Change when max_diff_size is applied

- This appears to satisfy the issues found in #60 as well as providing the
  additional fixes required to properly test ldiff.

Resolves #60

History.md

@@ -1,5 +1,16 @@
 # History
 
+## 1.4.2 / 2020-06-23
+
+- Camille Drapier fixed a small issue with RuboCop configuration. [#59][]
+- Applied another fix (and unit test) to fix an issue for the Chef team.
+  [#60][], [#61][]
+
+## 1.4.1 / 2020-06-23
+
+- Fix an issue where diff sizes could be negative, and they should be. [#57][],
+  [#58][]
+
 ## 1.4 / 2020-06-23
 
 - Ruby versions lower than 2.4 are soft-deprecated and will not be run as
@@ -245,3 +256,8 @@
 [#49]: https://github.com/halostatue/diff-lcs/pull/49
 [#52]: https://github.com/halostatue/diff-lcs/pull/52
 [#53]: https://github.com/halostatue/diff-lcs/issues/53
+[#57]: https://github.com/halostatue/diff-lcs/issues/57
+[#58]: https://github.com/halostatue/diff-lcs/pull/58
+[#59]: https://github.com/halostatue/diff-lcs/pull/59
+[#60]: https://github.com/halostatue/diff-lcs/issues/60
+[#61]: https://github.com/halostatue/diff-lcs/pull/61

diff-lcs.gemspec

@@ -1,15 +1,15 @@
 # -*- encoding: utf-8 -*-
-# stub: diff-lcs 1.4.1 ruby lib
+# stub: diff-lcs 1.4.2 ruby lib
 
 Gem::Specification.new do |s|
   s.name = "diff-lcs".freeze
-  s.version = "1.4.1"
+  s.version = "1.4.2"
 
   s.required_rubygems_version = Gem::Requirement.new(">= 0".freeze) if s.respond_to? :required_rubygems_version=
   s.metadata = { "bug_tracker_uri" => "https://github.com/halostatue/diff-lcs/issues", "homepage_uri" => "https://github.com/halostatue/diff-lcs", "source_code_uri" => "https://github.com/halostatue/diff-lcs" } if s.respond_to? :metadata=
   s.require_paths = ["lib".freeze]
   s.authors = ["Austin Ziegler".freeze]
-  s.date = "2020-06-23"
+  s.date = "2020-06-24"
   s.description = "Diff::LCS computes the difference between two Enumerable sequences using the\nMcIlroy-Hunt longest common subsequence (LCS) algorithm. It includes utilities\nto create a simple HTML diff output format and a standard diff-like tool.\n\nThis is release 1.4, providing a simple extension that allows for\nDiff::LCS::Change objects to be treated implicitly as arrays. Ruby versions\nbelow 2.5 are soft-deprecated.\n\nThis means that older versions are no longer part of the CI test suite. If any\nchanges have been introduced that break those versions, bug reports and patches\nwill be accepted, but it will be up to the reporter to verify any fixes prior\nto release. A future release will completely break compatibility.".freeze
   s.email = ["halostatue@gmail.com".freeze]
   s.executables = ["htmldiff".freeze, "ldiff".freeze]

lib/diff/lcs.rb

@@ -49,7 +49,7 @@ module Diff; end unless defined? Diff # rubocop:disable Style/Documentation
 #          a x b y c z p d q
 #    a b c a x b y c z
 module Diff::LCS
-  VERSION = '1.4.1'
+  VERSION = '1.4.2'
 end
 
 require 'diff/lcs/callbacks'

lib/diff/lcs/hunk.rb

@@ -2,12 +2,12 @@
 
 require 'diff/lcs/block'
 
-# A Hunk is a group of Blocks which overlap because of the context
-# surrounding each block. (So if we're not using context, every hunk will
-# contain one block.) Used in the diff program (bin/diff).
+# A Hunk is a group of Blocks which overlap because of the context surrounding
+# each block. (So if we're not using context, every hunk will contain one
+# block.) Used in the diff program (bin/ldiff).
 class Diff::LCS::Hunk
-  # Create a hunk using references to both the old and new data, as well as
-  # the piece of data.
+  # Create a hunk using references to both the old and new data, as well as the
+  # piece of data.
   def initialize(data_old, data_new, piece, flag_context, file_length_difference)
     # At first, a hunk will have just one Block in it
     @blocks = [Diff::LCS::Block.new(piece)]
@@ -61,17 +61,20 @@ def flag_context=(context) #:nodoc: # rubocop:disable Lint/DuplicateMethods
     return if context.nil? or context.zero?
 
     add_start = context > @start_old ? @start_old : context
+
     @start_old -= add_start
     @start_new -= add_start
 
+    old_size = @data_old.size
+
     add_end =
-      if (@end_old + context) > @data_old.size
-        @data_old.size - @end_old
+      if (@end_old + context) > old_size
+        old_size - @end_old
       else
         context
       end
 
-    add_end = @max_diff_size if add_end > @max_diff_size
+    add_end = @max_diff_size if add_end >= old_size
 
     @end_old += add_end
     @end_new += add_end

spec/fixtures/ldiff/output.diff.chef-u

@@ -0,0 +1,8 @@
+--- spec/fixtures/old-chef	2020-06-23 21:57:15.000000000 -0400
++++ spec/fixtures/new-chef	2020-06-23 21:57:29.000000000 -0400
+@@ -1,5 +1,5 @@
+ {
+   "name": "x",
+-  "description": "hi"
++  "description": "lo"
+ }

spec/fixtures/new-chef

@@ -0,0 +1,4 @@
+{
+  "name": "x",
+  "description": "lo"
+}

spec/fixtures/old-chef

@@ -0,0 +1,4 @@
+{
+  "name": "x",
+  "description": "hi"
+}

spec/issues_spec.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
+require 'diff/lcs/hunk'
 
 describe 'Diff::LCS Issues' do
   include Diff::LCS::SpecHelper::Matchers
@@ -64,4 +65,34 @@
       }.to raise_error(RSpec::Expectations::ExpectationNotMetError)
     end
   end
+
+  describe "issue #60" do
+    it 'should produce unified output with correct context' do
+      old_data = <<-DATA_OLD.strip.split("\n").map(&:chomp)
+{
+  "name": "x",
+  "description": "hi"
+}
+      DATA_OLD
+
+      new_data = <<-DATA_NEW.strip.split("\n").map(&:chomp)
+{
+  "name": "x",
+  "description": "lo"
+}
+      DATA_NEW
+
+      diff = ::Diff::LCS.diff(old_data, new_data)
+      hunk = ::Diff::LCS::Hunk.new(old_data, new_data, diff.first, 3, 0)
+
+      expect(hunk.diff(:unified)).to eq(<<-EXPECTED.chomp)
+@@ -1,5 +1,5 @@
+ {
+   "name": "x",
+-  "description": "hi"
++  "description": "lo"
+ }
+      EXPECTED
+    end
+  end
 end

spec/ldiff_spec.rb

@@ -10,6 +10,11 @@
   let(:output_diff_e) { read_fixture('-e') }
   let(:output_diff_f) { read_fixture('-f') }
   let(:output_diff_u) { read_fixture('-u') }
+  let(:output_diff_chef) { read_fixture('-u', base: 'output.diff.chef')}
+
+  specify do
+    expect(run_ldiff('-u', left: 'old-chef', right: 'new-chef')).to eq(output_diff_chef)
+  end
 
   specify do
     expect(run_ldiff).to eq(output_diff)
@@ -31,8 +36,8 @@
     expect(run_ldiff('-u')).to eq(output_diff_u)
   end
 
-  def read_fixture(flag = nil)
-    clean_data(IO.binread("spec/fixtures/ldiff/output.diff#{flag}"), flag)
+  def read_fixture(flag = nil, base: 'output.diff')
+    clean_data(IO.binread("spec/fixtures/ldiff/#{base}#{flag}"), flag)
   end
 
   def clean_data(data, flag)