From 5a1c3abdba5d5e1d5772d89b782c827c0776a01a Mon Sep 17 00:00:00 2001
From: Thibault Cordier <124613154+thibaultcordier@users.noreply.github.com>
Date: Thu, 21 Dec 2023 16:26:39 +0100
Subject: [PATCH] UPD: add DeprecationWarning for partial_fit

Co-authored-by: Vincent Blot <52573624+vincentblot28@users.noreply.github.com>
---
 mapie/regression/time_series_regression.py |  7 +++++++
 mapie/tests/test_time_series_regression.py | 10 ++++++++++
 2 files changed, 17 insertions(+)

diff --git a/mapie/regression/time_series_regression.py b/mapie/regression/time_series_regression.py
index bb52a50a8..2237b7da5 100644
--- a/mapie/regression/time_series_regression.py
+++ b/mapie/regression/time_series_regression.py
@@ -158,6 +158,13 @@ def partial_fit(
             If the length of ``y`` is greater than
             the length of the training set.
         """
+        warnings.warn(
+                "WARNING: Deprecated method. "
+                + "The method \"partial_fit\" is outdated. "
+                + "Prefer to use \"update\" instead to keep "
+                + "the same behavior in the future.",
+                DeprecationWarning
+            )
         check_is_fitted(self, self.fit_attributes)
         X, y = cast(NDArray, X), cast(NDArray, y)
         m, n = len(X), len(self.conformity_scores_)
diff --git a/mapie/tests/test_time_series_regression.py b/mapie/tests/test_time_series_regression.py
index f7ce95917..1bae85c22 100644
--- a/mapie/tests/test_time_series_regression.py
+++ b/mapie/tests/test_time_series_regression.py
@@ -498,6 +498,16 @@ def test_aci__get_alpha_with_unknown_alpha() -> None:
     np.testing.assert_allclose(mapie_ts_reg.current_alpha[0.2], 0.3, rtol=1e-3)
 
 
+def test_deprecated_partial_fit_warning(method: str) -> None:
+    """Test that a warning is raised if use partial_fit"""
+    mapie_ts_reg = MapieTimeSeriesRegressor(method='enbpi', cv=-1)
+    mapie_ts_reg.fit(X_toy, y_toy)
+    with pytest.warns(
+        DeprecationWarning, match=r".*WARNING: Deprecated method.*"
+    ):
+        mapie_ts_reg = mapie_ts_reg.partial_fit(X_toy, y_toy)
+
+
 @pytest.mark.parametrize("method", ["wrong_method"])
 def test_method_error_in_update(monkeypatch: Any, method: str) -> None:
     """Test else condition for the method in .update"""