feat: Introduce propagator stage (#2621)

Currently it is not possible to discover in which stage of propagation we are in the actors and aborters. By introducing a propagator stage enum, adding it to the state and setting it in the proagator loop this can be used in the actors and aborters.

Pulled out of #2603

Core/include/Acts/Propagator/Propagator.hpp

@@ -32,6 +32,15 @@
 
 namespace Acts {
 
+/// @brief Different stages during propagation
+enum class PropagatorStage {
+  invalid,          ///< Invalid stage
+  prePropagation,   ///< Before the propagation
+  postPropagation,  ///< After the propagation
+  preStep,          ///< Before a step
+  postStep,         ///< After a step
+};
+
 /// @brief Simple class holding result of propagation call
 ///
 /// @tparam parameters_t Type of final track parameters
@@ -270,6 +279,9 @@ class Propagator final {
           navigation{std::move(navigationIn)},
           geoContext(topts.geoContext) {}
 
+    /// Propagation stage
+    PropagatorStage stage = PropagatorStage::invalid;
+
     /// These are the options - provided for each propagation step
     propagator_options_t options;
 

Core/include/Acts/Propagator/Propagator.ipp

@@ -20,6 +20,8 @@ auto Acts::Propagator<S, N>::propagate_impl(propagator_state_t& state,
   // Pre-stepping call to the navigator and action list
   ACTS_VERBOSE("Entering propagation.");
 
+  state.stage = PropagatorStage::prePropagation;
+
   // Navigator initialize state call
   m_navigator.initialize(state, m_stepper);
   // Pre-Stepping call to the action list
@@ -41,6 +43,7 @@ auto Acts::Propagator<S, N>::propagate_impl(propagator_state_t& state,
     // Propagation loop : stepping
     for (; result.steps < state.options.maxSteps; ++result.steps) {
       // Pre-Stepping: target setting
+      state.stage = PropagatorStage::preStep;
       m_navigator.preStep(state, m_stepper);
       // Perform a propagation step - it takes the propagation state
       Result<double> res = m_stepper.step(state, m_navigator);
@@ -57,6 +60,7 @@ auto Acts::Propagator<S, N>::propagate_impl(propagator_state_t& state,
       }
       // Post-stepping:
       // navigator post step call - action list - aborter list
+      state.stage = PropagatorStage::postStep;
       m_navigator.postStep(state, m_stepper);
       state.options.actionList(state, m_stepper, m_navigator, result, logger());
       if (state.options.abortList(state, m_stepper, m_navigator, result,
@@ -69,6 +73,8 @@ auto Acts::Propagator<S, N>::propagate_impl(propagator_state_t& state,
     ACTS_VERBOSE("Propagation terminated without going into stepping loop.");
   }
 
+  state.stage = PropagatorStage::postPropagation;
+
   // if we didn't terminate normally (via aborters) set navigation break.
   // this will trigger error output in the lines below
   if (!terminatedNormally) {