cask: extract refresh_for_tag to tolerate asymmetric variations

Add `Cask::Cask#refresh_for_tag`, which refreshes a cask for a simulated
OS/arch tag and tolerates casks that intentionally omit some platforms
(e.g. an `on_linux` block defining only `x86_64_linux`). Use it from
`to_hash_with_variations`, `bump-cask-pr` and `generate-cask-ci-matrix`
instead of repeating the rescue in each caller.

Previously `to_hash_with_variations` raised `invalid 'sha256' value: nil`
for such casks, aborting variation generation entirely.

Signed-off-by: Patrick Linnane <patrick@linnane.io>

Author: p-linnane

Library/Homebrew/cask/cask.rb

@@ -163,6 +163,24 @@ def refresh
       raise CaskInvalidError.new(token, e.message), e.backtrace
     end
 
+    # Refresh the cask as evaluated on `tag` and yield. Returns `nil` instead of
+    # raising when the cask has `on_system` blocks that omit the tag.
+    sig {
+      type_parameters(:U)
+        .params(tag: ::Utils::Bottles::Tag, _block: T.proc.returns(T.type_parameter(:U)))
+        .returns(T.nilable(T.type_parameter(:U)))
+    }
+    def refresh_for_tag(tag, &_block)
+      Homebrew::SimulateSystem.with(os: tag.system, arch: tag.arch) do
+        refresh
+        yield
+      end
+    rescue CaskInvalidError, CaskUnreadableError
+      raise unless on_system_blocks_exist?
+
+      nil
+    end
+
     def_delegators :@dsl, *::Cask::DSL::DSL_METHODS
 
     sig { returns(DSL::Caveats) }
@@ -592,9 +610,7 @@ def to_hash_with_variations
                     !dsl!.depends_on_set_in_block? &&
                     macos_requirements.any? { |requirement| !requirement.allows?(bottle_tag.to_macos_version) }
 
-            Homebrew::SimulateSystem.with_tag(bottle_tag) do
-              refresh
-
+            refresh_for_tag(bottle_tag) do
               to_h.each do |key, value|
                 next if HASH_KEYS_TO_SKIP.include? key
                 next if value.to_s == hash[key].to_s

Library/Homebrew/dev-cmd/bump-cask-pr.rb

@@ -293,17 +293,11 @@ def replace_version_and_checksum(cask, new_hash, new_version, contents)
         cask_sourcefile_path = cask.sourcefile_path
         raise "unexpected nil cask.sourcefile_path" unless cask_sourcefile_path
 
+        old_cask = Cask::CaskLoader.load(cask_sourcefile_path)
         generate_system_options(cask, new_version).each do |os, arch|
-          SimulateSystem.with(os:, arch:) do
-            # Handle the cask being invalid for specific os/arch combinations
-            old_cask = begin
-              Cask::CaskLoader.load(cask_sourcefile_path)
-            rescue Cask::CaskInvalidError, Cask::CaskUnreadableError
-              raise unless cask.on_system_blocks_exist?
-            end
-            next if old_cask.nil?
-
-            # Skip archs excluded by the reloaded cask's `depends_on arch:`.
+          tag = Utils::Bottles::Tag.new(system: os, arch:)
+          old_cask.refresh_for_tag(tag) do
+            # Skip archs excluded by the cask's `depends_on arch:`.
             reloaded_archs = old_cask.depends_on.arch&.filter_map { |a| a[:type] }&.uniq
             next if reloaded_archs.present? && reloaded_archs.exclude?(arch)
 

Library/Homebrew/dev-cmd/generate-cask-ci-matrix.rb

@@ -188,19 +188,15 @@ def runner_arch_pairs(runners:, multi_os:)
       def architectures(cask:, os:)
         architectures = T.let([], T::Array[Symbol])
         [:arm, :intel].each do |arch|
-          tag = Utils::Bottles::Tag.new(system: os, arch: arch)
-          Homebrew::SimulateSystem.with_tag(tag) do
-            cask.refresh
-
+          tag = Utils::Bottles::Tag.new(system: os, arch:)
+          cask.refresh_for_tag(tag) do
             if cask.depends_on.arch.blank?
               architectures = RUNNERS.keys.map { |r| r.fetch(:arch).to_sym }.uniq.sort
               next
             end
 
             architectures = cask.depends_on.arch.map { |arch| arch[:type] }
           end
-        rescue ::Cask::CaskInvalidError
-          # Can't read cask for this system-arch combination.
         end
 
         architectures

Library/Homebrew/test/cask/cask_spec.rb

@@ -596,6 +596,20 @@ def write_auto_updates_cask(path, version:, artifacts:, token: "auto-updates-bun
     end
   end
 
+  describe "#refresh_for_tag" do
+    let(:cask) { Cask::CaskLoader.load("on-linux-asymmetric") }
+
+    it "yields with the cask refreshed for a supported tag" do
+      tag = Utils::Bottles::Tag.new(system: :sonoma, arch: :intel)
+      expect(cask.refresh_for_tag(tag) { cask.url.to_s }).to include("caffeine-intel-darwin")
+    end
+
+    it "returns nil for a tag the cask does not support" do
+      tag = Utils::Bottles::Tag.new(system: :linux, arch: :arm)
+      expect(cask.refresh_for_tag(tag) { cask.url }).to be_nil
+    end
+  end
+
   describe "#to_hash_with_variations" do
     let!(:original_macos_version) { MacOS.full_version.to_s }
     let(:expected_versions_variations) do
@@ -744,6 +758,14 @@ def write_auto_updates_cask(path, version:, artifacts:, token: "auto-updates-bun
       expect(JSON.pretty_generate(h["variations"])).to eq expected_sha256_variations_os.strip
     end
 
+    it "omits tags a cask intentionally doesn't define in on_system blocks" do
+      c = Cask::CaskLoader.load("on-linux-asymmetric")
+      h = c.to_hash_with_variations
+
+      expect(h["variations"]).to include(:x86_64_linux)
+      expect(h["variations"]).not_to include(:arm64_linux)
+    end
+
     # NOTE: The calls to `Cask.generating_hash!` and `Cask.generated_hash!`
     #       are not idempotent so they can only be used in one test.
     it "returns the correct hash placeholders" do

Library/Homebrew/test/support/fixtures/cask/Casks/on-linux-asymmetric.rb

@@ -0,0 +1,24 @@
+# typed: false
+
+cask "on-linux-asymmetric" do
+  arch arm: "arm", intel: "intel"
+  os macos: "darwin", linux: "linux"
+
+  version "1.2.3"
+
+  url "file://#{TEST_FIXTURE_DIR}/cask/caffeine-#{arch}-#{os}.zip"
+  homepage "https://brew.sh/"
+
+  on_macos do
+    sha256 arm:   "67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94",
+           intel: "8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b"
+  end
+
+  on_linux do
+    sha256 x86_64_linux: "8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b"
+
+    depends_on arch: :x86_64
+  end
+
+  app "Caffeine.app"
+end