FindPkgConfig: Allow libraries that can't be found with their full path

pkg-config's .pc files can sometimes provide libraries that are visible to
the linker but not present in CMake's known search paths.  In the case
where CMake can find some, but not all of the library dependencies
provided in a .pc file, this allows them to be passed through as "-lfoo"
when the full path can't be found.

This also removes the test failure cases that occured because of this
scenario and adjsuts the remaining tests to account for not-found
libraries

2 files changed, 21 insertions, 34 deletions

diff --git a/Modules/FindPkgConfig.cmake b/Modules/FindPkgConfig.cmake
index 4c9af91..5162a44 100644
--- a/Modules/FindPkgConfig.cmake
+++ b/Modules/FindPkgConfig.cmake
@@ -214,7 +214,11 @@ function(_pkg_find_libs _prefix _no_cmake_path _no_cmake_environment_path)
                  NAMES ${_pkg_search}
                  ${_find_opts})
     mark_as_advanced(pkgcfg_lib_${_prefix}_${_pkg_search})
-    list(APPEND _libs "${pkgcfg_lib_${_prefix}_${_pkg_search}}")
+    if(pkgcfg_lib_${_prefix}_${_pkg_search})
+      list(APPEND _libs "${pkgcfg_lib_${_prefix}_${_pkg_search}}")
+    else()
+      list(APPEND _libs ${_pkg_search})
+    endif()
   endforeach()
 
   set(${_prefix}_LINK_LIBRARIES "${_libs}" PARENT_SCOPE)
diff --git a/Tests/RunCMake/FindPkgConfig/FindPkgConfig_IMPORTED_TARGET.cmake b/Tests/RunCMake/FindPkgConfig/FindPkgConfig_IMPORTED_TARGET.cmake
index e82b05f..62bb5de 100644
--- a/Tests/RunCMake/FindPkgConfig/FindPkgConfig_IMPORTED_TARGET.cmake
+++ b/Tests/RunCMake/FindPkgConfig/FindPkgConfig_IMPORTED_TARGET.cmake
@@ -39,7 +39,7 @@ foreach(i 1 2)
 "Name: CMakeInternalFakePackage${i}
 Description: Dummy package (${i}) for FindPkgConfig IMPORTED_TARGET test
 Version: 1.2.3
-Libs: -l${pname}
+Libs: -l${pname} -l${pname}-doesnotexist
 ")
 endforeach()
 
@@ -47,27 +47,6 @@ endforeach()
 # the import target find_library() calls handle the NO...PATH options correctly
 set(ENV{PKG_CONFIG_PATH} ${fakePkgDir}/lib/pkgconfig)
 
-# Confirm correct behavior of NO_CMAKE_PATH, ensuring we only find the library
-# for the imported target if we have both set CMAKE_PREFIX_PATH and have not
-# given the NO_CMAKE_PATH option
-unset(CMAKE_PREFIX_PATH)
-unset(ENV{CMAKE_PREFIX_PATH})
-pkg_check_modules(FakePackage1 QUIET IMPORTED_TARGET cmakeinternalfakepackage1)
-if (TARGET PkgConfig::FakePackage1)
-  message(FATAL_ERROR "Have import target for fake package 1 with no path prefix")
-endif()
-
-set(CMAKE_PREFIX_PATH ${fakePkgDir})
-pkg_check_modules(FakePackage1 QUIET IMPORTED_TARGET NO_CMAKE_PATH cmakeinternalfakepackage1)
-if (TARGET PkgConfig::FakePackage1)
-  message(FATAL_ERROR "Have import target for fake package 1 with ignored cmake path")
-endif()
-
-pkg_check_modules(FakePackage1 REQUIRED QUIET IMPORTED_TARGET cmakeinternalfakepackage1)
-if (NOT TARGET PkgConfig::FakePackage1)
-  message(FATAL_ERROR "No import target for fake package 1 with prefix path")
-endif()
-
 # find targets in subdir and check their visibility
 add_subdirectory(target_subdir)
 if (TARGET PkgConfig::FakePackage1_dir)
@@ -82,31 +61,35 @@ endif()
 # combination
 unset(CMAKE_PREFIX_PATH)
 unset(ENV{CMAKE_PREFIX_PATH})
-pkg_check_modules(FakePackage2 QUIET IMPORTED_TARGET cmakeinternalfakepackage2)
-if (TARGET PkgConfig::FakePackage2)
-  message(FATAL_ERROR "Have import target for fake package 2 with no path prefix")
-endif()
-
 set(ENV{CMAKE_PREFIX_PATH} ${fakePkgDir})
-pkg_check_modules(FakePackage2 QUIET IMPORTED_TARGET NO_CMAKE_ENVIRONMENT_PATH cmakeinternalfakepackage2)
-if (TARGET PkgConfig::FakePackage2)
-  message(FATAL_ERROR "Have import target for fake package 2 with ignored cmake path")
-endif()
 
 pkg_check_modules(FakePackage2 REQUIRED QUIET IMPORTED_TARGET cmakeinternalfakepackage2)
 if (NOT TARGET PkgConfig::FakePackage2)
   message(FATAL_ERROR "No import target for fake package 2 with prefix path")
 endif()
 
+# check that 2 library entries exist
+list(LENGTH FakePackage2_LINK_LIBRARIES fp2_nlibs)
+if (NOT fp2_nlibs EQUAL 2)
+  message(FATAL_ERROR "FakePackage2_LINK_LIBRARIES has ${fp2_nlibs} entries but should have exactly 2")
+endif()
+
 # check that the full library path is also returned
-if (NOT FakePackage2_LINK_LIBRARIES STREQUAL "${fakePkgDir}/lib/libcmakeinternalfakepackage2.a")
+list(GET FakePackage2_LINK_LIBRARIES 0 fp2_lib0)
+if (NOT fp2_lib0 STREQUAL "${fakePkgDir}/lib/libcmakeinternalfakepackage2.a")
+  message(FATAL_ERROR "FakePackage2_LINK_LIBRARIES has bad content on first run: ${FakePackage2_LINK_LIBRARIES}")
+endif()
+
+# check that the library that couldn't be found still shows up
+list(GET FakePackage2_LINK_LIBRARIES 1 fp2_lib1)
+if (NOT fp2_lib1 STREQUAL "cmakeinternalfakepackage2-doesnotexist")
   message(FATAL_ERROR "FakePackage2_LINK_LIBRARIES has bad content on first run: ${FakePackage2_LINK_LIBRARIES}")
 endif()
 
 # the information in *_LINK_LIBRARIES is not cached, so ensure is also is present on second run
 unset(FakePackage2_LINK_LIBRARIES)
 pkg_check_modules(FakePackage2 REQUIRED QUIET IMPORTED_TARGET cmakeinternalfakepackage2)
-if (NOT FakePackage2_LINK_LIBRARIES STREQUAL "${fakePkgDir}/lib/libcmakeinternalfakepackage2.a")
+if (NOT FakePackage2_LINK_LIBRARIES STREQUAL "${fakePkgDir}/lib/libcmakeinternalfakepackage2.a;cmakeinternalfakepackage2-doesnotexist")
   message(FATAL_ERROR "FakePackage2_LINK_LIBRARIES has bad content on second run: ${FakePackage2_LINK_LIBRARIES}")
 endif()