Introduce relocatable AMENT_IMPORT_PREFIX

This moves the logic to compute the install prefix to a single location
in the main config file. Extra config files can use the new
AMENT_IMPORT_PREFIX variable, which simplifies the code and makes it
more robust to future changes.

The logic to compute AMENT_IMPORT_PREFIX has been taken from the
CMakePackageConfigHelpers module. The code is well-tested and also
handles symlink aliasing.

Signed-off-by: Timo Röhling <[email protected]>

Author: roehling

ament_cmake_core/cmake/core/templates/nameConfig.cmake.in

@@ -35,6 +35,18 @@ endif()
 # flag package as ament-based to distinguish it after being find_package()-ed
 set(@PROJECT_NAME@_FOUND_AMENT_PACKAGE TRUE)
 
+# Compute relocatable install prefix. This is pretty much the same code as it
+# is generated by the CMakePackageConfigHelpers module.
+get_filename_component(AMENT_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_DIR}/../../../" ABSOLUTE)
+# Use original install prefix if the package was merely found via symlink alias
+get_filename_component(_realCurr "${CMAKE_CURRENT_LIST_DIR}" REALPATH)
+get_filename_component(_realOrig "@CMAKE_INSTALL_PREFIX@/share/@PROJECT_NAME@/cmake" REALPATH)
+if(_realCurr STREQUAL _realOrig)
+  set(AMENT_IMPORT_PREFIX "@CMAKE_INSTALL_PREFIX@")
+endif()
+unset(_realCurr)
+unset(_realOrig)
+
 # include all config extra files
 set(_extras "@PACKAGE_CONFIG_EXTRA_FILES@")
 foreach(_extra ${_extras})

ament_cmake_export_include_directories/cmake/ament_export_include_directories.cmake

@@ -37,7 +37,7 @@ macro(ament_export_include_directories)
       if(NOT IS_ABSOLUTE "${_arg}")
         # prefix relative paths with CMAKE_INSTALL_PREFIX
         # while avoiding to embed any absolute path
-        set(_arg "\${${PROJECT_NAME}_DIR}/../../../${_arg}")
+        set(_arg "\${AMENT_IMPORT_PREFIX}/${_arg}")
         list_append_unique(_AMENT_EXPORT_RELATIVE_INCLUDE_DIRECTORIES "${_arg}")
       else()
         if(NOT IS_DIRECTORY "${_arg}")

ament_cmake_export_libraries/cmake/ament_cmake_export_libraries-extras.cmake.in

@@ -39,7 +39,7 @@ if(NOT _exported_libraries STREQUAL "")
       set(_lib "NOTFOUND")
       find_library(
         _lib NAMES "${_library}"
-        PATHS "${@PROJECT_NAME@_DIR}/../../../lib"
+        PATHS "${AMENT_IMPORT_PREFIX}/lib"
         NO_DEFAULT_PATH NO_CMAKE_FIND_ROOT_PATH
       )