    """It should default to the last 5 seasons ending with the current season."""
+    reader = BaseRequestsReader(no_store=True)
+    october = datetime(2024, 10, 30, 12, 0, tzinfo=timezone.utc)
+    march = datetime(2024, 3, 30, 12, 0, tzinfo=timezone.utc)
+
+    # multi-year leagues: the current season ends next year after August
+    mocker.patch.object(
+        BaseRequestsReader,
+        "_season_code",
+        new_callable=mocker.PropertyMock,
+        return_value=SeasonCode.MULTI_YEAR,
+    )
+    assert [SeasonCode.MULTI_YEAR.parse(s) for s in reader._default_seasons(october)] == [
+        "2425",
+        "2324",
+        "2223",
+        "2122",
+        "2021",
+    ]
+    assert [SeasonCode.MULTI_YEAR.parse(s) for s in reader._default_seasons(march)] == [
+        "2324",
+        "2223",
+        "2122",
+        "2021",
+        "1920",
+    ]
+
+    # single-year leagues: seasons are single calendar years
+    mocker.patch.object(
+        BaseRequestsReader,
+        "_season_code",
+        new_callable=mocker.PropertyMock,
+        return_value=SeasonCode.SINGLE_YEAR,
+    )
+    assert [SeasonCode.SINGLE_YEAR.parse(s) for s in reader._default_seasons(october)] == [
+        "2024",
+        "2023",
+        "2022",
+        "2021",
+        "2020",
+    ]
+
+
 # Season codes
 def test_season_pattern1a():
     assert SeasonCode.MULTI_YEAR.parse("9495") == "9495"