style

firedrake/bcs.py

@@ -635,7 +635,7 @@ def reconstruct(self, field=None, V=None, subu=None, u=None, row_field=None, col
             rank = len(self.f.arguments())
             splitter = ExtractSubBlock()
             form = splitter.split(self.f, argument_indices=(row_field, col_field)[:rank])
-            if form == 0:
+            if isinstance(form, ufl.ZeroBaseForm) or form.empty():
                 # form is empty, do nothing
                 return
             if u is not None:

firedrake/formmanipulation.py

@@ -73,8 +73,8 @@ def split(self, form, argument_indices):
             assert (len(idx) == 1 for idx in self.blocks.values())
             assert (idx[0] == 0 for idx in self.blocks.values())
             return form
-        f = map_integrand_dags(self, form)
         # TODO find a way to distinguish empty Forms avoiding expand_derivatives
+        f = map_integrand_dags(self, form)
         if expand_derivatives(f).empty():
             # Get ZeroBaseForm with the right shape
             f = ZeroBaseForm(tuple(Argument(subspace(arg.function_space(),

tests/firedrake/equation_bcs/test_equation_bcs.py

@@ -190,7 +190,6 @@ def linear_poisson_mixed(solver_parameters, mesh_num, porder):
 
     solve(a == L, w, bcs=[bc2, bc3, bc4], solver_parameters=solver_parameters)
 
-
     f = cos(2 * pi * x + pi / 3) * cos(2 * pi * y)
     g = as_vector([-2 * pi * sin(2 * pi * x + pi / 3) * cos(2 * pi * y), -2 * pi * cos(2 * pi * x + pi / 3) * sin(2 * pi * y)])