Writing an aspect that traverses _all_ dependency attributes

[bd-tkoolen]

The file count example in the aspect documentation shows how to collect information from dependencies that are listed specifically in a srcs attribute. But what is the best way to visit all dependency attributes, regardless of their name and type?

So far, the only "generic" way of visiting all dependency attribute labels (in attr.label_lists, attr.labels, attr.label_keyed_string_dicts, and attr.string_keyed_label_dicts) I found is:

def _my_aspect_impl(target, ctx):
    def maybe_process_dep(maybe_dep):
        if type(maybe_dep) == "Target":
            # Query `maybe_dep`'s providers...
            pass

    for field in dir(ctx.rule.attr):
        attr = getattr(ctx.rule.attr, field)
        if type(attr) == "list":
            for x in attr:
                maybe_process_dep(x)
        elif type(attr) == "dict":
            for k, v in attr.items():
                maybe_process_dep(k)
                maybe_process_dep(v)
        else:
            maybe_process_dep(attr)

But this is rather messy. Is there a better way to visit all of the target's dependency attribute labels in an aspect?