Allow diffs to be created from overlapping hunks

[fix #228][fix #225]

config/reek.yml

@@ -29,6 +29,7 @@ FeatureEnvy:
   # Nature of OptionParser :(
   - Mutant::CLI#add_environment_options
   - Mutant::Env#scope_name
+  - Mutant::Diff#minimized_hunks
   - Mutant::Integration::Rspec#run
   - Mutant::Integration::Rspec::Rspec2#full_description
   - Mutant::Integration::Rspec::Rspec3#full_description

lib/mutant/diff.rb

@@ -18,9 +18,11 @@ module Mutant
     # @api private
     #
     def diff
-      return unless diffs.length.equal?(1)
-      ::Diff::LCS::Hunk.new(old, new, diffs.first, max_length, 0)
-        .diff(:unified) << NEWLINE
+      return if diffs.length.equal?(0)
+
+      minimized_hunks.map do |hunk|
+        hunk.diff(:unified) << NEWLINE
+      end.join
     end
     memoize :diff
 
@@ -77,7 +79,41 @@ module Mutant
     def diffs
       ::Diff::LCS.diff(old, new)
     end
-    memoize :diffs
+
+    # Return hunks
+    #
+    # @return [Array<Diff::LCS::Hunk>]
+    #
+    # @api private
+    #
+    def hunks
+      diffs.map do |diff|
+        ::Diff::LCS::Hunk.new(old, new, diff, max_length, 0)
+      end
+    end
+
+    # Return minimized hunks
+    #
+    # @return [Array<Diff::LCS::Hunk>]
+    #
+    # @api pirvate
+    #
+    # rubocop gets that one wrong. hunks = hunks() iS NOT equivalent to hunks = hunks, unparser does this right ;)
+    #
+    # rubocop:disable MethodCallParentheses
+    #
+    def minimized_hunks
+      hunks = hunks()
+
+      hunks.drop(1).each_with_object([hunks.first]) do |right, aggregate|
+        left = aggregate.last
+        if right.overlaps?(left)
+          right.merge(left)
+          aggregate.pop
+        end
+        aggregate << right
+      end
+    end
 
     # Return max length
     #

lib/mutant/mutator/node/send.rb

@@ -27,7 +27,7 @@ module Mutant
           :>= =>         [:>, :==, :eql?, :equal?],
           :<= =>         [:<, :==, :eql?, :equal?],
           :> =>          [:==, :eql?, :equal?],
-          :< =>          [:==, :eql?, :equal?],
+          :< =>          [:==, :eql?, :equal?]
         )
 
       private

spec/unit/mutant/diff_spec.rb

@@ -41,6 +41,26 @@ RSpec.describe Mutant::Diff do
 
     subject { object.diff }
 
+    context 'when there is a diff at begin and end' do
+      let(:old) { %w[foo bar foo] }
+      let(:new) { %w[baz bar baz] }
+
+      let(:expectation) do
+        strip_indent(<<-STR)
+          @@ -1,4 +1,4 @@
+          -foo
+          +baz
+           bar
+          -foo
+          +baz
+        STR
+      end
+
+      it { should eql(expectation) }
+
+      it_should_behave_like 'an idempotent method'
+    end
+
     context 'when there is a diff at begin of hunk' do
       let(:old) { %w[foo bar] }
       let(:new) { %w[baz bar] }

spec/unit/mutant/reporter/cli_spec.rb

@@ -140,9 +140,7 @@ RSpec.describe Mutant::Reporter::CLI do
     subject { described_class.build(output) }
 
     let(:progressive_format) do
-      described_class::Format::Progressive.new(
-        tty: tty?,
-      )
+      described_class::Format::Progressive.new(tty: tty?)
     end
 
     let(:framed_format) do