Dont crash when element/target-collector is None

[Tontyna]

Concerning compute_attr_function(): Why not return the fallback?

Concerning _content_list(): target_collector is None when called in @page context. Not shure whether the spec forbids target-* in that context. In any case: Since all the anchors are already collected when we hit compute() within the page margins, no harm is done by not calling target_collector.collect_computed_target(). A css like that works as expected:

@page {
  @top-center {
    content: "countervalue at #id: " target-counter("#id", countername);
  }

That is: Page margins gain access to targets in the document without a detour via string-set/string(). OMG, I fear thats not allowed by the spec...

BTW: With your cleanups it's almost a pleasure to read the code 😃

[liZe]

Concerning compute_attr_function(): Why not return the fallback?

Returning some type when the caller is waiting for another type may break the caller. Oh, and I'm pretty sure nobody actually cares!

Page margins gain access to targets in the document without a detour via string-set/string(). OMG, I fear thats not allowed by the spec...

😝

Looks like it's not forbidden.

BTW: With your cleanups it's almost a pleasure to read the code

It's not perfect but it's much better like this 😉.

One last question: when is computer.element None?

[Tontyna]

Oh, and I'm pretty sure nobody actually cares!

Right you are.

computer.element is None when called (via computed_from_cascaded) by
layout.inlies.first_letter_to_box(), layout.pages.make_margin_boxes.make_box() and formatting_structures.boxes.Box.anonymous_from()