Refactor: make persister easier to reason about.

Before `statuses_from_previous_runs` depended upon the
`@previous_runs` ivar, which was set by `persist`, so
the method would fail if called before `persist`, and
if called after `persist` was done, it would re-use the
old `@previous_runs` state.  Pretty weird.

Far better to pass explicit local variables around.

Author: myronmarston

lib/rspec/core/example_status_persister.rb

@@ -27,24 +27,22 @@ def persist
           # condition where parallel or unrelated spec runs race to
           # update the same file
           f.flock(File::LOCK_EX)
-          @previous_runs = f.read
+          unparsed_previous_runs = f.read
           f.rewind
-          f.write(dumped_statuses)
+          f.write(dump_statuses(unparsed_previous_runs))
           f.flush
           f.truncate(f.pos)
         end
       end
 
     private
 
-      def dumped_statuses
+      def dump_statuses(unparsed_previous_runs)
+        statuses_from_previous_runs = ExampleStatusParser.parse(unparsed_previous_runs)
+        merged_statuses = ExampleStatusMerger.merge(statuses_from_this_run, statuses_from_previous_runs)
         ExampleStatusDumper.dump(merged_statuses)
       end
 
-      def merged_statuses
-        ExampleStatusMerger.merge(statuses_from_this_run, statuses_from_previous_runs)
-      end
-
       def statuses_from_this_run
         @examples.map do |ex|
           result = ex.execution_result
@@ -56,10 +54,6 @@ def statuses_from_this_run
           }
         end
       end
-
-      def statuses_from_previous_runs
-        ExampleStatusParser.parse(@previous_runs)
-      end
     end
 
     # Merges together a list of example statuses from this run

spec/rspec/core/example_status_persister_spec.rb

@@ -73,7 +73,7 @@ def new_example(id, metadata = {})
 
         # dumped_statuses is called after the file is locked but
         # before the output is written
-        allow(persister_1).to receive(:dumped_statuses).and_wrap_original do |m, *args|
+        allow(persister_1).to receive(:dump_statuses).and_wrap_original do |m, *args|
           persister_2_thread = Thread.new { persister_2.persist }
           m.call(*args)
         end