There was a logical error in the code. Instead of writing: array1 = array1.concat(array2); ...to append array2 to array1. The code was: array1.concat(array2); ...which does not do anything. As a result, it was impossible to actually use a mixin. This also fixes another issue: colcon lcov-result is failling for packages without coverage info, so we need to pass --packages-select when running it. Signed-off-by: Thomas Moulard <tmoulard@amazon.com>