Apply refurb/ruff rule FURB142

[DimitriPapadopoulos]

Subject: Apply refurb/ruff rule FURB142

Feature or Bugfix

• Refactoring

Purpose

Fix this issue:

FURB142 Use of `set.add()` in a for loop

Relates

• https://docs.astral.sh/ruff/rules/#refurb-furb
• ruff: Add new refurb (FURB) rules #11834

[chrisjsewell]

Similar to #11849 (comment)

[DimitriPapadopoulos]

Actually FURB142 is available in preview mode:

$ ruff check --select FURB142 --preview
sphinx/builders/__init__.py:317:9: FURB142 [*] Use of `set.add()` in a for loop
    |
315 |           doccount = len(updated_docnames)
316 |           logger.info(bold(__('looking for now-outdated files... ')), nonl=True)
317 |           for docname in self.env.check_dependents(self.app, updated_docnames):
    |  _________^
318 | |             updated_docnames.add(docname)
    | |_________________________________________^ FURB142
319 |           outdated = len(updated_docnames) - doccount
320 |           if outdated:
    |
    = help: Replace with `.update()`

Found 1 error.
[*] 1 fixable with the `--fix` option.
$ 

It should land in standard mode in upcoming versions of ruff. I am applying the rule so that the issue doesn't arise in the future. Additionally, the fix makes total sense.

[chrisjsewell]

Actually FURB142 is available in preview mode

we also have preview=true, its just that it is not available in ruff==0.3.4
We can't update to 0.3.5 yet though, because of astral-sh/ruff#10724, but I'm sure 0.3.6 will be right around the corner 😄