Fix bug in required-variables (#306)

* Fix Enum bug

* Required-variable doesn't recognise input variables
Fixes #305

* Versioning

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixed:
+    - Bug in labour supply responses.

policyengine_core/simulations/simulation.py

@@ -635,15 +635,20 @@ def _calculate(
                     return value
 
         if variable.requires_computation_after is not None:
-            if variable.requires_computation_after not in [
+            variables_in_stack = [
                 node.get("name") for node in self.tracer.stack
-            ]:
+            ]
+            variable_in_stack = (
+                variable.requires_computation_after in variables_in_stack
+            )
+            required_is_known_periods = self.get_holder(
+                variable.requires_computation_after
+            ).get_known_periods()
+            if (not variable_in_stack) and (
+                not len(required_is_known_periods) > 0
+            ):
                 raise ValueError(
-                    f"Variable {variable_name} requires {variable.requires_computation_after} to be requested first. The full stack is: "
-                    + "\n".join(
-                        f"  - {node.get('name')} {node.get('period')}, {node.get('branch_name')}"
-                        for node in self.tracer.stack
-                    )
+                    f"Variable {variable_name} requires {variable.requires_computation_after} to be requested first. That variable is known in: {required_is_known_periods}. The full stack is: {variables_in_stack}. {variable_in_stack, len(required_is_known_periods) > 0}"
                 )
         alternate_period_handling = False
         if variable.definition_period == MONTH and period.unit == YEAR: