cask: extract refresh_for_tag to tolerate asymmetric variations

[p-linnane]

Cask#to_hash_with_variations iterates OnSystem::VALID_OS_ARCH_TAGS and refreshes the cask for each tag, but with no rescue. When a cask uses on_system blocks that legitimately omit some platforms — e.g.

on_linux do
  sha256 x86_64_linux: "..."
  depends_on arch: :x86_64
end

— the (linux, arm) iteration raised CaskInvalidError: invalid 'sha256' value: nil and aborted variation generation entirely. This broke generate-cask-ci-matrix on homebrew-cask PRs submitting such casks (e.g. Homebrew/homebrew-cask#266359).

Per review feedback, rather than repeating the rescue in each caller, this extracts a shared Cask::Cask#refresh_for_tag(tag, &block) helper that refreshes the cask for a simulated OS/arch tag and returns nil (instead of raising) when the cask intentionally omits that tag. It re-raises for casks without on_system blocks, since those failures aren't platform-specific.

All three existing callers of the pattern now use it:

• Cask#to_hash_with_variations
• dev-cmd/bump-cask-pr (loads the source cask once, then refreshes per tag)
• dev-cmd/generate-cask-ci-matrix

The helper uses SimulateSystem.with (not with_tag) so it tolerates the invalid OS/arch combinations bump-cask-pr can generate on older macOS hosts, matching the previous behaviour.

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• AI was used to generate or assist with generating this PR.

AI (Claude Code) assisted with the implementation and this description. Added a fixture cask (on-linux-asymmetric) plus specs for #refresh_for_tag (supported tag yields; unsupported tag returns nil) and #to_hash_with_variations (omits the unsupported tag). Verified with brew lgtm and the cask, bump-cask-pr and generate-cask-ci-matrix specs.

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[Copilot]

Pull request overview

This PR updates Cask::Cask#to_hash_with_variations to tolerate casks that intentionally define only a subset of OS/arch combinations inside on_system blocks, by rescuing per-tag CaskInvalidError/CaskUnreadableError during simulated tag refresh and skipping unsupported combinations instead of aborting the whole variations computation.

Changes:

• Wrap the per-OnSystem::VALID_OS_ARCH_TAGS SimulateSystem.with_tag + refresh + to_h comparison in a begin/rescue.
• Skip tags that raise CaskInvalidError or CaskUnreadableError during per-tag refresh, allowing supported tags to still be collected into the variations hash.

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[MikeMcQuaid]

Thanks, code looks good!

Mirrors the existing rescue patterns in bump-cask-pr.rb and generate-cask-ci-matrix.rb.

Given it's 3 cases: I think this would ideally instead provide a shared API that can be used by all 3 callers (and look for other potential callers) so we don't have to keep adding this in new places over time.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

[MikeMcQuaid]

Looks great, thanks!