FindPkgConfig: support also > and < operators for version compares

Fixes: #18416

Help/release/3.13.rst

@@ -157,6 +157,10 @@ Modules
 * The :module:`FindPkgConfig` module gained an option to create imported
   targets in global scope.
 
+* The :module:`FindPkgConfig` module gained support for ``<`` and ``>``
+  operators for version checks in addition to the already supported
+  operators ``>=``, ``<=``, and ``=``.
+
 * Modules :module:`FindPython3`, :module:`FindPython2` and :module:`FindPython`
   gain capability to control order of resource lookup on macOS (Framework) and
   Windows (Registry).

Modules/FindPkgConfig.cmake

@@ -397,7 +397,7 @@ macro(_pkg_check_modules_internal _is_required _is_silent _no_cmake_path _no_cma
       set(_pkg_check_modules_exist_query)
 
       # check whether version is given
-      if (_pkg_check_modules_pkg MATCHES "(.*[^><])(>=|=|<=)(.*)")
+      if (_pkg_check_modules_pkg MATCHES "(.*[^><])(=|[><]=?)(.*)")
         set(_pkg_check_modules_pkg_name "${CMAKE_MATCH_1}")
         set(_pkg_check_modules_pkg_op "${CMAKE_MATCH_2}")
         set(_pkg_check_modules_pkg_ver "${CMAKE_MATCH_3}")
@@ -415,9 +415,11 @@ macro(_pkg_check_modules_internal _is_required _is_silent _no_cmake_path _no_cma
       list(APPEND _pkg_check_modules_packages    "${_pkg_check_modules_pkg_name}")
 
       # create the final query which is of the format:
+      # * <pkg-name> > <version>
       # * <pkg-name> >= <version>
       # * <pkg-name> = <version>
       # * <pkg-name> <= <version>
+      # * <pkg-name> < <version>
       # * --exists <pkg-name>
       list(APPEND _pkg_check_modules_exist_query --print-errors --short-errors)
       if (_pkg_check_modules_pkg_op)

Tests/RunCMake/FindPkgConfig/FindPkgConfig_VERSION_OPERATORS.cmake

@@ -0,0 +1,83 @@
+cmake_minimum_required(VERSION 3.12)
+
+project(FindPkgConfig_IMPORTED_TARGET C)
+
+find_package(PkgConfig REQUIRED)
+
+message(STATUS "source: ${CMAKE_CURRENT_SOURCE_DIR} bin ${CMAKE_CURRENT_BINARY_DIR}")
+
+# Setup for the remaining package tests below
+set(PKG_CONFIG_USE_CMAKE_PREFIX_PATH)
+set(fakePkgDir ${CMAKE_CURRENT_BINARY_DIR}/pc-fakepackage)
+file(WRITE ${fakePkgDir}/lib/libcmakeinternalfakepackage.a "")
+file(WRITE ${fakePkgDir}/lib/cmakeinternalfakepackage.lib  "")
+file(WRITE ${fakePkgDir}/lib/pkgconfig/cmakeinternalfakepackage.pc
+"Name: CMakeInternalFakePackage
+Description: Dummy package for FindPkgConfig VERSION_OPERATORS test
+Version: 8.9
+Libs: -lcmakeinternalfakepackage
+")
+
+# Always find the .pc file in the calls further below so that we can test that
+# the import target find_library() calls handle the NO...PATH options correctly
+set(ENV{PKG_CONFIG_PATH} ${fakePkgDir}/lib/pkgconfig)
+
+pkg_check_modules(FakePackageGE REQUIRED QUIET "cmakeinternalfakepackage >= 8")
+if (NOT FakePackageGE_FOUND)
+  message(FATAL_ERROR "fake package >= 8 not found")
+endif()
+
+pkg_check_modules(FakePackageGE_FAIL QUIET "cmakeinternalfakepackage >= 8.10")
+if (FakePackageGE_FAIL_FOUND)
+  message(FATAL_ERROR "fake package >= 8.10 found")
+endif()
+
+pkg_check_modules(FakePackageLE REQUIRED QUIET "cmakeinternalfakepackage<=9")
+if (NOT FakePackageLE_FOUND)
+  message(FATAL_ERROR "fake package <= 9 not found")
+endif()
+
+pkg_check_modules(FakePackageLE_FAIL QUIET "cmakeinternalfakepackage <= 8.1")
+if (FakePackageLE_FAIL_FOUND)
+  message(FATAL_ERROR "fake package <= 8.1 found")
+endif()
+
+pkg_check_modules(FakePackageGT REQUIRED QUIET "cmakeinternalfakepackage > 8")
+if (NOT FakePackageGT_FOUND)
+  message(FATAL_ERROR "fake package > 8 not found")
+endif()
+
+pkg_check_modules(FakePackageGT_FAIL QUIET "cmakeinternalfakepackage > 8.9")
+if (FakePackageGT_FAIL_FOUND)
+  message(FATAL_ERROR "fake package > 8.9 found")
+endif()
+
+pkg_check_modules(FakePackageLT REQUIRED QUIET "cmakeinternalfakepackage<9")
+if (NOT FakePackageLT_FOUND)
+  message(FATAL_ERROR "fake package < 9 not found")
+endif()
+
+pkg_check_modules(FakePackageLT_FAIL QUIET "cmakeinternalfakepackage < 8.9")
+if (FakePackageLT_FAIL_FOUND)
+  message(FATAL_ERROR "fake package < 8.9 found")
+endif()
+
+pkg_check_modules(FakePackageEQ REQUIRED QUIET "cmakeinternalfakepackage=8.9")
+if (NOT FakePackageEQ_FOUND)
+  message(FATAL_ERROR "fake package = 8.9 not found")
+endif()
+
+pkg_check_modules(FakePackageEQ_FAIL QUIET "cmakeinternalfakepackage = 8.8")
+if (FakePackageEQ_FAIL_FOUND)
+  message(FATAL_ERROR "fake package = 8.8 found")
+endif()
+
+pkg_check_modules(FakePackageEQ_INV QUIET "cmakeinternalfakepackage == 8.9")
+if (FakePackageEQ_FAIL_FOUND)
+  message(FATAL_ERROR "fake package == 8.9 found")
+endif()
+
+pkg_check_modules(FakePackageLLT_INV QUIET "cmakeinternalfakepackage <<= 9")
+if (FakePackageLLT_FAIL_FOUND)
+  message(FATAL_ERROR "fake package <<= 9 found")
+endif()

Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake

@@ -16,4 +16,5 @@ if (PKG_CONFIG_FOUND)
   run_cmake(FindPkgConfig_GET_VARIABLE)
   run_cmake(FindPkgConfig_cache_variables)
   run_cmake(FindPkgConfig_IMPORTED_TARGET)
+  run_cmake(FindPkgConfig_VERSION_OPERATORS)
 endif ()