style: forbid url do blocks in homebrew/cask

[Rylan12]

Follow-up to #18390

This PR adds a rubocop check that forbids the use of url do blocks in homebrew/cask. It still allows them to be used in non-official taps. There's a little bit more discussion/context in the PR linked above, but basically these blocks require us to make network calls every time we generate the API data. It's very common for the API generation to fail because one of these URL blocks has an issue, and really the generation should be able to happen offline.

This will need to wait for Homebrew/homebrew-cask#186501 to be merged

CC: @Homebrew/cask

[MikeMcQuaid]

This is great, thanks @Rylan12!

As a follow-up: I do think it's worth odeprecateing this functionality. It's both pretty niche and very likely to start breaking in future if we're not using it ourselves in any official taps.

[MikeMcQuaid]

As a follow-up: I do think it's worth odeprecateing this functionality. It's both pretty niche and very likely to start breaking in future if we're not using it ourselves in any official taps.

To be explicit: this would ideally be a follow-up PR before we release Homebrew 4.4.0 but after this PR is merged.

[MikeMcQuaid]

As a follow-up: I do think it's worth odeprecateing this functionality. It's both pretty niche and very likely to start breaking in future if we're not using it ourselves in any official taps.

Opened #18407 to attempt this.

[Bo98]

As a follow-up: I do think it's worth odeprecateing this functionality. It's both pretty niche and very likely to start breaking in future if we're not using it ourselves in any official taps.

I agree with the point about it being untested. Though equally I don't want taps to be encouraged to start doing network requests on cask-load like I've seen way too many third-party formulae do. url do at least did things properly in that regard - just unsuitable for JSON API where we don't run Ruby.

I'm overall neutral, though if we do deprecate would suggest very clear messaging in what the replacement is.

[MikeMcQuaid]

Though equally I don't want taps to be encouraged to start doing network requests on cask-load like I've seen way too many third-party formulae do.

Those same taps will just end up complaining when we inevitably break this functionality because we don't use it ourselves. I'm not terribly worried about doing network requests on cask-load given this is not entirely dissimilar.

[MikeMcQuaid]

though if we do deprecate would suggest very clear messaging in what the replacement is.

Will happily take suggestions for what this messaging should be. As far as I can tell: there is no real replacement here.