From 1148219311dbf4d8ef35d76467b82c03c6b52d6e Mon Sep 17 00:00:00 2001
From: tmadlener <thomas.madlener@desy.de>
Date: Thu, 11 Jan 2024 10:36:19 +0100
Subject: [PATCH 1/4] Add a small downstream project for testing

---
 .../CMakeLists.txt                            | 15 +++++++++++++
 .../lcio_test_program.cpp                     | 22 +++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 tests/downstream-project-cmake-test/CMakeLists.txt
 create mode 100644 tests/downstream-project-cmake-test/lcio_test_program.cpp

diff --git a/tests/downstream-project-cmake-test/CMakeLists.txt b/tests/downstream-project-cmake-test/CMakeLists.txt
new file mode 100644
index 000000000..77f70f5c2
--- /dev/null
+++ b/tests/downstream-project-cmake-test/CMakeLists.txt
@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.14)
+
+project(DownstreamProjectUsingLCIO)
+
+find_package(LCIO REQUIRED)
+
+# Make sure that the LCIO version is set and usableas a version
+if (${LCIO_VERSION} VERSION_GREATER "0.0.0")
+  message(STATUS "Found LCIO version " ${LCIO_VERSION})
+else()
+  message(FATAL_ERROR "Cannot determine LCIO_VERSION")
+endif()
+
+add_executable(lcio_test_program lcio_test_program.cpp)
+target_link_libraries(lcio_test_program PRIVATE LCIO::lcio)
diff --git a/tests/downstream-project-cmake-test/lcio_test_program.cpp b/tests/downstream-project-cmake-test/lcio_test_program.cpp
new file mode 100644
index 000000000..a53be69fa
--- /dev/null
+++ b/tests/downstream-project-cmake-test/lcio_test_program.cpp
@@ -0,0 +1,22 @@
+#include "EVENT/LCEvent.h"
+#include "IMPL/LCCollectionVec.h"
+#include "IMPL/LCEventImpl.h"
+#include "IMPL/MCParticleImpl.h"
+#include "MT/LCWriter.h"
+
+int main() {
+  auto mcp = new IMPL::MCParticleImpl();
+  mcp->setPDG(11);
+
+  auto coll = new IMPL::LCCollectionVec(EVENT::LCIO::MCPARTICLE);
+  coll->addElement(mcp);
+
+  auto event = new IMPL::LCEventImpl();
+  event->addCollection(coll, "mcps");
+
+  auto writer = MT::LCWriter();
+  writer.open("test.slcio");
+  writer.writeEvent(event);
+
+  return 0;
+}

From c514a653be1d3ec8593702564f2cffe708e977c8 Mon Sep 17 00:00:00 2001
From: tmadlener <thomas.madlener@desy.de>
Date: Thu, 11 Jan 2024 10:39:33 +0100
Subject: [PATCH 2/4] Build downstream project in CI

---
 .github/workflows/key4hep.yml | 7 +++++++
 .github/workflows/linux.yml   | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/.github/workflows/key4hep.yml b/.github/workflows/key4hep.yml
index 9db920284..1b74f57da 100644
--- a/.github/workflows/key4hep.yml
+++ b/.github/workflows/key4hep.yml
@@ -28,3 +28,10 @@ jobs:
           make -k
           make install
           ctest --output-on-failure
+          echo "::group::Test downstream build"
+          cd -
+          export CMAKE_PREFIX_PATH=$PWD/install:$CMAKE_PREFIX_PATH
+          cd tests/downstream-project-cmake-test
+          mkdir build && cd build
+          cmake .. -DCMAKE_CXX_STANDARD=17
+          make -k
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index f93a904a3..084e222cb 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -30,3 +30,10 @@ jobs:
           make -k
           make install
           ctest --output-on-failure
+          echo "::group::Test downstream build"
+          cd -
+          export CMAKE_PREFIX_PATH=$PWD/install:$CMAKE_PREFIX_PATH
+          cd tests/downstream-project-cmake-test
+          mkdir build && cd build
+          cmake .. -DCMAKE_CXX_STANDARD=17
+          make -k

From e1c31d1b34c2ed06ed30b62957a8fdbbf481699f Mon Sep 17 00:00:00 2001
From: tmadlener <thomas.madlener@desy.de>
Date: Thu, 11 Jan 2024 10:51:49 +0100
Subject: [PATCH 3/4] Update CMake config template to work with new sio
 packaging

---
 cmake/LCIOConfig.cmake.in | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/cmake/LCIOConfig.cmake.in b/cmake/LCIOConfig.cmake.in
index e1b545636..ef304a1d6 100644
--- a/cmake/LCIOConfig.cmake.in
+++ b/cmake/LCIOConfig.cmake.in
@@ -68,12 +68,7 @@ CHECK_PACKAGE_LIBS( LCIO lcio @CHECK_PACKAGE_SIO_LIBRARY@ )
 
 
 include(CMakeFindDependencyMacro)
-if("@CHECK_PACKAGE_SIO_LIBRARY@" STREQUAL "") 
-  find_dependency(SIO REQUIRED)
-else()
-  find_dependency(ZLIB REQUIRED)
-  include("${CMAKE_CURRENT_LIST_DIR}/SIOTargets.cmake")
-endif()
+find_dependency(SIO @SIO_VERSION@)
 
 # Include the targets file to create the imported targets that a client can link
 # to or execute

From 05d0e0ed5229c9c057400586c9065207b909ba9b Mon Sep 17 00:00:00 2001
From: tmadlener <thomas.madlener@desy.de>
Date: Thu, 11 Jan 2024 11:35:55 +0100
Subject: [PATCH 4/4] Bump minimum required SIO version to v00-01

---
 CMakeLists.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4f2a3231e..d44a9424d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -161,8 +161,8 @@ eval $*
 
 ENDIF()
 
-# Deal with SIO
-FIND_PACKAGE( SIO QUIET )
+# Deal with SIO (we need at least 0.1 since there are no targets before)
+FIND_PACKAGE( SIO 0.1 QUIET )
 
 IF( NOT SIO_FOUND )
   MESSAGE( STATUS "SIO not found on your system. Using builtin sio" )