Make cofunctionals terminal, and test

test/test_equals.py

@@ -1,6 +1,7 @@
 """Test of expression comparison."""
 
 from ufl import Coefficient, Cofunction, FunctionSpace, Mesh, triangle
+from ufl.exprcontainers import ExprList
 from ufl.finiteelement import FiniteElement
 from ufl.pullback import identity_pullback
 from ufl.sobolevspace import H1
@@ -69,6 +70,10 @@ def test_comparison_of_cofunctions():
     assert not v1 == u1
     assert not v2 == u2
 
+    # Objects in ExprList as happens when taking derivatives.
+    assert ExprList(v1, v1) == ExprList(v1, v1b)
+    assert not ExprList(v1, v2) == ExprList(v1, v1)
+
 
 def test_comparison_of_products():
     V = FiniteElement("Lagrange", triangle, 1, (), identity_pullback, H1)

ufl/coefficient.py

@@ -118,6 +118,7 @@ class Cofunction(BaseCoefficient, BaseForm):
     )
     _primal = False
     _dual = True
+    _ufl_is_terminal_ = True
 
     __eq__ = BaseForm.__eq__
 

ufl/formatting/ufl2unicode.py

@@ -485,10 +485,26 @@ def coefficient(self, o):
             return f"{var}{subscript_number(i)}"
         return self.coefficient_names[o.count()]
 
+    def cofunction(self, o):
+        """Format a cofunction."""
+        if self.coefficient_names is None:
+            i = o.count()
+            var = "cofunction"
+            if len(o.ufl_shape) == 1:
+                var += UC.combining_right_arrow_above
+            elif len(o.ufl_shape) > 1 and self.colorama_bold:
+                var = f"{colorama.Style.BRIGHT}{var}{colorama.Style.RESET_ALL}"
+            return f"{var}{subscript_number(i)}"
+        return self.coefficient_names[o.count()]
+
     def base_form_operator(self, o):
         """Format a base_form_operator."""
         return "BaseFormOperator"
 
+    def action(self, o, a, b):
+        """Format an Action."""
+        return f"Action({a}, {b})"
+
     def constant(self, o):
         """Format a constant."""
         i = o.count()