From 6dde823d4cb884638c323d5cd5d7efc33bbf16dd Mon Sep 17 00:00:00 2001
From: Robin Mueller <muellerr@irs.uni-stuttgart.de>
Date: Tue, 3 May 2022 17:17:48 +0200
Subject: [PATCH] improve dependency handling (same as fsfw)

---
 CMakeLists.txt | 43 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 11 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 77509188..2fbcf0fb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -118,7 +118,7 @@ set(SIMPLE_OBSW_NAME eive-simple)
 set(UNITTEST_NAME eive-unittest)
 set(LIB_FSFW_NAME fsfw)
 set(LIB_EIVE_MISSION eive-mission)
-set(LIB_ETL_NAME etl)
+set(LIB_ETL_TARGET etl::etl)
 set(LIB_CSP_NAME libcsp)
 set(LIB_LWGPS_NAME lwgps)
 set(LIB_ARCSEC wire)
@@ -325,13 +325,21 @@ add_subdirectory(${UNITTEST_PATH})
 
 # This should have already been downloaded by the FSFW
 # Still include it to be safe
-include(FetchContent)
-FetchContent_Declare(
-    etl
-    GIT_REPOSITORY https://github.com/ETLCPP/etl
-    GIT_TAG        ${FSFW_ETL_LIB_VERSION}
-)
-FetchContent_MakeAvailable(etl)
+find_package(etl ${FSFW_ETL_LIB_MAJOR_VERSION} CONFIG QUIET)
+# Not installed, so use FetchContent to download and provide etl
+if(NOT etl_FOUND)
+    message(STATUS
+        "No ETL installation was found with find_package. Installing and providing "
+        "etl with FindPackage"
+    )
+    include(FetchContent)
+    FetchContent_Declare(
+        etl
+        GIT_REPOSITORY https://github.com/ETLCPP/etl
+        GIT_TAG        ${FSFW_ETL_LIB_VERSION}
+    )
+    list(APPEND FSFW_FETCH_CONTENT_TARGETS etl)
+endif()
 
 # Use same Catch2 version as framework
 if (NOT(TGT_BSP MATCHES "arm/te0720-1cfa") AND NOT(TGT_BSP MATCHES "arm/q7s"))
@@ -348,8 +356,21 @@ if (NOT(TGT_BSP MATCHES "arm/te0720-1cfa") AND NOT(TGT_BSP MATCHES "arm/q7s"))
             GIT_TAG        ${FSFW_CATCH2_LIB_VERSION}
         )
 
-        FetchContent_MakeAvailable(Catch2)
-        #fixes regression -preview4, to be confirmed in later releases
+        list(APPEND FSFW_FETCH_CONTENT_TARGETS Catch2)
+    endif()
+endif()
+
+# The documentation for FetchContent recommends declaring all the dependencies
+# before making them available. We make all declared dependency available here
+# after their declaration
+if(FSFW_FETCH_CONTENT_TARGETS)
+    FetchContent_MakeAvailable(${FSFW_FETCH_CONTENT_TARGETS})
+    if(TARGET etl)
+        add_library(${LIB_ETL_TARGET} ALIAS etl)
+    endif()
+    if(TARGET Catch2)
+        # Fixes regression -preview4, to be confirmed in later releases
+        # Related GitHub issue: https://github.com/catchorg/Catch2/issues/2417
         set_target_properties(Catch2 PROPERTIES DEBUG_POSTFIX "")
         set_target_properties(Catch2 PROPERTIES EXCLUDE_FROM_ALL "true")
         set_target_properties(Catch2WithMain PROPERTIES EXCLUDE_FROM_ALL "true")
@@ -398,7 +419,7 @@ endif()
 
 if(EIVE_ADD_ETL_LIB)
     target_link_libraries(${LIB_EIVE_MISSION} PUBLIC
-        etl
+        ${LIB_ETL_TARGET}
     )
 endif()