From 3c359cadb9f968db6e9f78b277928b877a16a04c Mon Sep 17 00:00:00 2001
From: Lin Jen-Shin <godfat@godfat.org>
Date: Mon, 15 May 2017 21:35:42 +0800
Subject: Scan trace lines from bottom up for parsing coverage

So that it stops at the last coverage pattern, instead of the first,
and we still not reading the whole trace if possible.
---
 lib/gitlab/ci/trace/stream.rb           | 41 +++++++++++++++++++++++++--------
 spec/lib/gitlab/ci/trace/stream_spec.rb |  2 +-
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/lib/gitlab/ci/trace/stream.rb b/lib/gitlab/ci/trace/stream.rb
index fa462cbe095..2bb7a5bad35 100644
--- a/lib/gitlab/ci/trace/stream.rb
+++ b/lib/gitlab/ci/trace/stream.rb
@@ -73,7 +73,7 @@ module Gitlab
 
           match = ""
 
-          stream.each_line do |line|
+          reverse_line do |line|
             matches = line.scan(regex)
             next unless matches.is_a?(Array)
             next if matches.empty?
@@ -85,19 +85,23 @@ module Gitlab
 
           nil
         rescue
-          # if bad regex or something goes wrong we dont want to interrupt transition
-          # so we just silentrly ignore error for now
+          # if bad regex or something goes wrong we don't want to interrupt transition
+          # so we just silently ignore error for now
         end
 
         private
 
-        def read_last_lines(last_lines)
-          chunks = []
-          pos = lines = 0
+        def read_last_lines(last_lines = nil)
+          to_enum(:reverse_line, last_lines).reverse_each.to_a.join
+        end
+
+        def reverse_line(last_lines = nil, &block)
+          leftover = ''
+          pos = read_lines = 0
           max = stream.size
 
           # We want an extra line to make sure fist line has full contents
-          while lines <= last_lines && pos < max
+          while pos < max && (last_lines.nil? || last_lines > 0)
             pos += BUFFER_SIZE
 
             buf =
@@ -109,11 +113,28 @@ module Gitlab
                 stream.read(BUFFER_SIZE - (pos - max))
               end
 
-            lines += buf.count("\n")
-            chunks.unshift(buf)
+            read_lines += buf.count("\n")
+
+            next_partial_line, *current_lines = buf.lines
+            *complete_lines, partial_line = current_lines
+            complete_lines << "#{partial_line}#{leftover}"
+
+            if last_lines
+              complete_lines.last(last_lines)
+            else
+              complete_lines
+            end.reverse_each(&block)
+
+            last_lines -= complete_lines.size if last_lines
+            leftover = next_partial_line
           end
 
-          chunks.join.lines.last(last_lines).join
+          # Handle the leftover
+          if last_lines && last_lines > 0
+            leftover.lines.last(last_lines).reverse_each(&block)
+          elsif last_lines.nil?
+            leftover.lines.reverse_each(&block)
+          end
         end
       end
     end
diff --git a/spec/lib/gitlab/ci/trace/stream_spec.rb b/spec/lib/gitlab/ci/trace/stream_spec.rb
index 40ac5a3ed37..4d2d8327655 100644
--- a/spec/lib/gitlab/ci/trace/stream_spec.rb
+++ b/spec/lib/gitlab/ci/trace/stream_spec.rb
@@ -240,7 +240,7 @@ describe Gitlab::Ci::Trace::Stream do
     end
 
     context 'multiple results in content & regex' do
-      let(:data) { ' (98.39%) covered. (98.29%) covered' }
+      let(:data) { " (98.39%) covered.\n (98.29%) covered" }
       let(:regex) { '\(\d+.\d+\%\) covered' }
 
       it { is_expected.to eq("98.29") }
-- 
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