cask/audit: allow the homepage https audit to have exceptions

[Rylan12]

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This PR adds a cert_error_allowlist audit exception for the audit that checks HTTPS availability for cask homepages.

This list is designed to be used to allow audits to pass for the formulae affected by the Cloudflare issue we've been having.

CC: @bevanjkay and @GregBrimble

Corresponding homebrew/cask PR: Homebrew/homebrew-cask#112093 (can be merged in either order)

[BrewTestBot]

Review period will end on 2021-10-05 at 23:30:17 UTC.

[Rylan12]

The latest commit also refactors the tap_audit_exception methods that existed as (essentially) duplicates in formula_auditor.rb, utils/shared_audits.rb, and cask/audit.rb into a single method Tap#audit_exception. This required some other minor refactoring. I've tested almost all the lists and believe everything is still working as expected.

[MikeMcQuaid]

This PR adds a cert_error_allowlist audit exception for the audit that checks HTTPS availability for cask homepages.

This list is designed to be used to allow audits to pass for the formulae affected by the Cloudflare issue we've been having.

Code looks good to me! Might just want to name it something like homepage_audit_skiplist or something to make clearer what the code is doing (rather than the intent).

[BrewTestBot]

Review period ended.

[Rylan12]

Thanks, good feedback. I haven't had free time to implement this yet and might not until the weekend, so apologies for the delay.

[Rylan12]

Okay, I looked at this again but wasn't able to get the tests to work. The problem is that I've moved the logic that handles the exceptions to a Tap instance method to avoid needing to duplicate the method in Formula and Cask (and a third place that I'm blanking on). This makes the exception handling unreachable when {formula,cask}.tap is nil which makes sense. However, when the tests are run (primarily the dev-cmd/audit_spec.rb tests for FormulaAuditor) the generated formulae do not have a tap associated with them, so the exception list is never reached.

I tried a handful of things to trick the tests into thinking it has a tap so as not to mass-change a ton of tests but I think the solution is to change the logic to ensure that even these formulae have a tap associated (maybe test/tap or something like that to avoid weirdness with a CoreTap). I only briefly looked into this so I'll hopefully spend more time later fixing that up.

I'm on break this week (after Tuesday) so hopefully, I'll have some more time. I've found that I consistently have a lot less free time during the week than I expect so progress here has been a bit slow.

[MikeMcQuaid]

I think this is fine without adding tests FWIW

[Rylan12]

I think this is fine without adding tests FWIW

The problem is that it breaks existing tests (but because the tests no longer set the formula being tested up correctly rather than because this PR breaks functionality)

[MikeMcQuaid]

Ah gotcha 😭

[Rylan12]

Got the tests working!

For all of the formula_auditor tests, I've stubbed Formula#tap to return a test tap (test/tap) that contains the necessary exceptions.