feat: print a new line between JSON documents when using --format json

This allows the stream to be parsed as jsonl

Fixes: pact-foundation/pact-go#88

lib/pact/provider_verifier/app.rb

@@ -40,6 +40,7 @@ def call
       def setup
         print_deprecation_note
         set_environment_variables
+        require_rspec_monkeypatch_for_jsonl
         require_pact_project_pact_helper # Beth: not sure if this is needed, hangover from pact-provider-proxy?
       end
 
@@ -127,6 +128,12 @@ def require_pact_project_pact_helper
         require ENV['PACT_PROJECT_PACT_HELPER'] if ENV.fetch('PACT_PROJECT_PACT_HELPER','') != ''
       end
 
+      def require_rspec_monkeypatch_for_jsonl
+        if options.format == 'json'
+          require 'pact/provider_verifier/rspec_json_formatter_monkeypatch'
+        end
+      end
+
       def custom_provider_headers_for_env_var
         if options.custom_provider_header && options.custom_provider_header.any?
           options.custom_provider_header.join("\n")

lib/pact/provider_verifier/rspec_json_formatter_monkeypatch.rb

@@ -0,0 +1,34 @@
+require 'rspec'
+
+begin
+  require 'rspec/core/formatters/json_formatter'
+
+  RSpec::Core::Formatters::JsonFormatter
+
+  # This looks dodgy, but it's actually safer than inheriting from
+  # RSpec::Core::Formatters::JsonFormatter and using a custom class,
+  # because if the JsonFormatter class gets refactored,
+  # the --format json option will still work, but the inheritance will break.
+
+  module RSpec
+    module Core
+      module Formatters
+        class JsonFormatter
+          alias_method :old_close, :close
+
+          def close(*args)
+            # Append a new line so that the output stream can be split at
+            # the new lines, and each JSON document parsed separately
+            old_close(*args)
+            output.write("\n")
+          end
+        end
+      end
+    end
+  end
+
+rescue NameError
+  Pact.configuration.error_stream.puts "WARN: Could not find RSpec::Core::Formatters::JsonFormatter to modify it to put a new line between JSON result documents."
+rescue LoadError
+  Pact.configuration.error_stream.puts "WARN: Could not load rspec/core/formatters/json_formatter to modify it to put a new line between JSON result documents."
+end

spec/integration_spec.rb

@@ -51,14 +51,14 @@
     subject { `bundle exec bin/pact-provider-verifier ./test/me-they.json ./test/me-they.json --format json -a 1.0.100 --provider-base-url http://localhost:4567 --provider-states-setup-url http://localhost:4567/provider-state` }
 
     it "sends the results of both pacts to stdout" do
-      expect(subject).to include "}{"
+      expect(subject).to include "}\n{"
       expect(subject.scan(/\d examples, \d failure/).count).to eq 2
     end
 
     it "allows the results to be split and parsed to JSON" do
-      result_1, result_2 = subject.split("}{", 2)
-      JSON.parse(result_1 + "}")
-      JSON.parse("{" + result_2)
+      result_1, result_2 = subject.split("\n", 2)
+      JSON.parse(result_1)
+      JSON.parse(result_2)
     end
   end