Add latest changes from gitlab-org/gitlab@13-9-stable-eev13.9.0-rc42

6 files changed, 124 insertions, 25 deletions

diff --git a/lib/gitlab/diff/char_diff.rb b/lib/gitlab/diff/char_diff.rb
new file mode 100644
index 00000000000..c8bb39e9f5d
--- /dev/null
+++ b/lib/gitlab/diff/char_diff.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Diff
+    class CharDiff
+      include Gitlab::Utils::StrongMemoize
+
+      def initialize(old_string, new_string)
+        @old_string = old_string.to_s
+        @new_string = new_string.to_s
+        @changes = []
+      end
+
+      def generate_diff
+        @changes = diff_match_patch.diff_main(@old_string, @new_string)
+        diff_match_patch.diff_cleanupSemantic(@changes)
+
+        @changes
+      end
+
+      def changed_ranges(offset: 0)
+        old_diffs = []
+        new_diffs = []
+        new_pointer = old_pointer = offset
+
+        generate_diff.each do |(action, content)|
+          content_size = content.size
+
+          if action == :equal
+            new_pointer += content_size
+            old_pointer += content_size
+          end
+
+          if action == :delete
+            old_diffs << (old_pointer..(old_pointer + content_size - 1))
+            old_pointer += content_size
+          end
+
+          if action == :insert
+            new_diffs << (new_pointer..(new_pointer + content_size - 1))
+            new_pointer += content_size
+          end
+        end
+
+        [old_diffs, new_diffs]
+      end
+
+      def to_html
+        @changes.map do |op, text|
+          %{<span class="#{html_class_names(op)}">#{ERB::Util.html_escape(text)}</span>}
+        end.join.html_safe
+      end
+
+      private
+
+      def diff_match_patch
+        strong_memoize(:diff_match_patch) { DiffMatchPatch.new }
+      end
+
+      def html_class_names(operation)
+        class_names = ['idiff']
+
+        case operation
+        when :insert
+          class_names << 'addition'
+        when :delete
+          class_names << 'deletion'
+        end
+
+        class_names.join(' ')
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/diff/file_collection/base.rb b/lib/gitlab/diff/file_collection/base.rb
index 8f4f8febec0..627abfbfe7e 100644
--- a/lib/gitlab/diff/file_collection/base.rb
+++ b/lib/gitlab/diff/file_collection/base.rb
@@ -117,7 +117,7 @@ module Gitlab
         end
 
         def sort_diffs(diffs)
-          return diffs unless Feature.enabled?(:sort_diffs, project, default_enabled: false)
+          return diffs unless Feature.enabled?(:sort_diffs, project, default_enabled: :yaml)
 
           Gitlab::Diff::FileCollectionSorter.new(diffs).sort
         end
diff --git a/lib/gitlab/diff/file_collection_sorter.rb b/lib/gitlab/diff/file_collection_sorter.rb
index 94626875580..7b099543c83 100644
--- a/lib/gitlab/diff/file_collection_sorter.rb
+++ b/lib/gitlab/diff/file_collection_sorter.rb
@@ -3,6 +3,10 @@
 module Gitlab
   module Diff
     class FileCollectionSorter
+      B_FOLLOWS_A = 1
+      A_FOLLOWS_B = -1
+      EQUIVALENT = 0
+
       attr_reader :diffs
 
       def initialize(diffs)
@@ -29,14 +33,16 @@ module Gitlab
         a_part = a_parts.shift
         b_part = b_parts.shift
 
-        return 1 if a_parts.size < b_parts.size && a_parts.empty?
-        return -1 if a_parts.size > b_parts.size && b_parts.empty?
+        return B_FOLLOWS_A if a_parts.size < b_parts.size && a_parts.empty?
+        return A_FOLLOWS_B if a_parts.size > b_parts.size && b_parts.empty?
 
         comparison = a_part <=> b_part
 
-        return comparison unless comparison == 0
+        return comparison unless comparison == EQUIVALENT
+        return compare_path_parts(a_parts, b_parts) if a_parts.any? && b_parts.any?
 
-        compare_path_parts(a_parts, b_parts)
+        # If A and B have the same name (e.g. symlink change), they are identical so return 0
+        EQUIVALENT
       end
     end
   end
diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
index a5259079345..035084d4861 100644
--- a/lib/gitlab/diff/highlight.rb
+++ b/lib/gitlab/diff/highlight.rb
@@ -3,12 +3,13 @@
 module Gitlab
   module Diff
     class Highlight
-      attr_reader :diff_file, :diff_lines, :raw_lines, :repository
+      attr_reader :diff_file, :diff_lines, :raw_lines, :repository, :project
 
       delegate :old_path, :new_path, :old_sha, :new_sha, to: :diff_file, prefix: :diff
 
       def initialize(diff_lines, repository: nil)
         @repository = repository
+        @project = repository&.project
 
         if diff_lines.is_a?(Gitlab::Diff::File)
           @diff_file = diff_lines
@@ -66,7 +67,7 @@ module Gitlab
       end
 
       def inline_diffs
-        @inline_diffs ||= InlineDiff.for_lines(@raw_lines)
+        @inline_diffs ||= InlineDiff.for_lines(@raw_lines, project: project)
       end
 
       def old_lines
diff --git a/lib/gitlab/diff/highlight_cache.rb b/lib/gitlab/diff/highlight_cache.rb
index 90cb9c8638a..7932cd2a837 100644
--- a/lib/gitlab/diff/highlight_cache.rb
+++ b/lib/gitlab/diff/highlight_cache.rb
@@ -8,6 +8,7 @@ module Gitlab
 
       EXPIRATION = 1.week
       VERSION = 1
+      NEXT_VERSION = 2
 
       delegate :diffable,     to: :@diff_collection
       delegate :diff_options, to: :@diff_collection
@@ -69,12 +70,20 @@ module Gitlab
 
       def key
         strong_memoize(:redis_key) do
-          ['highlighted-diff-files', diffable.cache_key, VERSION, diff_options].join(":")
+          ['highlighted-diff-files', diffable.cache_key, version, diff_options].join(":")
         end
       end
 
       private
 
+      def version
+        if Feature.enabled?(:improved_merge_diff_highlighting, diffable.project, default_enabled: :yaml)
+          NEXT_VERSION
+        else
+          VERSION
+        end
+      end
+
       def set_highlighted_diff_lines(diff_file, content)
         diff_file.highlighted_diff_lines = content.map do |line|
           Gitlab::Diff::Line.safe_init_from_hash(line)
diff --git a/lib/gitlab/diff/inline_diff.rb b/lib/gitlab/diff/inline_diff.rb
index 5815d1bae4a..cf769262958 100644
--- a/lib/gitlab/diff/inline_diff.rb
+++ b/lib/gitlab/diff/inline_diff.rb
@@ -27,28 +27,19 @@ module Gitlab
         @offset = offset
       end
 
-      def inline_diffs
+      def inline_diffs(project: nil)
         # Skip inline diff if empty line was replaced with content
         return if old_line == ""
 
-        lcp = longest_common_prefix(old_line, new_line)
-        lcs = longest_common_suffix(old_line[lcp..-1], new_line[lcp..-1])
-
-        lcp += offset
-        old_length = old_line.length + offset
-        new_length = new_line.length + offset
-
-        old_diff_range = lcp..(old_length - lcs - 1)
-        new_diff_range = lcp..(new_length - lcs - 1)
-
-        old_diffs = [old_diff_range] if old_diff_range.begin <= old_diff_range.end
-        new_diffs = [new_diff_range] if new_diff_range.begin <= new_diff_range.end
-
-        [old_diffs, new_diffs]
+        if Feature.enabled?(:improved_merge_diff_highlighting, project, default_enabled: :yaml)
+          CharDiff.new(old_line, new_line).changed_ranges(offset: offset)
+        else
+          deprecated_diff
+        end
       end
 
       class << self
-        def for_lines(lines)
+        def for_lines(lines, project: nil)
           changed_line_pairs = find_changed_line_pairs(lines)
 
           inline_diffs = []
@@ -57,7 +48,7 @@ module Gitlab
             old_line = lines[old_index]
             new_line = lines[new_index]
 
-            old_diffs, new_diffs = new(old_line, new_line, offset: 1).inline_diffs
+            old_diffs, new_diffs = new(old_line, new_line, offset: 1).inline_diffs(project: project)
 
             inline_diffs[old_index] = old_diffs
             inline_diffs[new_index] = new_diffs
@@ -97,6 +88,24 @@ module Gitlab
 
       private
 
+      # See: https://gitlab.com/gitlab-org/gitlab/-/issues/299884
+      def deprecated_diff
+        lcp = longest_common_prefix(old_line, new_line)
+        lcs = longest_common_suffix(old_line[lcp..-1], new_line[lcp..-1])
+
+        lcp += offset
+        old_length = old_line.length + offset
+        new_length = new_line.length + offset
+
+        old_diff_range = lcp..(old_length - lcs - 1)
+        new_diff_range = lcp..(new_length - lcs - 1)
+
+        old_diffs = [old_diff_range] if old_diff_range.begin <= old_diff_range.end
+        new_diffs = [new_diff_range] if new_diff_range.begin <= new_diff_range.end
+
+        [old_diffs, new_diffs]
+      end
+
       def longest_common_prefix(a, b) # rubocop:disable Naming/UncommunicativeMethodParamName
         max_length = [a.length, b.length].max