livecheck migration: create Homebrew::Livecheck

[nandahkrishna]

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This PR adds the Homebrew::Livecheck module containing livecheck's core logic. PR #8180 was hard to review as it was too large, so it was split up, with the original PR being exclusively to migrate the command.

Changes/suggestions yet to handle:

• I'm working on the tests and am nearly done with them, I'll push them soon.

This PR will have to be merged before we can merge #8180.

[nandahkrishna]

With the latest push, some tests have been added. They are a work in progress (style will fail as well) and I was wondering whether using a double as a substitute for a Formula was okay.

We have a lot of Formula method calls in livecheck, and as a result I've got a little too many allows, and some for method chaining as well. The alternative I'm considering is using :integration_test so that I can setup a test formula (just as in the dev-cmd PR's test). What do you think @MikeMcQuaid?

[MikeMcQuaid]

Will have more comments to add on this but should give you enough to work on and looks good so far!

[MikeMcQuaid]

A few more comments based on "finishing this off". A few of these are general so please check if there's places I've missed where the same comment may apply. Thanks, great work so far @nandahkrishna!

[nandahkrishna]

An update:
Most changes have been completed, it's just the tests and trying to combine code from audit or notability left. Should be pushing them soon.

[nandahkrishna]

With the latest push, most changes have been addressed. Some points to note:

• This PR depends on livecheck migration: add strategies #8255 and the final livecheck_formulae test will be added after that PR is merged.
• Would we require more tests for other methods or would that be too much?
• I don't think we can do away with the GITHUB_SPECIAL_CASES, so if there's anything we have to do to ensure the formulae in that list still exist, I'll create a PR for that (maybe along with the RuboCops and audits).

Looking forward to your reviews @samford and @MikeMcQuaid!

[MikeMcQuaid]

A few nits but looking good to me. I'm happy to merge this when you're happy with the state of my questions.

[nandahkrishna]

With the latest push the following changes have been made:

• Some documentation that definitely needs to be improved.
• Tests for preprocess_url and livecheck_formulae (both of which needed one unfrozen Formula URL String).
• Changed the usage of formula.stable? to formula.head? in most cases.

Will make further changes based on your reviews @MikeMcQuaid @samford. Thanks!

[MikeMcQuaid]

Looks good! Nothing here blocking this from my perspective. 👍🏻 to merge when @samford is.

[samford]

I'm busy with work at the moment but I'm planning to take a pass at this in the evening (around 5 or 6 hours from now).

If this can't wait until then, I imagine it's probably in good enough shape that any issues are likely minor and I could address them in a follow-up PR, if necessary. Otherwise, if this can wait, I'll get to it as soon as I can.

[samford]

I've left a few comments but they're mostly straightforward suggestions. The message.presence issue may require a little discussion but it's something that I would like to sort out before this is merged (as it modifies existing behavior).

Once these latest review items are resolved, I'm good with this PR being merged. The documentation comments could use a little work but I don't want to hold this up, so I'll take care of it in a later PR.

It's very late over here and I'm calling it a night but I'll check back in the morning.

[nandahkrishna]

Well, I'm not sure I understand why this (SSL error) is happening with the tests. They all pass locally, and the only difference now compared to a previous CI run that was 🟢, is that I'm now setting the debug? value to true in an attempt to increase coverage. I'll take a look at this in more detail but do let me know if there's something I'm doing wrong.

[samford]

The debug output still contains the normal (non-debug) output at the end, so I would think it should still be fine. The test works fine locally, so it must just be that the SSL error prevents livecheck from identifying a version and that in turn results in the expected output not being present. I have no idea why we keep getting an SSL error for any related tests checking GitHub, though.

I would be interested to see what happens on CI if we check a non-GitHub URL in the livecheck_formulae test. Just as a quick example, we could check some formulae.brew.sh JSON data:

let(:f) do
  formula("test") do
    desc "Test formula"
    homepage "https://brew.sh"
    url "https://brew.sh/test-0.0.1.tgz"
    head "https://github.com/Homebrew/brew.git"

    livecheck do
      url "https://formulae.brew.sh/api/formula/readline.json"
      regex(/"stable":"(\d+(?:\.\d+)+)"/i)
    end
  end
end

It may be that there's something better to check but this would at least let us know if this is only related to GitHub URLs or if it affects other HTTPS URLs.

You would also need to add the previous GitHub URL (https://github.s3.amazonaws.com/Homebrew/brew/releases/latest) as a separate variable and update the preprocess_url test to use that, otherwise that test will be unhappy.

Worst case scenario, it may be that we have to drop the livecheck_formulae test for now and address it sometime after GSoC with the other network-related tests (like we did with the PageMatch#find_versions test in the strategies PR).

[nandahkrishna]

That seems to have worked! Thank you Sam.

Maybe we should, for whatever reason, avoid GitHub URLs and stick with a brew.sh URL for the network-related tests.

[samford]

Hm, I do wonder what the issue is with the GitHub URL. We didn't have any problems checking GitHub URLs on homebrew-livecheck CI, other than rate limiting. The tag_info test in the Git strategy also checks a GitHub URL and that seemed to work, so it's a bit baffling.

Since this works with a formulae.brew.sh URL, I suppose the question is whether we want to move forward with this or to simply drop the livecheck_formulae test in favor of working on it later with the other network-related tests. I'm fine either way, so I'll leave it up to @MikeMcQuaid.

If we end up moving forward with the formulae.brew.sh check, is there any formula that we can pretty much rely on never being deleted in the future? I simply picked readline because it's the most popular non-versioned formula.

Requested changes have been addressed

[nandahkrishna]

I picked ruby because pretty much everything in Homebrew is done with Ruby, and though we use the system Ruby I couldn't see a future where we would remove the ruby formula. Of course, if there's a better alternative I'm okay with changing it.

[samford]

One little change and then I think that's all for me, outside of resolving the open question above.

[MikeMcQuaid]

Great work, thanks again @nandahkrishna!