Refactor ConflictsWith to be a DelegateClass(Hash).

Library/Homebrew/cask/cask.rb

@@ -133,7 +133,7 @@ def to_h
         end,
         "caveats"        => caveats,
         "depends_on"     => depends_on,
-        "conflicts_with" => conflicts_with.to_h,
+        "conflicts_with" => conflicts_with,
         "container"      => container,
         "auto_updates"   => auto_updates,
       }

Library/Homebrew/cask/dsl/conflicts_with.rb

@@ -1,33 +1,28 @@
+require "extend/hash_validator"
+using HashValidator
+
 module Cask
   class DSL
-    class ConflictsWith
-      VALID_KEYS = Set.new [
+    class ConflictsWith < DelegateClass(Hash)
+      VALID_KEYS = [
         :formula,
         :cask,
         :macos,
         :arch,
         :x11,
         :java,
-      ]
-
-      attr_reader *VALID_KEYS
-
-      def initialize(pairs = {})
-        @pairs = pairs
+      ].freeze
 
-        VALID_KEYS.each do |key|
-          instance_variable_set("@#{key}", Set.new)
-        end
+      def initialize(**pairs)
+        pairs.assert_valid_keys!(*VALID_KEYS)
 
-        pairs.each do |key, value|
-          raise "invalid conflicts_with key: '#{key.inspect}'" unless VALID_KEYS.include?(key)
+        super(Hash[pairs.map { |k, v| [k, Set.new([*v])] }])
 
-          instance_variable_set("@#{key}", instance_variable_get("@#{key}").merge([*value]))
-        end
+        self.default = Set.new
       end
 
-      def to_h
-        Hash[VALID_KEYS.map { |key| [key, instance_variable_get("@#{key}").to_a] }]
+      def to_json(generator)
+        Hash[map { |k, v| [k, v.to_a] }].to_json(generator)
       end
     end
   end

Library/Homebrew/cask/installer.rb

@@ -104,7 +104,7 @@ def install
     def check_conflicts
       return unless @cask.conflicts_with
 
-      @cask.conflicts_with.cask.each do |conflicting_cask|
+      @cask.conflicts_with[:cask].each do |conflicting_cask|
         begin
           conflicting_cask = CaskLoader.load(conflicting_cask)
           if conflicting_cask.installed?

Library/Homebrew/test/cask/dsl_spec.rb

@@ -401,7 +401,7 @@ def caveats
       let(:token) { "with-conflicts-with" }
 
       it "allows conflicts_with stanza to be specified" do
-        expect(cask.conflicts_with.formula).not_to be nil
+        expect(cask.conflicts_with[:formula]).to be_empty
       end
     end