Merge pull request #1949 from janezd/catch-fit-errors

[FIX] Catch errors during learning in learner widgets
(cherry picked from commit af3cb70)

Author: astaric

Orange/base.py

@@ -89,7 +89,7 @@ class Model:
     def __init__(self, domain=None):
         if isinstance(self, Learner):
             domain = None
-        elif not domain:
+        elif domain is None:
             raise ValueError("unspecified domain")
         self.domain = domain
 

Orange/widgets/classify/owlogisticregression.py

@@ -77,7 +77,7 @@ def create_learner(self):
     def update_model(self):
         super().update_model()
         coef_table = None
-        if self.valid_data:
+        if self.model is not None:
             coef_table = create_coef_table(self.model)
         self.send("Coefficients", coef_table)
 

Orange/widgets/classify/owsvmclassification.py

@@ -112,9 +112,8 @@ def _report_kernel_parameters(self, items):
 
     def update_model(self):
         super().update_model()
-
         sv = None
-        if self.valid_data:
+        if self.model is not None:
             sv = self.data[self.model.skl_model.support_]
         self.send("Support vectors", sv)
 

Orange/widgets/regression/owlinearregression.py

@@ -124,7 +124,7 @@ def create_learner(self):
     def update_model(self):
         super().update_model()
         coef_table = None
-        if self.valid_data:
+        if self.model is not None:
             domain = Domain(
                     [ContinuousVariable("coef", number_of_decimals=7)],
                     metas=[StringVariable("name")])

Orange/widgets/utils/owlearnerwidget.py

@@ -110,6 +110,7 @@ class OWBaseLearner(OWWidget, metaclass=OWBaseLearnerMeta):
 
     class Error(OWWidget.Error):
         data_error = Msg("{}")
+        fitting_failed = Msg("Fitting failed.\n{}")
 
     class Warning(OWWidget.Warning):
         outdated_learner = Msg("Press Apply to submit changes.")
@@ -171,14 +172,22 @@ def update_learner(self):
         self.outdated_settings = False
         self.Warning.outdated_learner.clear()
 
+    def show_fitting_failed(self, exc):
+        """Show error when fitting fails.
+            Derived widgets can override this to show more specific messages."""
+        self.Error.fitting_failed(str(exc), shown=exc is not None)
+
     def update_model(self):
+        self.show_fitting_failed(None)
+        self.model = None
         if self.check_data():
-            self.model = self.learner(self.data)
-            self.model.name = self.learner_name
-            self.model.instances = self.data
-            self.valid_data = True
-        else:
-            self.model = None
+            try:
+                self.model = self.learner(self.data)
+            except BaseException as exc:
+                self.show_fitting_failed(exc)
+            else:
+                self.model.name = self.learner_name
+                self.model.instances = self.data
         self.send(self.OUTPUT_MODEL_NAME, self.model)
 
     def check_data(self):

Orange/widgets/utils/tests/test_owlearnerwidget.py

@@ -0,0 +1,36 @@
+# pylint: disable=missing-docstring
+from Orange.base import Learner, Model
+from Orange.data import Table, Domain
+from Orange.widgets.utils.owlearnerwidget import OWBaseLearner
+from Orange.widgets.tests.base import WidgetTest
+
+
+class TestOWBaseLearner(WidgetTest):
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.iris = Table("iris")
+
+    def test_error_on_learning(self):
+        """Check that widget shows error message when learner fails"""
+
+        class FailingLearner(Learner):
+            """A learner that fails when given data"""
+            __returns__ = Model
+
+            def __call__(self, data, *_):
+                if data is not None:
+                    raise ValueError("boom")
+                return Model(Domain([]))
+
+        class OWFailingLearner(OWBaseLearner):
+            """Widget for the above learner"""
+            name = learner_name = "foo"
+            LEARNER = FailingLearner
+            auto_apply = True
+
+        self.widget = self.create_widget(OWFailingLearner)
+        self.send_signal("Data", self.iris)
+        self.assertTrue(self.widget.Error.fitting_failed.is_shown())
+        self.send_signal("Data", None)
+        self.assertFalse(self.widget.Error.fitting_failed.is_shown())