Dependency tree

package_d -> package_c

package_c -> package_a, package_b

Reproduction steps

To reproduce the dependency issue, build an underlay workspace with --merge-install (That's the default for /opt/ros):

    cd underlay
    colcon build --merge-install

Source the underlay and build the overlay

    source install/setup.bash
    cd ../overlay
    colcon build

Expect a compiler error due to an undeclared function package_a_foo_renamed.

Explanation

package_a exists in both the underlay and overlay, with a modified version in the overlay. package_c depends on the modified version of package_a (in the overlay) and package_b in the underlay. package_d depends on package_c and transitively on package_a and package_b.

When building package_c, its interface dependencies are explicitly sorted.

However, when building package_d, it doesn't report INTERFACE_INCLUDE_DIRECTORIES of transitive dependencies. Thus, the include directories of a and b are not considered for sorting in above-mentioned code, but are used according to the order given in ament_target_dependencies(package_c ...). Indeed, changing the order there would fix the issue.

Solution Proposal

Obviously, sorting of include directories should consider all dependencies. Actually, ament/ament_cmake#259 already implemented a function to recursively retrieve all include dirs. However, ament/ament_cmake#260, which introduced the code above, didn't consider that?!

I was really surprised to hit such a fundamental issue.