Linking with Conan targets only when they exists (resolves #98)

example/CMakeLists.txt

@@ -38,6 +38,9 @@ add_example(kalman_filter-alpha_beta_filter_example2)
 
 conan_check_testing(linear_algebra)
 add_example(linear_algebra)
-target_link_libraries(linear_algebra PRIVATE CONAN_PKG::linear_algebra)
+target_link_libraries(linear_algebra
+    PRIVATE
+        $<IF:$<TARGET_EXISTS:CONAN_PKG::linear_algebra>, CONAN_PKG::linear_algebra, linear_algebra::linear_algebra>
+)
 
 add_subdirectory(alternative_namespaces)

src/CMakeLists.txt

@@ -55,7 +55,7 @@ add_library(units INTERFACE)
 target_compile_features(units INTERFACE cxx_std_20)
 target_link_libraries(units
     INTERFACE
-        CONAN_PKG::fmt
+        $<IF:$<TARGET_EXISTS:CONAN_PKG::fmt>, CONAN_PKG::fmt, fmt::fmt>
 )
 target_include_directories(units
     INTERFACE
@@ -65,7 +65,7 @@ target_include_directories(units
 if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     target_link_libraries(units
         INTERFACE
-            CONAN_PKG::range-v3
+            $<IF:$<TARGET_EXISTS:CONAN_PKG::range-v3>, CONAN_PKG::range-v3, range-v3::range-v3>
     )
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     target_compile_options(units
@@ -81,7 +81,7 @@ elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
         )
         target_link_libraries(units
             INTERFACE
-                CONAN_PKG::range-v3
+                $<IF:$<TARGET_EXISTS:CONAN_PKG::range-v3>, CONAN_PKG::range-v3, range-v3::range-v3>
         )
     endif()
 endif()

test/metabench/CMakeLists.txt

@@ -26,7 +26,7 @@ function(add_metabench_test target name erb_path range)
     target_compile_features(${target} PUBLIC cxx_std_20)
     target_link_libraries(${target}
         PUBLIC
-            CONAN_PKG::range-v3
+            $<IF:$<TARGET_EXISTS:CONAN_PKG::range-v3>, CONAN_PKG::range-v3, range-v3::range-v3>
     )
     target_compile_options(${target}
         PUBLIC

test/unit_test/runtime/CMakeLists.txt

@@ -33,7 +33,7 @@ add_executable(unit_tests_runtime
 target_link_libraries(unit_tests_runtime
     PRIVATE
         mp::units
-        CONAN_PKG::Catch2
+        $<IF:$<TARGET_EXISTS:CONAN_PKG::Catch2>, CONAN_PKG::Catch2, Catch2::Catch2>
 )
 
 include(lib/cmake/Catch2/Catch)