Add necessary find_dependency() to ZNCConfig.cmake

CMakeLists.txt

@@ -79,6 +79,8 @@ macro(tristate_option opt help)
 	endif()
 endmacro()
 
+set(ZNC_CMAKE_FIND_DEPS "")
+
 tristate_option(OPENSSL "Support SSL")
 if(WANT_OPENSSL)
 	find_package(OpenSSL ${TRISTATE_OPENSSL_REQUIRED})
@@ -95,6 +97,8 @@ if(WANT_OPENSSL)
 				HAVE_SSL_SESSION_get0_cipher)
 		endfunction()
 		check_SSL_SESSION_get0_cipher()
+		set(ZNC_CMAKE_FIND_DEPS
+			"${ZNC_CMAKE_FIND_DEPS}\nfind_dependency(OpenSSL)")
 	endif()
 endif()
 set(HAVE_LIBSSL "${OPENSSL_FOUND}")
@@ -146,6 +150,9 @@ if(WANT_ICU)
 	pkg_check_modules(ICU ${TRISTATE_ICU_REQUIRED} IMPORTED_TARGET icu-uc)
 endif()
 set(HAVE_ICU "${ICU_FOUND}")
+if(ICU_FOUND)
+	set(ZNC_CMAKE_FIND_DEPS "${ZNC_CMAKE_FIND_DEPS}\nfind_dependency_pc(ICU icu-uc)")
+endif()
 
 set(WANT_PERL false CACHE BOOL "Support Perl modules")
 set(WANT_PYTHON false CACHE BOOL "Support Python modules")
@@ -421,6 +428,7 @@ include(CMakePackageConfigHelpers)
 write_basic_package_version_file("ZNCConfigVersion.cmake"
 	COMPATIBILITY AnyNewerVersion)
 install(FILES
+	"${PROJECT_SOURCE_DIR}/cmake/CMakeFindDependencyMacroPC.cmake"
 	"${PROJECT_BINARY_DIR}/ZNCConfig.cmake"
 	"${PROJECT_BINARY_DIR}/ZNCConfigVersion.cmake"
 	DESTINATION "${CMAKE_INSTALL_DATADIR}/znc/cmake")

ZNCConfig.cmake.in

@@ -14,6 +14,10 @@
 # limitations under the License.
 #
 
+include(CMakeFindDependencyMacro)
+include("${CMAKE_CURRENT_LIST_DIR}/CMakeFindDependencyMacroPC.cmake")
+@ZNC_CMAKE_FIND_DEPS@
+
 include("${CMAKE_CURRENT_LIST_DIR}/znc_internal.cmake")
 include("${CMAKE_CURRENT_LIST_DIR}/znc_public.cmake")
 include(CMakeParseArguments)

cmake/CMakeFindDependencyMacroPC.cmake

@@ -0,0 +1,99 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+CMakeFindDependencyMacro
+------------------------
+
+.. command:: find_dependency
+
+  The ``find_dependency()`` macro wraps a :command:`find_package` call for
+  a package dependency::
+
+    find_dependency(<dep> [...])
+
+  It is designed to be used in a
+  :ref:`Package Configuration File <Config File Packages>`
+  (``<PackageName>Config.cmake``).  ``find_dependency`` forwards the correct
+  parameters for ``QUIET`` and ``REQUIRED`` which were passed to
+  the original :command:`find_package` call.  Any additional arguments
+  specified are forwarded to :command:`find_package`.
+
+  If the dependency could not be found it sets an informative diagnostic
+  message and calls :command:`return` to end processing of the calling
+  package configuration file and return to the :command:`find_package`
+  command that loaded it.
+
+  .. note::
+
+    The call to :command:`return` makes this macro unsuitable to call
+    from :ref:`Find Modules`.
+
+Package Dependency Search Optimizations
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If ``find_dependency`` is called with arguments identical to a previous
+call in the same directory, perhaps due to diamond-shaped package
+dependencies, the underlying call to :command:`find_package` is optimized
+out.  This optimization is important to support large package dependency
+graphs while avoiding a combinatorial explosion of repeated searches.
+However, the heuristic cannot account for ambient variables that
+affect package behavior, such as ``<PackageName>_USE_STATIC_LIBS``,
+offered by some packages.  Therefore package configuration files should
+avoid setting such variables before their calls to ``find_dependency``.
+
+.. versionchanged:: 3.15
+  Previously, the underlying call to :command:`find_package` was always
+  optimized out if the package had already been found.  CMake 3.15
+  removed the optimization to support cases in which ``find_dependency``
+  call arguments request different components.
+
+.. versionchanged:: 3.26
+  The pre-3.15 optimization was restored, but with the above-described
+  heuristic to account for varying ``find_dependency`` call arguments.
+
+#]=======================================================================]
+
+macro(find_dependency_pc dep)
+find_dependency(PkgConfig)
+  string(SHA256 cmake_fd_call_hash "${dep};${ARGN};${${CMAKE_FIND_PACKAGE_NAME}_FIND_REQUIRED}")
+  if(_CMAKE_${dep}_${cmake_fd_call_hash}_FOUND)
+    unset(cmake_fd_call_hash)
+  else()
+    list(APPEND _CMAKE_${dep}_HASH_STACK ${cmake_fd_call_hash})
+    set(cmake_fd_quiet_arg)
+    if(${CMAKE_FIND_PACKAGE_NAME}_FIND_QUIETLY)
+      set(cmake_fd_quiet_arg QUIET)
+    endif()
+    set(cmake_fd_required_arg)
+    if(${CMAKE_FIND_PACKAGE_NAME}_FIND_REQUIRED)
+      set(cmake_fd_required_arg REQUIRED)
+    endif()
+
+    get_property(cmake_fd_alreadyTransitive GLOBAL PROPERTY
+      _CMAKE_${dep}_TRANSITIVE_DEPENDENCY
+      )
+
+    pkg_check_modules(${dep}
+      ${cmake_fd_quiet_arg}
+      ${cmake_fd_required_arg}
+      IMPORTED_TARGET ${ARGN}
+      )
+    list(POP_BACK _CMAKE_${dep}_HASH_STACK cmake_fd_call_hash)
+    set("_CMAKE_${dep}_${cmake_fd_call_hash}_FOUND" "${${dep}_FOUND}")
+
+    if(NOT DEFINED cmake_fd_alreadyTransitive OR cmake_fd_alreadyTransitive)
+      set_property(GLOBAL PROPERTY _CMAKE_${dep}_TRANSITIVE_DEPENDENCY TRUE)
+    endif()
+
+    unset(cmake_fd_alreadyTransitive)
+    unset(cmake_fd_call_hash)
+    unset(cmake_fd_quiet_arg)
+    unset(cmake_fd_required_arg)
+    if (NOT ${dep}_FOUND)
+      set(${CMAKE_FIND_PACKAGE_NAME}_NOT_FOUND_MESSAGE "${CMAKE_FIND_PACKAGE_NAME} could not be found because dependency ${dep} could not be found.")
+      set(${CMAKE_FIND_PACKAGE_NAME}_FOUND False)
+      return()
+    endif()
+  endif()
+endmacro()