CMake: Support legacy EXPAT Find package in the config file

Fix #494

Author: Ghabry

CMakeLists.txt

@@ -389,13 +389,14 @@ if(LIBLCF_WITH_XML)
 	find_package(expat CONFIG)
 	if(expat_FOUND)
 		target_link_libraries(lcf expat::expat)
+		set(LCF_SUPPORT_XML 1)
 	else()
 		# Fallback to old expat detection
 		find_package(EXPAT REQUIRED)
 		target_link_libraries(lcf EXPAT::EXPAT)
+		set(LCF_SUPPORT_XML 2)
 	endif()
 	list(APPEND LIBLCF_DEPS "expat")
-	set(LCF_SUPPORT_XML 1)
 endif()
 
 # mime types

builds/cmake/liblcf-config.cmake.in

@@ -13,8 +13,22 @@ if(@LCF_SUPPORT_ICU@ EQUAL 1)
 	find_dependency(ICU COMPONENTS i18n uc data REQUIRED)
 endif()
 
-if(@LCF_SUPPORT_XML@)
+if(@LCF_SUPPORT_XML@ EQUAL 1)
 	find_dependency(expat CONFIG REQUIRED)
+elseif(@LCF_SUPPORT_XML@ EQUAL 2)
+	# Fallback to old expat detection
+	find_dependency(EXPAT REQUIRED)
+endif()
+
+## Create aliases for common expat target names
+# The config file creates expat::expat
+if (TARGET expat::expat AND NOT TARGET EXPAT::EXPAT)
+	add_library(EXPAT::EXPAT ALIAS expat::expat)
+endif()
+
+# The find module creates EXPAT::EXPAT
+if (TARGET EXPAT::EXPAT AND NOT TARGET expat::expat)
+	add_library(expat::expat ALIAS EXPAT::EXPAT)
 endif()
 
 include(${CMAKE_CURRENT_LIST_DIR}/liblcf-targets.cmake)