Rely on target_link_libraries to add include directories

Fixes ros2/ros2#1150

The current solution only orders the declared dependencies (and not their transitive dependencies).
Instead or order the include directories, we can instead order the targets themselves based on a
heuristic that checks if the dependencies are part of the current overlay or not. Dependencies
that are part of the current overlay are prepended to the interface list so that we make sure
to find their include directories before any in an underlay.

Signed-off-by: Jacob Perron <[email protected]>

ament_cmake_target_dependencies/cmake/ament_target_dependencies.cmake

@@ -70,6 +70,7 @@ function(ament_target_dependencies target)
     set(definitions "")
     set(include_dirs "")
     set(interfaces "")
+    set(sorted_interfaces "")
     set(libraries "")
     set(link_flags "")
     foreach(package_name ${ARG_UNPARSED_ARGUMENTS})
@@ -127,23 +128,34 @@ function(ament_target_dependencies target)
     if(NOT ARG_INTERFACE)
       target_compile_definitions(${target}
         ${required_keyword} ${definitions})
-      # the interface include dirs must be ordered
-      set(interface_include_dirs)
+
+      # Order interface to support workspace overlaying
+      # Interfaces built in the same workspace should appear before those in an underlay
+      # This fixes issues related to overlaying on a "merged" workspace, where includes from
+      # multiple packages appear in the same directory
+      set(_install_prefix ${CMAKE_INSTALL_PREFIX})
+      get_filename_component(_install_prefix_parent ${_install_prefix} DIRECTORY)
       foreach(interface ${interfaces})
         get_target_property(_include_dirs ${interface} INTERFACE_INCLUDE_DIRECTORIES)
+        # If include directory has the same parent as the target, then make sure it appears at the
+        # beginning of the list
         if(_include_dirs)
-          list_append_unique(interface_include_dirs ${_include_dirs})
+          # TODO: handle case that _include_dirs is a list
+          if(_include_dirs MATCHES "^${_install_prefix}.*")
+            list(PREPEND sorted_interfaces ${interface})
+          elseif(_include_dirs MATCHES "^${_install_prefix_parent}.*")
+            list(PREPEND sorted_interfaces ${interface})
+          else()
+            list(APPEND sorted_interfaces ${interface})
+          endif()
+        else()
+          list(APPEND sorted_interfaces ${interface})
         endif()
       endforeach()
-      ament_include_directories_order(ordered_interface_include_dirs ${interface_include_dirs})
-      # the interface include dirs are used privately to ensure proper order
-      # and the interfaces cover the public case
-      target_include_directories(${target} ${system_keyword}
-        PRIVATE ${ordered_interface_include_dirs})
     endif()
     ament_include_directories_order(ordered_include_dirs ${include_dirs})
     target_link_libraries(${target}
-      ${optional_keyword} ${interfaces})
+      ${optional_keyword} ${sorted_interfaces})
     target_include_directories(${target} ${system_keyword}
       ${required_keyword} ${ordered_include_dirs})
     if(NOT ARG_INTERFACE)