From 972be5225bad00aa59c06ecd0ac9cb593bc04c92 Mon Sep 17 00:00:00 2001
From: Wouter Deconinck <wdconinc@gmail.com>
Date: Fri, 22 Dec 2023 10:34:09 -0600
Subject: [PATCH] fix: forward compatibility with Acts-v31 (#1188)

### Briefly, what does this PR introduce?
~~Thanks to C++20 we can now do templated lambdas which don't require
syntactic validity of all code paths. That makes forward/backward
compatibility across Acts versions easier with constexpr lambdas.~~

Ifdefs on defined Acts major versions allow us to bypass code blocks
that are not compilable or parsable under different versions of Acts.

Ref: https://github.com/acts-project/acts/pull/2649

### What kind of change does this PR introduce?
- [ ] Bug fix (issue #__)
- [x] New feature (issue: Acts v31 compatibility)
- [ ] Documentation update
- [ ] Other: __

### Please check if this PR fulfills the following:
- [ ] Tests for the changes have been added
- [ ] Documentation has been added / updated
- [ ] Changes have been communicated to collaborators

### Does this PR introduce breaking changes? What changes might users
need to make to their code?
No.

### Does this PR change default behavior?
No.

---------

Co-authored-by: Dmitry Kalinkin <dmitry.kalinkin@gmail.com>
---
 cmake/jana_plugin.cmake                          | 6 ++++++
 src/algorithms/tracking/IterativeVertexFinder.cc | 8 ++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/cmake/jana_plugin.cmake b/cmake/jana_plugin.cmake
index c9fcf98b4a..5e0baa0a34 100644
--- a/cmake/jana_plugin.cmake
+++ b/cmake/jana_plugin.cmake
@@ -248,6 +248,12 @@ macro(plugin_add_acts _name)
         ActsPluginDD4hep
         ${ActsCore_PATH}/${CMAKE_SHARED_LIBRARY_PREFIX}ActsExamplesFramework${CMAKE_SHARED_LIBRARY_SUFFIX}
     )
+    if(${_name}_WITH_LIBRARY)
+        target_compile_definitions(${PLUGIN_NAME}_library PRIVATE "Acts_VERSION_MAJOR=${Acts_VERSION_MAJOR}")
+    endif()
+    if(${_name}_WITH_PLUGIN)
+        target_compile_definitions(${PLUGIN_NAME}_plugin PRIVATE "Acts_VERSION_MAJOR=${Acts_VERSION_MAJOR}")
+    endif()
 
 endmacro()
 
diff --git a/src/algorithms/tracking/IterativeVertexFinder.cc b/src/algorithms/tracking/IterativeVertexFinder.cc
index ff1c89625b..8ec8876642 100644
--- a/src/algorithms/tracking/IterativeVertexFinder.cc
+++ b/src/algorithms/tracking/IterativeVertexFinder.cc
@@ -86,11 +86,15 @@ std::unique_ptr<edm4eic::VertexCollection> eicrecon::IterativeVertexFinder::prod
   VertexSeeder::Config seederCfg(ipEst);
   VertexSeeder seeder(seederCfg);
   // Set up the actual vertex finder
-  VertexFinder::Config finderCfg(vertexFitter, std::move(linearizer),
-                                 std::move(seeder), ipEst);
+  VertexFinder::Config finderCfg(std::move(vertexFitter), std::move(linearizer),
+                                 std::move(seeder), std::move(ipEst));
   finderCfg.maxVertices                 = m_cfg.m_maxVertices;
   finderCfg.reassignTracksAfterFirstFit = m_cfg.m_reassignTracksAfterFirstFit;
+  #if Acts_VERSION_MAJOR >= 31
+  VertexFinder finder(std::move(finderCfg));
+  #else
   VertexFinder finder(finderCfg);
+  #endif
   VertexFinder::State state(*m_BField, m_fieldctx);
   VertexFinderOptions finderOpts(m_geoctx, m_fieldctx);