scikit-learn · glemaitre · Sep 6, 2021 · Aug 26, 2021 · Sep 4, 2021 · Sep 4, 2021
diff --git a/doc/whats_new/v1.0.rst b/doc/whats_new/v1.0.rst
@@ -792,6 +792,13 @@ Changelog
   `n_features_in_` and will be removed in 1.2. :pr:`20240` by
   :user:`Jérémie du Boisberranger <jeremiedbb>`.
 
+:mod:`sklearn.svm`
+...................
+
+- |API| The parameter `**params` of :func:`svm.OneClassSVM.fit` is
+  deprecated and will be removed in 1.2.
+  :pr:`20843` by :user:`Juan Martín Loyola <jmloyola>`.
+
 :mod:`sklearn.tree`
 ...................
 

diff --git a/sklearn/svm/_classes.py b/sklearn/svm/_classes.py
@@ -1,4 +1,5 @@
 import numpy as np
+import warnings
 
 from ._base import _fit_liblinear, BaseSVC, BaseLibSVM
 from ..base import BaseEstimator, RegressorMixin, OutlierMixin
@@ -1604,6 +1605,11 @@ def fit(self, X, y=None, sample_weight=None, **params):
         **params : dict
             Additional fit parameters.
 
+            .. deprecated:: 1.0
+                The `fit` method will not longer accept extra keyword
+                parameters in 1.2. These keyword parameters were
+                already discarded.
+
         Returns
         -------
         self : object
@@ -1613,7 +1619,16 @@ def fit(self, X, y=None, sample_weight=None, **params):
         -----
         If X is not a C-ordered contiguous array it is copied.
         """
-        super().fit(X, np.ones(_num_samples(X)), sample_weight=sample_weight, **params)
+        # TODO: Remove in v1.2
+        if len(params) > 0:
+            warnings.warn(
+                "Passing additional keyword parameters has no effect and is "
+                "deprecated in 1.0. An error will be raised from 1.2 and "
+                "beyond. The ignored keyword parameter(s) are: "
+                f"{params.keys()}.",
+                FutureWarning,
+            )
+        super().fit(X, np.ones(_num_samples(X)), sample_weight=sample_weight)
         self.offset_ = -self._intercept_
         return self
 

diff --git a/sklearn/svm/tests/test_svm.py b/sklearn/svm/tests/test_svm.py
@@ -6,6 +6,7 @@
 import numpy as np
 import itertools
 import pytest
+import re
 
 from numpy.testing import assert_array_equal, assert_array_almost_equal
 from numpy.testing import assert_almost_equal
@@ -299,6 +300,22 @@ def test_oneclass_score_samples():
     )
 
 
+# TODO: Remove in v1.2
+def test_oneclass_fit_params_is_deprecated():
+    clf = svm.OneClassSVM()
+    params = {
+        "unused_param": "",
+        "extra_param": None,
+    }
+    msg = (
+        "Passing additional keyword parameters has no effect and is deprecated "
+        "in 1.0. An error will be raised from 1.2 and beyond. The ignored "
+        f"keyword parameter(s) are: {params.keys()}."
+    )
+    with pytest.warns(FutureWarning, match=re.escape(msg)):
+        clf.fit(X, **params)
+
+
 def test_tweak_params():
     # Make sure some tweaking of parameters works.
     # We change clf.dual_coef_ at run time and expect .predict() to change