Change download flag to CLAP_HELPERS_DOWNLOAD_IF_NEEDED.

Issue a fatal error if clap or catch2 (if needed) targets
are missing and download is off.

.github/workflows/pullreq.yml

@@ -89,7 +89,7 @@ jobs:
 
       - name: Build project
         run: |
-          cmake -S . -B ./build ${{ matrix.cmakeargs }} -DCMAKE_BUILD_TYPE=Debug -DCLAP_HELPERS_BUILD_TESTS=TRUE
+          cmake -S . -B ./build ${{ matrix.cmakeargs }} -DCMAKE_BUILD_TYPE=Debug -DCLAP_HELPERS_DOWNLOAD_IF_NEEDED=TRUE -DCLAP_HELPERS_BUILD_TESTS=TRUE
           cmake --build ./build --config Debug --target clap-helpers-tests --parallel
 
       - name: Run Tests

CMakeLists.txt

@@ -3,12 +3,12 @@ cmake_policy(SET CMP0100 NEW)  # handle .hh files
 project(clap-helpers C CXX)
 
 option(CLAP_HELPERS_BUILD_TESTS "Build tests for the CLAP Helper" FALSE)
-option(CLAP_HELPERS_ALWAYS_DOWNLOAD "Always download CPM versions even if target defined" FALSE)
+option(CLAP_HELPERS_DOWNLOAD_IF_NEEDED "Resolve CLAP Targets with CPM if not defined" FALSE)
 
 add_library(${PROJECT_NAME} INTERFACE)
 target_include_directories(${PROJECT_NAME} INTERFACE include)
 
-if ((NOT TARGET clap) OR ${CLAP_HELPERS_ALWAYS_DOWNLOAD})
+if ((NOT TARGET clap) AND ${CLAP_HELPERS_DOWNLOAD_IF_NEEDED})
     message(STATUS "${PROJECT_NAME}: Downloading CLAP using CPM")
 
     message(STATUS "${PROJECT_NAME}: including CPM")
@@ -23,6 +23,8 @@ if ((NOT TARGET clap) OR ${CLAP_HELPERS_ALWAYS_DOWNLOAD})
     )
 
     add_subdirectory(${CMAKE_BINARY_DIR}/cpm/clap)
+else()
+    message(FATAL_ERROR "${PROJECT_NAME}: 'clap' is not a target. Set CLAP_HELPERS_DOWNLOAD_IF_NEEDED or include clap before clap-helpers")
 endif()
 target_link_libraries(${PROJECT_NAME} INTERFACE clap)
 
@@ -32,7 +34,7 @@ if (${CLAP_HELPERS_BUILD_TESTS})
         set(CLAP_HELPERS_TESTS_CXX_STANDARD 11)
     endif()
 
-    if ((NOT TARGET Catch2::Catch2WithMain) OR ${CLAP_HELPERS_ALWAYS_DOWNLOAD})
+    if ((NOT TARGET Catch2::Catch2WithMain) AND ${CLAP_HELPERS_DOWNLOAD_IF_NEEDED})
         message(STATUS "${PROJECT_NAME}: Downloading Catch2")
         include(cmake/external/CPM.cmake)
         CPMAddPackage(
@@ -44,6 +46,8 @@ if (${CLAP_HELPERS_BUILD_TESTS})
                 SOURCE_DIR cpm/catch2
         )
         add_subdirectory(${CMAKE_BINARY_DIR}/cpm/catch2)
+    else()
+        message(FATAL_ERROR "${PROJECT_NAME}: 'Catch2::Catch2WithMain' is not a target. Set CLAP_HELPERS_DOWNLOAD_IF_NEEDED or include catch2 before clap-helpers")
     endif()
 
     add_executable(${PROJECT_NAME}-tests EXCLUDE_FROM_ALL