Throw an error when concatenations have different number of children

src/pybamm/expression_tree/binary_operators.py

@@ -856,12 +856,17 @@ def _simplified_binary_broadcast_concatenation(
         elif isinstance(right, pybamm.Concatenation) and not isinstance(
             right, pybamm.ConcatenationVariable
         ):
-            return left.create_copy(
-                [
-                    operator(left_child, right_child)
-                    for left_child, right_child in zip(left.orphans, right.orphans)
-                ]
-            )
+            if len(left.orphans) == len(right.orphans):
+                return left.create_copy(
+                    [
+                        operator(left_child, right_child)
+                        for left_child, right_child in zip(left.orphans, right.orphans)
+                    ]
+                )
+            else:
+                raise AssertionError(
+                    "Concatenations must have the same number of children"
+                )
     if isinstance(right, pybamm.Concatenation) and not isinstance(
         right, pybamm.ConcatenationVariable
     ):

src/pybamm/models/full_battery_models/base_battery_model.py

@@ -990,6 +990,16 @@ def options(self, extra_options):
                 f"must use surface formulation to solve {self!s} with hydrolysis"
             )
 
+        if isinstance(self, pybamm.lithium_ion.DFN):
+            if options["working electrode"] == "positive":
+                if (
+                    options["thermal"] == "lumped"
+                    or options["calculate heat source for isothermal models"] == "true"
+                ):
+                    raise pybamm.OptionError(
+                        "Due to a known bug, half-cell models are not currently compatible with thermal models."
+                    )
+
         self._options = options
 
     def set_standard_output_variables(self):

tests/unit/test_expression_tree/test_concatenations.py

@@ -445,3 +445,18 @@ def test_to_from_json(self, mocker):
 
         # test _from_json
         assert pybamm.NumpyConcatenation._from_json(np_json) == conc_np
+
+    def test_same_number_of_children(self):
+        a = pybamm.Variable("y", domain=["1", "2"])
+        b = pybamm.Variable("z", domain=["3"])
+
+        d1 = pybamm.Variable("d1", domain=["1"])
+        d2 = pybamm.Variable("d2", domain=["2"])
+        d3 = pybamm.Variable("d3", domain=["3"])
+
+        d_concat = pybamm.concatenation(pybamm.sin(d1), pybamm.sin(d2), pybamm.sin(d3))
+        a_concat = pybamm.concatenation(pybamm.sin(a), pybamm.sin(b))
+        with pytest.raises(
+            AssertionError, match="Concatenations must have the same number of children"
+        ):
+            a_concat + d_concat

tests/unit/test_models/test_full_battery_models/test_lithium_ion/base_lithium_ion_half_cell_tests.py

@@ -2,6 +2,8 @@
 # Base unit tests for lithium-ion half-cell models
 # This is achieved by using the {"working electrdode": "positive"} option
 #
+import pybamm
+import pytest
 
 
 class BaseUnitTestLithiumIonHalfCell:
@@ -81,8 +83,16 @@ def test_well_posed_asymmetric_ec_reaction_limited_sei(self):
 
     def test_well_posed_lumped_thermal(self):
         options = {"thermal": "lumped"}
-        self.check_well_posedness(options)
+        if self.model == pybamm.lithium_ion.DFN:
+            with pytest.raises(pybamm.OptionError):
+                self.check_well_posedness(options)
+        else:
+            self.check_well_posedness(options)
 
     def test_well_posed_lumped_thermal_hom(self):
         options = {"thermal": "lumped", "heat of mixing": "true"}
-        self.check_well_posedness(options)
+        if self.model == pybamm.lithium_ion.DFN:
+            with pytest.raises(pybamm.OptionError):
+                self.check_well_posedness(options)
+        else:
+            self.check_well_posedness(options)