Snapshot mutable property values when saving filter history

filterpy/common/helpers.py

@@ -127,7 +127,7 @@ def save(self):
         # if the class uses properties that compute data only when
         # accessed
         for prop in self.properties:
-            self._DL[prop[0]].append(getattr(kf, prop[0]))
+            self._DL[prop[0]].append(copy.deepcopy(getattr(kf, prop[0])))
 
         v = copy.deepcopy(kf.__dict__)
 

filterpy/common/tests/test_saver_property_snapshots.py

@@ -0,0 +1,41 @@
+import numpy as np
+from filterpy.common import Saver
+
+
+class FilterWithProperties:
+    def __init__(self):
+        self._state = np.array([1.0, 2.0])
+        self._metadata = {"history": [1]}
+
+    @property
+    def state(self):
+        return self._state
+
+    @property
+    def metadata(self):
+        return self._metadata
+
+
+def test_property_snapshots_do_not_change_with_live_filter():
+    model = FilterWithProperties()
+    saver = Saver(model, save_current=True)
+    model._state[:] = [3.0, 4.0]
+    model._metadata["history"].append(2)
+    saver.save()
+    model._state[:] = [5.0, 6.0]
+    model._metadata["history"].append(3)
+    np.testing.assert_array_equal(saver.state, [[1.0, 2.0], [3.0, 4.0]])
+    assert saver.metadata == [{"history": [1]}, {"history": [1, 2]}]
+    saver.state[0][0] = 99
+    np.testing.assert_array_equal(model.state, [5.0, 6.0])
+    np.testing.assert_array_equal(saver.state[1], [3.0, 4.0])
+
+
+def test_ignored_property_is_never_read():
+    class Model:
+        @property
+        def ignored(self):
+            raise AssertionError("ignored property accessed")
+
+    saver = Saver(Model(), ignore=("ignored",), save_current=True)
+    assert len(saver) == 1