take nonewline context into account in diff parser

app/views/projects/diffs/_line.html.haml

@@ -9,7 +9,7 @@
   - case type
   - when 'match'
     = diff_match_line line.old_pos, line.new_pos, text: line.text
-  - when 'nonewline'
+  - when 'old-nonewline', 'new-nonewline'
     %td.old_line.diff-line-num
     %td.new_line.diff-line-num
     %td.line_content.match= line.text

app/views/projects/diffs/_parallel_view.html.haml

@@ -12,7 +12,7 @@
           - case left.type
           - when 'match'
             = diff_match_line left.old_pos, nil, text: left.text, view: :parallel
-          - when 'nonewline'
+          - when 'old-nonewline', 'new-nonewline'
             %td.old_line.diff-line-num
             %td.line_content.match= left.text
           - else
@@ -31,7 +31,7 @@
           - case right.type
           - when 'match'
             = diff_match_line nil, right.new_pos, text: left.text, view: :parallel
-          - when 'nonewline'
+          - when 'old-nonewline', 'new-nonewline'
             %td.new_line.diff-line-num
             %td.line_content.match= right.text
           - else

lib/gitlab/diff/line.rb

@@ -38,11 +38,11 @@ module Gitlab
       end
       def added?
-        type == 'new'
+        type == 'new' || type == 'new-nonewline'
       end
       def removed?
-        type == 'old'
+        type == 'old' || type == 'old-nonewline'
       end
       def rich_text
@@ -52,7 +52,7 @@ module Gitlab
       end
       def meta?
-        type == 'match' || type == 'nonewline'
+        type == 'match'
       end
       def as_json(opts = nil)

lib/gitlab/diff/parser.rb

@@ -11,6 +11,7 @@ module Gitlab
         line_old = 1
         line_new = 1
         type = nil
+        context = nil
         # By returning an Enumerator we make it possible to search for a single line (with #find)
         # without having to instantiate all the others that come after it.
@@ -31,7 +32,8 @@ module Gitlab
               line_obj_index += 1
               next
             elsif line[0] == '\\'
-              type = 'nonewline'
+              type = "#{context}-nonewline"
+
               yielder << Gitlab::Diff::Line.new(full_line, type, line_obj_index, line_old, line_new)
               line_obj_index += 1
             else
@@ -43,8 +45,10 @@ module Gitlab
             case line[0]
             when "+"
               line_new += 1
+              context = :new
             when "-"
               line_old += 1
+              context = :old
             when "\\" # rubocop:disable Lint/EmptyWhen
               # No increment
             else

spec/lib/gitlab/diff/parser_spec.rb

@@ -91,6 +91,54 @@ eos
     end
   end
+  describe '\ No newline at end of file' do
+    it "parses nonewline in one file correctly" do
+      first_nonewline_diff = <<~END
+        --- a/test
+        +++ b/test
+        @@ -1,2 +1,2 @@
+        +ipsum
+         lorem
+        -ipsum
+        \\ No newline at end of file
+      END
+      lines = parser.parse(first_nonewline_diff.lines).to_a
+
+      expect(lines[0].type).to eq('new')
+      expect(lines[0].text).to eq('+ipsum')
+      expect(lines[2].type).to eq('old')
+      expect(lines[3].type).to eq('old-nonewline')
+      expect(lines[1].old_pos).to eq(1)
+      expect(lines[1].new_pos).to eq(2)
+    end
+
+    it "parses nonewline in two files correctly" do
+      both_nonewline_diff = <<~END
+        --- a/test
+        +++ b/test
+        @@ -1,2 +1,2 @@
+        -lorem
+        -ipsum
+        \\ No newline at end of file
+        +ipsum
+        +lorem
+        \\ No newline at end of file
+      END
+      lines = parser.parse(both_nonewline_diff.lines).to_a
+
+      expect(lines[0].type).to eq('old')
+      expect(lines[1].type).to eq('old')
+      expect(lines[2].type).to eq('old-nonewline')
+      expect(lines[5].type).to eq('new-nonewline')
+      expect(lines[3].text).to eq('+ipsum')
+      expect(lines[3].old_pos).to eq(3)
+      expect(lines[3].new_pos).to eq(1)
+      expect(lines[4].text).to eq('+lorem')
+      expect(lines[4].old_pos).to eq(3)
+      expect(lines[4].new_pos).to eq(2)
+    end
+  end
+
   context 'when lines is empty' do
     it { expect(parser.parse([])).to eq([]) }
     it { expect(parser.parse(nil)).to eq([]) }