generate-cask-ci-matrix: respect on_linux architecture constraints

Author: biplavbarua

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

@@ -175,8 +175,12 @@ def architectures(cask:, os: :macos, arch: :arm)
             cask.refresh
 
             if cask.depends_on.arch.blank?
-              architectures = if cask.artifacts.any?(Cask::Artifact::AppImage)
-                [:intel]
+              # If the Cask does not define a general architecture requirement,
+              # check if there is one specific to Linux.
+              architectures = if (linux_archs = Homebrew::SimulateSystem.with(os: :linux) do
+                Cask::CaskLoader.load(cask.sourcefile_path).depends_on.arch
+              end)
+                linux_archs.map { |a| a[:type] }.uniq.sort
               else
                 RUNNERS.keys.map { |r| r.fetch(:arch).to_sym }.uniq.sort
               end

Library/Homebrew/test/dev-cmd/generate-cask-ci-matrix_spec.rb

@@ -9,11 +9,11 @@
 
   describe "#architectures" do
     let(:cmd) { described_class.new }
-    let(:appimage_cask) { Cask::CaskLoader.load(TEST_FIXTURE_DIR/"cask/Casks/with-appimage.rb") }
+    let(:linux_arch_cask) { Cask::CaskLoader.load(TEST_FIXTURE_DIR/"cask/Casks/on-linux-arch.rb") }
     let(:standard_cask) { Cask::CaskLoader.load(TEST_FIXTURE_DIR/"cask/Casks/basic-cask.rb") }
 
-    it "returns only [:intel] for Casks with an AppImage" do
-      expect(cmd.architectures(cask: appimage_cask)).to eq([:intel])
+    it "returns only [:intel] for Casks with an on_linux arch dependency" do
+      expect(cmd.architectures(cask: linux_arch_cask)).to eq([:intel])
     end
 
     it "returns all runners for standard Casks" do

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

@@ -0,0 +1,15 @@
+cask "on-linux-arch" do
+  version "1.0.0"
+  sha256 :no_check
+
+  url "https://brew.sh/"
+  name "On Linux Arch"
+  desc "Cask with on_linux architecture dependency"
+  homepage "https://brew.sh/"
+
+  on_linux do
+    depends_on arch: :intel
+  end
+
+  app "On Linux Arch.app"
+end