Remove "abort these steps" wording

[domenic]

In Infra, we have clarified that "return" or "throw" aborts the algorithm it is in. This convention was adopted after much of the prose in the HTML Standard was written, so HTML contains many now-redundant sequences like

then return null and abort these steps

or

then throw a TypeError and abort these steps.

These should remove the redundant "and abort these steps". Similarly, cases like

Otherwise, if the new value is the same as the body element, do nothing. Abort these steps.

should be converted to replace "Abort these steps" with "Return".

Doing so helps set a good example, and reduce confusion for people who read HTML (which is currently a mix of the new style and the old style).

There are currently 427 instances of "abort these steps". If any of them seem tricky, feel free to leave them in and we can take care of them later. Just getting the straightforward ones is a big enough task.

(This is part of #2053)

[sam0410]

Hi @domenic, I added a PR for this #3140. Please review.

[domenic]

Progress! After 7ebc44a, many of these are gone. 71 remain, and some of them are legitimate, e.g. they occur inside "in parallel" steps (for which return/throw don't work).

But others should be replaced, e.g. the one in drawImage() or the ImageData constructor. (ImageData even has a "throw an ... and return"; we should remove the "and return".) So there's still some work to do here.

[shreyateeza]

Hello! I would like to work on this issue. @domenic

[domenic]

Great! Check out https://github.com/whatwg/html/blob/master/CONTRIBUTING.md to get set up. Then, try to find all instances of "abort these steps" and replace them with "return". Some of them need to stay "abort these steps", but we can point those out when you get to them.

[shreyateeza]

@domenic Please assign me for this issue.

[domenic]

@shreyateeza GitHub doesn't let me do that, but no fear, you've stated this issue is yours; nobody else will take it :). You can work on it without being assigned.