feat: allow cask binaries on linux

Library/Homebrew/cask/artifact/symlinked.rb

@@ -62,7 +62,7 @@ module Cask
         end
 
         ohai "Linking #{self.class.english_name} '#{source.basename}' to '#{target}'"
-        create_filesystem_link(command:)
+        create_filesystem_link(command)
       end
 
       def unlink(command: nil, **)
@@ -72,14 +72,10 @@ module Cask
         Utils.gain_permissions_remove(target, command:)
       end
 
-      def create_filesystem_link(command: nil)
+      sig { params(command: T.class_of(SystemCommand)).void }
-        Utils.gain_permissions_mkpath(target.dirname, command:)
+      def create_filesystem_link(command); end
-
-        command.run! "/bin/ln", args: ["-h", "-f", "-s", "--", source, target],
-                                sudo: !target.dirname.writable?
-
-        add_altname_metadata(source, target.basename, command:)
-      end
     end
   end
 end
+
+require "extend/os/cask/artifact/symlinked"

Library/Homebrew/cask/dsl.rb

@@ -312,16 +312,17 @@ module Cask
     # ```ruby
     # sha256 arm:   "7bdb497080ffafdfd8cc94d8c62b004af1be9599e865e5555e456e2681e150ca",
     #        intel: "b3c1c2442480a0219b9e05cf91d03385858c20f04b764ec08a3fa83d1b27e7b2"
+    #        linux: "1a2aee7f1ddc999993d4d7d42a150c5e602bc17281678050b8ed79a0500cc90f"
     # ```
     #
     # @api public
-    def sha256(arg = nil, arm: nil, intel: nil)
+    def sha256(arg = nil, arm: nil, intel: nil, linux: nil)
       should_return = arg.nil? && arm.nil? && intel.nil?
 
       set_unique_stanza(:sha256, should_return) do
-        @on_system_blocks_exist = true if arm.present? || intel.present?
+        @on_system_blocks_exist = true if arm.present? || intel.present? || linux.present?
 
-        val = arg || on_arch_conditional(arm:, intel:)
+        val = arg || on_system_conditional(macos: on_arch_conditional(arm:, intel:), linux:)
         case val
         when :no_check
           val
@@ -352,6 +353,25 @@ module Cask
       end
     end
 
+    # Sets the cask's os strings.
+    #
+    # ### Example
+    #
+    # ```ruby
+    # os macos: "darwin", linux: "tux"
+    # ```
+    #
+    # @api public
+    def os(macos: nil, linux: nil)
+      should_return = macos.nil? && linux.nil?
+
+      set_unique_stanza(:os, should_return) do
+        @on_system_blocks_exist = true
+
+        on_system_conditional(macos:, linux:)
+      end
+    end
+
     # Declare dependencies and requirements for a cask.
     #
     # NOTE: Multiple dependencies can be specified.

Library/Homebrew/extend/on_system.rbi

@@ -20,4 +20,7 @@ module OnSystem::MacOSAndLinux
       .returns(T.type_parameter(:U))
   }
   def on_macos(&block); end
+
+  sig { params(arm: T.nilable(String), intel: T.nilable(String)).returns(T.nilable(String)) }
+  def on_arch_conditional(arm: nil, intel: nil); end
 end

Library/Homebrew/extend/os/cask/artifact/symlinked.rb

@@ -0,0 +1,5 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "extend/os/mac/cask/artifact/symlinked" if OS.mac?
+require "extend/os/linux/cask/artifact/symlinked" if OS.linux?

Library/Homebrew/extend/os/linux/cask/artifact/symlinked.rb

@@ -0,0 +1,26 @@
+# typed: strict
+# frozen_string_literal: true
+
+module OS
+  module Linux
+    module Cask
+      module Artifact
+        module Symlinked
+          extend T::Helpers
+
+          requires_ancestor { ::Cask::Artifact::Symlinked }
+
+          sig { params(command: T.class_of(SystemCommand)).void }
+          def create_filesystem_link(command)
+            ::Cask::Utils.gain_permissions_mkpath(target.dirname, command:)
+
+            command.run! "/bin/ln", args: ["--no-dereference", "--force", "--symbolic", source, target],
+                                    sudo: !target.dirname.writable?
+          end
+        end
+      end
+    end
+  end
+end
+
+Cask::Artifact::Symlinked.prepend(OS::Linux::Cask::Artifact::Symlinked)

Library/Homebrew/extend/os/linux/cask/installer.rb

@@ -15,6 +15,9 @@ module OS
         def check_stanza_os_requirements
           return if artifacts.all?(::Cask::Artifact::Font)
 
+          install_artifacts = artifacts.reject { |artifact| artifact.instance_of?(::Cask::Artifact::Zap) }
+          return if install_artifacts.all?(::Cask::Artifact::Binary)
+
           raise ::Cask::CaskError, "macOS is required for this software."
         end
       end

Library/Homebrew/extend/os/mac/cask/artifact/symlinked.rb

@@ -0,0 +1,30 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "cask/macos"
+
+module OS
+  module Mac
+    module Cask
+      module Artifact
+        module Symlinked
+          extend T::Helpers
+
+          requires_ancestor { ::Cask::Artifact::Symlinked }
+
+          sig { params(command: T.class_of(SystemCommand)).void }
+          def create_filesystem_link(command)
+            ::Cask::Utils.gain_permissions_mkpath(target.dirname, command:)
+
+            command.run! "/bin/ln", args: ["-h", "-f", "-s", "--", source, target],
+                                    sudo: !target.dirname.writable?
+
+            add_altname_metadata(source, target.basename, command:)
+          end
+        end
+      end
+    end
+  end
+end
+
+Cask::Artifact::Symlinked.prepend(OS::Mac::Cask::Artifact::Symlinked)