fix(packaging): reuse provided dependency targets

.github/workflows/ci.yml

@@ -65,6 +65,23 @@ jobs:
       - name: Build fmt-enabled consumer project
         if: matrix.std == 17
         run: cmake --build build-fmt-consumer
+      - name: Configure build-tree dependency reuse
+        if: matrix.std == 17
+        run: >-
+          cmake -S tests/dependency_reuse/build_tree -B build-timeshield-reuse
+          -DLOGIT_SOURCE_DIR=${{ github.workspace }}
+          -DCMAKE_DISABLE_FIND_PACKAGE_TimeShield=TRUE
+      - name: Configure installed dependency reuse
+        if: matrix.std == 17
+        run: >-
+          cmake -S tests/dependency_reuse/installed -B build-installed-reuse
+          -DLOGIT_SOURCE_DIR=${{ github.workspace }}
+          -DCMAKE_PREFIX_PATH=${{ github.workspace }}/install-fmt-package
+          -DCMAKE_DISABLE_FIND_PACKAGE_TimeShield=TRUE
+          -DCMAKE_DISABLE_FIND_PACKAGE_fmt=TRUE
+      - name: Build installed dependency reuse
+        if: matrix.std == 17
+        run: cmake --build build-installed-reuse
       - name: Configure Prometheus server package
         if: matrix.std == 17
         run: cmake -S . -B build-prometheus-package -DLOGIT_CPP_BUILD_TESTS=OFF -DLOGIT_WITH_PROMETHEUS_SERVER=ON -DLOGIT_WITH_SYSLOG=OFF -DLOGIT_WITH_WIN_EVENT_LOG=OFF

CMakeLists.txt

@@ -37,8 +37,10 @@ if(LOGIT_WITH_MDBX AND CMAKE_CXX_STANDARD LESS 17)
 endif()
 
 # Dependency: TimeShield
-find_package(TimeShield 1.0.6 QUIET CONFIG)
-if(NOT TimeShield_FOUND)
+if(NOT TARGET time_shield::time_shield)
+    find_package(TimeShield 1.0.6 QUIET CONFIG)
+endif()
+if(NOT TARGET time_shield::time_shield)
     if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/external/time-shield-cpp/CMakeLists.txt")
         add_subdirectory(external/time-shield-cpp)
     else()

cmake/log-it-cppConfig.cmake.in

@@ -1,25 +1,27 @@
 @PACKAGE_INIT@
 
 include(CMakeFindDependencyMacro)
-find_dependency(TimeShield)
+if(NOT TARGET time_shield::time_shield)
+    find_dependency(TimeShield 1.0.6 CONFIG)
+endif()
 
-if(@LOGIT_WITH_FMT@)
+if(@LOGIT_WITH_FMT@ AND NOT TARGET fmt::fmt)
     find_dependency(fmt CONFIG)
 endif()
 
-if(@LOGIT_WITH_OTLP@)
+if(@LOGIT_WITH_OTLP@ AND NOT TARGET kurlyk)
     find_dependency(kurlyk CONFIG)
 endif()
 
-if(@LOGIT_WITH_GZIP@)
+if(@LOGIT_WITH_GZIP@ AND NOT TARGET ZLIB::ZLIB)
     find_dependency(ZLIB)
 endif()
 
-if(@LOGIT_WITH_ZSTD@)
+if(@LOGIT_WITH_ZSTD@ AND NOT TARGET ZSTD::ZSTD)
     find_dependency(ZSTD)
 endif()
 
-if(@LOGIT_WITH_MDBX@)
+if(@LOGIT_WITH_MDBX@ AND NOT TARGET mdbx_containers::mdbx_containers)
     find_dependency(mdbx_containers CONFIG)
 endif()
 

tests/dependency_reuse/build_tree/CMakeLists.txt

@@ -0,0 +1,20 @@
+cmake_minimum_required(VERSION 3.18)
+project(parent_provided_timeshield LANGUAGES CXX)
+
+if(NOT DEFINED LOGIT_SOURCE_DIR)
+    message(FATAL_ERROR "LOGIT_SOURCE_DIR must point to the LogIt++ checkout")
+endif()
+if(NOT CMAKE_DISABLE_FIND_PACKAGE_TimeShield)
+    message(FATAL_ERROR "The test must disable TimeShield package discovery")
+endif()
+
+# Model a parent project that has already provided TimeShield. The test invokes
+# CMake with CMAKE_DISABLE_FIND_PACKAGE_TimeShield=TRUE so a regression that
+# probes the package before checking the target cannot fall back silently.
+add_library(time_shield::time_shield INTERFACE IMPORTED GLOBAL)
+
+add_subdirectory("${LOGIT_SOURCE_DIR}" "${CMAKE_CURRENT_BINARY_DIR}/log-it-cpp")
+
+if(NOT TARGET log-it-cpp::log-it-cpp)
+    message(FATAL_ERROR "LogIt++ target was not created")
+endif()

tests/dependency_reuse/installed/CMakeLists.txt

@@ -0,0 +1,31 @@
+cmake_minimum_required(VERSION 3.18)
+project(installed_dependency_reuse LANGUAGES CXX)
+
+if(NOT DEFINED LOGIT_SOURCE_DIR)
+    message(FATAL_ERROR "LOGIT_SOURCE_DIR must point to the LogIt++ checkout")
+endif()
+if(NOT CMAKE_DISABLE_FIND_PACKAGE_TimeShield OR
+   NOT CMAKE_DISABLE_FIND_PACKAGE_fmt)
+    message(FATAL_ERROR "The test must disable TimeShield and fmt package discovery")
+endif()
+
+# Both targets model dependencies supplied by the parent project. Discovery is
+# disabled by the invoking test so the installed package must reuse these
+# targets instead of calling find_dependency().
+add_library(time_shield::time_shield INTERFACE IMPORTED GLOBAL)
+set_target_properties(time_shield::time_shield PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "${LOGIT_SOURCE_DIR}/external/time-shield-cpp/include"
+)
+
+add_library(fmt::fmt INTERFACE IMPORTED GLOBAL)
+set_target_properties(fmt::fmt PROPERTIES
+    INTERFACE_INCLUDE_DIRECTORIES "${LOGIT_SOURCE_DIR}/external/fmt/include"
+)
+
+find_package(log-it-cpp CONFIG REQUIRED)
+
+add_executable(installed_dependency_reuse main.cpp)
+target_link_libraries(installed_dependency_reuse PRIVATE log-it-cpp::log-it-cpp)
+if(MSVC)
+    target_compile_options(installed_dependency_reuse PRIVATE /utf-8)
+endif()

tests/dependency_reuse/installed/main.cpp

@@ -0,0 +1,6 @@
+#include <logit.hpp>
+
+int main() {
+    LOGIT_FMT_INFO("dependency reuse {}", 42);
+    return 0;
+}