Change command output instead

Library/Homebrew/cmd/outdated.rb

@@ -65,7 +65,9 @@ module Homebrew
             formulae: json_info(formulae),
             casks:    json_info(casks),
           }
-          puts JSON.pretty_generate(json)
+          # json v2.8.1 is inconsistent it how it renders empty arrays,
+          # so we use `[]` for consistency:
+          puts JSON.pretty_generate(json).gsub(/\[\n\n\s*\]/, "[]")
 
           outdated = formulae + casks
         else

Library/Homebrew/test/cmd/outdated_spec.rb

@@ -20,12 +20,9 @@ RSpec.describe Homebrew::Cmd::Outdated do
       }],
       casks:    [],
     })
-    # json v2.8.1 is inconsistent it how it renders empty arrays,
-    # for now we allow multiple outputs:
-    alternate_json = expected_json.gsub("[]", "[\n\n]")
 
     expect { brew "outdated", "--json=v2" }
-      .to output(match(/\A(#{Regexp.escape(expected_json)}|#{Regexp.escape(alternate_json)})\n\z/)).to_stdout
+      .to output("#{expected_json}\n").to_stdout
       .and be_a_success
   end
 end