feat(edm): Add functions to create and return track(state) proxies

Core/include/Acts/EventData/MultiTrajectory.hpp

@@ -1141,6 +1141,17 @@ class MultiTrajectory {
     return {*this, istate};
   }
 
+  /// Add a track state to the container and return a track state proxy to it
+  /// This effectively calls @c addTrackState and @c getTrackState
+  /// @note Only available if the track state container is not read-only
+  /// @return a track state proxy to the newly added track state
+  template <bool RO = ReadOnly, typename = std::enable_if_t<!RO>>
+  TrackStateProxy makeTrackState(
+      TrackStatePropMask mask = TrackStatePropMask::All,
+      IndexType iprevious = kInvalid) {
+    return getTrackState(addTrackState(mask, iprevious));
+  }
+
   /// Visit all previous states starting at a given endpoint.
   ///
   /// @param iendpoint  index of the last state

Core/include/Acts/EventData/TrackContainer.hpp

@@ -127,6 +127,15 @@ class TrackContainer {
     return track.index();
   }
 
+  /// Add a track to the container and return a track proxy to it
+  /// This effectively calls @c addTrack and @c getTrack
+  /// @note Only available if the track container is not read-only
+  /// @return a track proxy to the newly added track
+  template <bool RO = ReadOnly, typename = std::enable_if_t<!RO>>
+  TrackProxy makeTrack() {
+    return getTrack(addTrack());
+  }
+
   /// Remove a track at index @p itrack from the container
   /// @note This invalidates all track proxies!
   /// @param itrack The index of the track to remove

Core/include/Acts/EventData/detail/MultiTrajectoryTestsCommon.hpp

@@ -110,6 +110,16 @@ class MultiTrajectoryTestsCommon {
     }
     BOOST_CHECK_EQUAL_COLLECTIONS(predictedsAct.begin(), predictedsAct.end(),
                                   predicteds.begin(), predicteds.end());
+
+    {
+      trajectory_t t2 = m_factory.create();
+      auto ts = t2.makeTrackState(kMask);
+      BOOST_CHECK_EQUAL(t2.size(), 1);
+      auto ts2 = t2.makeTrackState(kMask, ts.index());
+      BOOST_CHECK_EQUAL(t2.size(), 2);
+      BOOST_CHECK_EQUAL(ts.previous(), MultiTrajectoryTraits::kInvalid);
+      BOOST_CHECK_EQUAL(ts2.previous(), ts.index());
+    }
   }
 
   void testClear() {

Tests/UnitTests/Core/EventData/TrackTests.cpp

@@ -206,6 +206,21 @@ BOOST_AUTO_TEST_CASE(BuildSharedPtr) {
   BOOST_CHECK_EQUAL(vtc.get(), &copy.container());
 }
 
+BOOST_AUTO_TEST_CASE(BuildConvenience) {
+  VectorMultiTrajectory mtj{};
+  VectorTrackContainer vtc{};
+  TrackContainer tc{vtc, mtj};
+
+  BOOST_CHECK_EQUAL(tc.size(), 0);
+  auto track1 = tc.makeTrack();
+  BOOST_CHECK_EQUAL(tc.size(), 1);
+  auto track2 = tc.makeTrack();
+  BOOST_CHECK_EQUAL(tc.size(), 2);
+
+  BOOST_CHECK_EQUAL(track1.index(), 0);
+  BOOST_CHECK_EQUAL(track2.index(), 1);
+}
+
 BOOST_AUTO_TEST_CASE_TEMPLATE(Build, factory_t, holder_types) {
   factory_t factory;