fix: add blank lines to empty hashs - json 2.8.x regression

lib/pact/matchers/unix_diff_formatter.rb

@@ -62,6 +62,8 @@ def generate_string diff, target
         begin
           # Can't think of an elegant way to check if we can pretty generate other than to try it and maybe fail
           json = fix_blank_lines_in_empty_hashes JSON.pretty_generate(comparable)
+          json = add_blank_lines_in_empty_hashes json
+          json = add_blank_lines_in_empty_arrays json
           add_comma_to_end_of_arrays json
         rescue JSON::GeneratorError
           comparable.to_s

lib/pact/shared/jruby_support.rb

@@ -14,5 +14,14 @@ def fix_blank_lines_in_empty_hashes json
       json.gsub(/({\n)\n(\s*})/,'\1\2')
     end
 
+    # preserve pre json 2.8.x behaviour
+    # https://github.com/ruby/json/pull/626
+    def add_blank_lines_in_empty_hashes(json)
+      json.gsub(/({\s*})/, "{\n  }")
+    end
+
+    def add_blank_lines_in_empty_arrays(json)
+      json.gsub(/\[\s*\]/, "[\n  ]")
+    end
   end
 end

spec/lib/pact/matchers/unix_diff_formatter_spec.rb

@@ -123,6 +123,7 @@ module Matchers
           end
 
           it "generates the right number of lines, even with ActiveSupport loaded" do
+            puts subject
             expect(line_count).to eq 7 + key_lines_count
           end
         end