Fix legacy Mahalanobis metric parameters on load

src/spikeinterface/core/tests/test_waveforms_extractor_backwards_compatibility.py

@@ -238,6 +238,9 @@ def test_load_legacy_we_with_deprecated_metrics(create_cache_folder, tmp_path):
     # qm_params should have been renamed to metric_params
     assert "qm_params" not in qm.params
     assert "metric_params" in qm.params
+    assert qm.params["metric_params"]["mahalanobis"] == {}
+    assert "isolation_distance" not in qm.params["metric_params"]
+    assert "l_ratio" not in qm.params["metric_params"]
 
     # template_metrics: deprecated names should be migrated
     tm = sorting_analyzer.get_extension("template_metrics")
@@ -249,6 +252,17 @@ def test_load_legacy_we_with_deprecated_metrics(create_cache_folder, tmp_path):
     assert "metrics_kwargs" not in tm.params
     assert "metric_params" in tm.params
 
+    # Conflicting legacy parameters must not prevent loading the analyzer.
+    params_path = we_folder / "quality_metrics" / "params.json"
+    with open(params_path) as f:
+        legacy_params = json.load(f)
+    legacy_params["qm_params"]["l_ratio"] = {"legacy_parameter": 1}
+    with open(params_path, "w") as f:
+        json.dump(legacy_params, f)
+    with pytest.warns(UserWarning, match="Using isolation_distance parameters for mahalanobis"):
+        reloaded = load_waveforms_backwards(we_folder, sorting=sorting, output="SortingAnalyzer")
+    assert reloaded.get_extension("quality_metrics").params["metric_params"]["mahalanobis"] == {}
+
 
 # @pytest.mark.skip("This test is run locally")
 # def test_read_old_waveforms_extractor_zarr():

src/spikeinterface/metrics/quality/quality_metrics.py

@@ -61,7 +61,20 @@ def _handle_backward_compatibility_on_load(self):
             self.params["metric_params"] = qm_params
             del self.params["qm_params"]
 
-        # handle metric names change: isolation_distance/l_ratio merged into mahalanobis
+        # handle metric names and parameters change: isolation_distance/l_ratio merged into mahalanobis
+        legacy_mahalanobis_params = []
+        for legacy_name in ("isolation_distance", "l_ratio"):
+            if legacy_name in self.params["metric_params"]:
+                legacy_mahalanobis_params.append(self.params["metric_params"].pop(legacy_name))
+        if legacy_mahalanobis_params and "mahalanobis" not in self.params["metric_params"]:
+            if any(params != legacy_mahalanobis_params[0] for params in legacy_mahalanobis_params[1:]):
+                warnings.warn(
+                    "Legacy isolation_distance and l_ratio parameters do not match. "
+                    "Using isolation_distance parameters for mahalanobis and discarding l_ratio parameters.",
+                    stacklevel=2,
+                )
+            self.params["metric_params"]["mahalanobis"] = legacy_mahalanobis_params[0]
+
         if "isolation_distance" in self.params["metric_names"]:
             self.params["metric_names"].remove("isolation_distance")
             if "mahalanobis" not in self.params["metric_names"]: