UseJava: enable exportation of native headers target

Help/release/dev/Java-export-native_headers-target.rst

@@ -0,0 +1,6 @@
+Java-export-native_headers-target
+---------------------------------
+
+* ``add_jar()`` command, from :module:`UseJava` module, gains new capabilities
+  for ``GENERATE_NATIVE_HEADERS`` option. These capabilities facilitate the
+  exportation of the generated target.

Modules/UseJava.cmake

@@ -23,7 +23,8 @@ Creating And Installing JARs
           [VERSION <version>]
           [OUTPUT_NAME <name>]
           [OUTPUT_DIR <dir>]
-          [GENERATE_NATIVE_HEADERS <target> [DESTINATION <dir>]]
+          [GENERATE_NATIVE_HEADERS <target>
+                             [DESTINATION (<dir>|INSTALL <dir> [BUILD <dir>])]]
           )
 
 This command creates a ``<target_name>.jar``.  It compiles the given
@@ -37,7 +38,7 @@ For backwards compatibility, jar files listed as sources are ignored (as
 they have been since the first version of this module).
 
 .. versionadded:: 3.4
-  Support fot response files (prefixed by ``@``) in the ``SOURCES`` list.
+  Support for response files (prefixed by ``@``) in the ``SOURCES`` list.
 
 The default ``OUTPUT_DIR`` can also be changed by setting the variable
 ``CMAKE_JAVA_TARGET_OUTPUT_DIR``.
@@ -52,6 +53,12 @@ The default ``OUTPUT_DIR`` can also be changed by setting the variable
 
   ``GENERATE_NATIVE_HEADERS`` option requires, at least, version 1.8 of the JDK.
 
+.. versionadded:: 3.20
+  ``DESTINATION`` sub-option now supports the possibility to specify different
+  output directories for ``BUILD`` and ``INSTALL`` steps. This is required to
+  export the interface target generated by ``GENERATE_NATIVE_HEADERS`` option.
+  If ``BUILD`` directory is not specified, a default directory will be used.
+
 The ``add_jar()`` function sets the following target properties on
 ``<target_name>``:
 
@@ -66,6 +73,11 @@ The ``add_jar()`` function sets the following target properties on
   The directory where the class files can be found.  For example to use them
   with ``javah``.
 
+.. versionadded:: 3.20
+  The target generated by option ``GENERATE_NATIVE_HEADERS`` has the property
+  ``NATIVE_HEADERS_DIRECTORY`` which specify the directory holding the native
+  headers.
+
 .. code-block:: cmake
 
  install_jar(<target_name> <destination>)
@@ -217,6 +229,18 @@ native headers can then be used to compile C/C++ sources with the
   add_library(bar bar.cpp)
   target_link_libraries(bar PRIVATE foo-native)
 
+.. versionadded:: 3.20
+  It is now possible to export the target generated by
+  ``GENERATE_NATIVE_HEADERS`` option.
+
+  .. code-block:: cmake
+
+    add_jar(foo foo.java GENERATE_NATIVE_HEADERS foo-native
+                                                 DESTINATION INSTALL include)
+    install(TARGETS foo-native EXPORT native)
+    install(DIRECTORY "$<TARGET_PROPERTY:foo-native,NATIVE_HEADERS_DIRECTORY>/"
+            DESTINATION include)
+    install(EXPORT native DESTINATION /to/export NAMESPACE foo)
 
 Finding JARs
 ^^^^^^^^^^^^
@@ -493,7 +517,10 @@ function(add_jar _TARGET_NAME)
       if (Java_VERSION VERSION_LESS 1.8)
         message (FATAL_ERROR "ADD_JAR: GENERATE_NATIVE_HEADERS is not supported with this version of Java.")
       endif()
-      cmake_parse_arguments (_add_jar_GENERATE_NATIVE_HEADERS "" "DESTINATION" "" ${_add_jar_GENERATE_NATIVE_HEADERS})
+
+      unset (_GENERATE_NATIVE_HEADERS_OUTPUT_DESC)
+
+      cmake_parse_arguments (_add_jar_GENERATE_NATIVE_HEADERS "" "" "DESTINATION" ${_add_jar_GENERATE_NATIVE_HEADERS})
       if (NOT _add_jar_GENERATE_NATIVE_HEADERS_UNPARSED_ARGUMENTS)
         message (FATAL_ERROR "ADD_JAR: GENERATE_NATIVE_HEADERS: missing required argument.")
       endif()
@@ -504,11 +531,30 @@ function(add_jar _TARGET_NAME)
       endif()
       if (NOT _add_jar_GENERATE_NATIVE_HEADERS_DESTINATION)
         set (_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/${_TARGET_NAME}.dir/native_headers")
+      else()
+        list (LENGTH _add_jar_GENERATE_NATIVE_HEADERS_DESTINATION length)
+        if (NOT length EQUAL 1)
+          cmake_parse_arguments (_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION "" "BUILD;INSTALL" "" "${_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION}")
+          if (_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_UNPARSED_ARGUMENTS)
+            message (FATAL_ERROR "ADD_JAR: GENERATE_NATIVE_HEADERS: DESTINATION: ${_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_UNPARSED_ARGUMENTS}: unexpected argument(s).")
+          endif()
+          if (NOT _add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_INSTALL)
+            message (FATAL_ERROR "ADD_JAR: GENERATE_NATIVE_HEADERS: DESTINATION: INSTALL sub-option is required.")
+          endif()
+          if (NOT _add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_BUILD)
+            set(_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_BUILD "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/${_TARGET_NAME}.dir/native_headers")
+          endif()
+          set(_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION "${_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_BUILD}")
+          set(_GENERATE_NATIVE_HEADERS_OUTPUT_DESC "$<BUILD_INTERFACE:${_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_BUILD}>" "$<INSTALL_INTERFACE:${_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION_INSTALL}>")
+        endif()
       endif()
 
       set (_GENERATE_NATIVE_HEADERS_TARGET ${_add_jar_GENERATE_NATIVE_HEADERS_UNPARSED_ARGUMENTS})
       set (_GENERATE_NATIVE_HEADERS_OUTPUT_DIR "${_add_jar_GENERATE_NATIVE_HEADERS_DESTINATION}")
       set (_GENERATE_NATIVE_HEADERS -h "${_GENERATE_NATIVE_HEADERS_OUTPUT_DIR}")
+      if(NOT _GENERATE_NATIVE_HEADERS_OUTPUT_DESC)
+        set(_GENERATE_NATIVE_HEADERS_OUTPUT_DESC "${_GENERATE_NATIVE_HEADERS_OUTPUT_DIR}")
+      endif()
     endif()
 
     if (LIBRARY_OUTPUT_PATH)
@@ -762,8 +808,9 @@ function(add_jar _TARGET_NAME)
     # create an INTERFACE library encapsulating include directory for generated headers
     add_library (${_GENERATE_NATIVE_HEADERS_TARGET} INTERFACE)
     target_include_directories (${_GENERATE_NATIVE_HEADERS_TARGET} INTERFACE
-      "${_GENERATE_NATIVE_HEADERS_OUTPUT_DIR}"
+      "${_GENERATE_NATIVE_HEADERS_OUTPUT_DESC}"
       ${JNI_INCLUDE_DIRS})
+    set_property(TARGET ${_GENERATE_NATIVE_HEADERS_TARGET} PROPERTY NATIVE_HEADERS_DIRECTORY "${_GENERATE_NATIVE_HEADERS_OUTPUT_DIR}")
     # this INTERFACE library depends on jar generation
     add_dependencies (${_GENERATE_NATIVE_HEADERS_TARGET} ${_TARGET_NAME})
 

Tests/CMakeLists.txt

@@ -3394,6 +3394,9 @@ if(BUILD_TESTING)
               ${build_generator_args}
               --build-project helloJavaNativeHeaders
               --build-run-dir "${CMake_BINARY_DIR}/Tests/JavaNativeHeaders/"
+              --build-target install
+              --build-options
+              "-DCMAKE_INSTALL_PREFIX:PATH=${CMake_BINARY_DIR}/Tests/JavaNativeHeaders/Install"
               --test-command ${CMAKE_CTEST_COMMAND} -V -C $<CONFIG>)
             list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/JavaNativeHeaders")
           endif()

Tests/JavaNativeHeaders/CMakeLists.txt

@@ -11,7 +11,7 @@ include (UseJava)
 # JNI support
 find_package(JNI)
 
-add_jar(B1 D.java GENERATE_NATIVE_HEADERS D1-native)
+add_jar(B1 D.java GENERATE_NATIVE_HEADERS D1-native DESTINATION INSTALL include)
 add_jar(E1 E.java GENERATE_NATIVE_HEADERS E1-native)
 
 add_jar(hello4 HelloWorld3.java)
@@ -19,6 +19,13 @@ add_jar(hello4 HelloWorld3.java)
 add_library(D SHARED D.cpp E.cpp)
 target_link_libraries (D PRIVATE D1-native E1-native)
 
+install(TARGETS D1-native EXPORT native)
+install(DIRECTORY "$<TARGET_PROPERTY:D1-native,NATIVE_HEADERS_DIRECTORY>/" DESTINATION include)
+install(EXPORT native DESTINATION "${CMAKE_INSTALL_PREFIX}" NAMESPACE D1::)
+
 
 add_test (NAME Java.NativeHeaders
           COMMAND "${Java_JAVA_EXECUTABLE}" -Djava.library.path=$<TARGET_FILE_DIR:D> -classpath hello4.jar HelloWorld3)
+
+add_test (NAME Java.ImportNativeHeaders
+          COMMAND "${CMAKE_COMMAND}" "-DNATIVE_HEADERS_IMPORT_DIR=${CMAKE_INSTALL_PREFIX}" -S "${CMAKE_CURRENT_SOURCE_DIR}/Import" -B "${CMAKE_CURRENT_BINARY_DIR}/Import")

Tests/JavaNativeHeaders/Import/CMakeLists.txt

@@ -0,0 +1,19 @@
+project(ImportJavaNativeHeaders LANGUAGES NONE)
+
+cmake_minimum_required (VERSION 3.19...3.20)
+set(CMAKE_VERBOSE_MAKEFILE 1)
+
+include(${NATIVE_HEADERS_IMPORT_DIR}/native.cmake)
+
+if(NOT TARGET D1::D1-native)
+  message(FATAL_ERROR "Target 'D1::D1-native' not found.")
+endif()
+
+get_property(incs TARGET D1::D1-native PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
+if (NOT incs MATCHES "${NATIVE_HEADERS_IMPORT_DIR}/include")
+  message(FATAL_ERROR "Target 'D1::D1-native', property 'INTERFACE_INCLUDE_DIRECTORIES' badly defined: ${incs}.")
+endif()
+
+if (NOT EXISTS "${NATIVE_HEADERS_IMPORT_DIR}/include/D.h")
+  message(FATAL_ERROR "file '${NATIVE_HEADERS_IMPORT_DIR}/include/D.h' not found.")
+endif()