Table.add_column - Do not try to insert in locked empty array

Author: PrimozGodec

Orange/data/table.py

@@ -1452,8 +1452,10 @@ def add_column(self, variable, data, to_metas=None):
             attrs += (variable, )
         domain = Domain(attrs, classes, metavars)
         new_table = self.transform(domain)
-        with new_table.unlocked(new_table.metas if to_metas else new_table.X):
-            new_table.set_column(variable, data)
+        if len(new_table) > 0:
+            # empty array doesn't unlock - insert only if array not empty
+            with new_table.unlocked(new_table.metas if to_metas else new_table.X):
+                new_table.set_column(variable, data)
         return new_table
 
     def is_sparse(self):

Orange/data/tests/test_table.py

@@ -263,6 +263,22 @@ def test_with_column(self):
             tabw.metas,
             np.hstack((tab.metas, np.array(list("abcde")).reshape(5, -1))))
 
+    def test_add_column_empty(self):
+        a, b = ContinuousVariable("a"), ContinuousVariable("b")
+        table = Table.from_list(Domain([a]), [])
+
+        new_table = table.add_column(b, [], to_metas=True)
+        self.assertTupleEqual(new_table.domain.attributes, (a,))
+        self.assertTupleEqual(new_table.domain.metas, (b,))
+        self.assertTupleEqual((0, 1), new_table.X.shape)
+        self.assertTupleEqual((0, 1), new_table.metas.shape)
+
+        new_table = table.add_column(ContinuousVariable("b"), [], to_metas=False)
+        self.assertTupleEqual(new_table.domain.attributes, (a, b))
+        self.assertTupleEqual(new_table.domain.metas, ())
+        self.assertTupleEqual((0, 2), new_table.X.shape)
+        self.assertTupleEqual((0, 0), new_table.metas.shape)
+
     def test_copy(self):
         domain = Domain([ContinuousVariable("x")],
                         ContinuousVariable("y"),