Fix #431

CHANGES.rst

@@ -1,3 +1,9 @@
+v3.0.2
+======
+    * Properly raise warning if a custom pickling handler returns None. (#433)
+    * Fix issue with serialization of certain sklearn objects breaking when
+      the numpy handler was enabled. (#431) (+434)
+
 v3.0.1
 ======
     * Remove accidental pin of setuptools to versions below 59. This allows

jsonpickle/ext/numpy.py

@@ -324,6 +324,9 @@ def restore(self, data):
         else:
             # decode array view, which references the data of another array
             base = self.context.restore(base, reset=False)
+            if not isinstance(base, np.ndarray):
+                # the object is probably a nested list
+                base = np.array(base)
             assert (
                 base.flags.forc
             ), "Current implementation assumes base is C or F contiguous"

tests/sklearn_test.py

@@ -4,6 +4,8 @@
 
 try:
     import numpy as np
+    import sklearn.datasets
+    from sklearn.linear_model import LogisticRegression
     from sklearn.tree import DecisionTreeClassifier
 except ImportError:
     pytest.skip('sklearn is not available', allow_module_level=True)
@@ -53,5 +55,22 @@ def test_decision_tree():
         assert actual.get_depth() == classifier.get_depth()
 
 
+def test_nested_array_serialization():
+    iris = sklearn.datasets.load_iris()
+    X = iris.data[:, :2]
+    y = (iris.target != 0) * 1
+
+    pipe = LogisticRegression(solver="lbfgs")
+    pipe.fit(X, y)
+    res = pipe.predict(X)
+
+    # Try serializing/deserializing.
+    # Pipe is a LogisticRegression object that contains a nested array
+    js = jsonpickle.dumps(pipe)
+    pipe2 = jsonpickle.loads(js)
+    # coef_ only appears on an instance that has already been fit to something
+    assert np.all(pipe.coef_ == pipe2.coef_)
+
+
 if __name__ == '__main__':
     pytest.main([__file__])