After Trace#limit, we seek to the next line in case

of breaking ANSI sequence or Unicode

lib/gitlab/ci/trace/stream.rb

@@ -30,6 +30,7 @@ module Gitlab
             last_bytes = stream_size
           end
           stream.seek(-last_bytes, IO::SEEK_END)
+          stream.readline
         end
 
         def append(data, offset)

spec/fixtures/trace/ansi-sequence-and-unicode

+.
+..
+😺
+ヾ(´༎ຶД༎ຶ`)ﾉ
+許功蓋

spec/lib/gitlab/ci/trace/stream_spec.rb

@@ -21,7 +21,7 @@ describe Gitlab::Ci::Trace::Stream do
       end
     end
 
-    it 'if size is larger we start from beggining' do
+    it 'if size is larger we start from beginning' do
       stream.limit(10)
 
       expect(stream.tell).to eq(0)
@@ -32,6 +32,26 @@ describe Gitlab::Ci::Trace::Stream do
 
       expect(stream.tell).to eq(6)
     end
+
+    context 'when the trace contains ANSI sequence and Unicode' do
+      let(:stream) do
+        described_class.new do
+          File.open(expand_fixture_path('trace/ansi-sequence-and-unicode'))
+        end
+      end
+
+      it 'forwards to the next linefeed, case 1' do
+        stream.limit(7)
+
+        expect(stream.raw).to eq('')
+      end
+
+      it 'forwards to the next linefeed, case 2' do
+        stream.limit(29)
+
+        expect(stream.raw).to eq("\e[01;32m許功蓋\e[0m\n")
+      end
+    end
   end
 
   describe '#append' do

spec/support/fixture_helpers.rb

 module FixtureHelpers
   def fixture_file(filename)
     return '' if filename.blank?
-    file_path = File.expand_path(Rails.root.join('spec/fixtures/', filename))
-    File.read(file_path)
+    File.read(expand_fixture_path(filename))
+  end
+
+  def expand_fixture_path(filename)
+    File.expand_path(Rails.root.join('spec/fixtures/', filename))
   end
 end