check for input length in Monatomic.n_closest

kwant/lattice.py

@@ -484,6 +484,9 @@ class Monatomic(builder.SiteFamily, Polyatomic):
         sites : numpy array
             An array with sites coordinates.
         """
+        if len(pos) != len(self.offset):
+            raise ValueError("Incorrect dimensionality of 'pos'.")
+
         # TODO (Anton): transform to tinyarrays, once ta indexing is better.
         return np.dot(lll.cvp(pos - self.offset, self.reduced_vecs,
                               n=n, group_by_length=group_by_length, rtol=rtol),

kwant/tests/test_lattice.py

@@ -27,6 +27,9 @@ def test_closest():
         tag = rng.randint(10, size=(3,))
         assert lat.closest(lat(*tag).pos) == tag
 
+    # Closest should raise if input has a wrong dimensionality
+    raises(ValueError, lattice.square().closest, [0])
+
 
 def test_general():
     for lat in (lattice.general(((1, 0), (0.5, 0.5))),