Container method to get routine by name

[sergisiso]

While doing #2739 some PSyKAl transformation scripts have:

invoke = psy.invokes.get("invoke_propagate_perturbation")
schedule invoke.schedule
# Modify schedule

With the new transformation signature this needs to be updated to:

for subroutine in psyir.walk(Routine):
    if subroutine.name == "invoke_propagate_perturbation":
        # Modify subroutine

Which I am not totally satisfied because it is more verbose, adds indentations, and even worst, it doesn't fail if the named routine does not exist. It would be good to add a generic Conatiner.get method to get routines by name or fail:

subroutine = psyir.children.get("invoke_propagate_perturbation")
# Modify subroutine

The first 'children' is unrelated, it is for going to the FileContainer to the Module also introduced in the mentioned PR.

Some alternatives are:

subroutine = psyir.children.routine("invoke_propagate_perturbation")
subroutine = psyir.children["invoke_propagate_perturbation"]

[sergisiso]

Currently I can also do:

name = "invoke_propagate_perturbation"
subroutine = [x for x in psyir.children[0].children if x.name == name][0]

[arporter]

Container currently has resolve_routine(name) and find_routine_psyir(name). Are these what you want (possibly with a nicer name for the last one)?

[sergisiso]

Those methods implement all the 'language' knowledge regarding visibility, imports, interfaces, ... I was thinking something simpler, something akin to the tree semantic navigation methods that we have, so that we can navigate the tree by name when it makes sense.

E.g. "go to the lhs of the 3rd statement of the "mysub" routine in the first module" would be:
target = psyir[0]["mysub"][2].lhs

Note that in this example I navigate 2 container, one by index-order [0] and one by name ["mysub"]. But I am just traversing the tree, I am not interested in language logic here.