Remove nokogiri depencency and use ruby alpine base docker image

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.5.1
+FROM ruby:2.5.1-alpine
 
 # Fetch/install gems
 RUN mkdir -p /opt/gems

Gemfile

@@ -6,7 +6,6 @@ git_source(:github) { |repo_name| "https:/#{repo_name}" }
 
 gem 'bundler', '~> 1.16'
 gem 'haml'
-gem 'nokogiri'
 
 group :development, :test do
  gem 'rake', '~> 10.0'

Gemfile.lock

@@ -8,9 +8,6 @@ GEM
  temple (>= 0.8.0)
  tilt
  json (2.1.0)
- mini_portile2 (2.3.0)
- nokogiri (1.8.2)
- mini_portile2 (~> 2.3.0)
  parallel (1.12.1)
  parser (2.5.1.0)
  ast (~> 2.4.0)
@@ -53,7 +50,6 @@ PLATFORMS
 DEPENDENCIES
  bundler (~> 1.16)
  haml
- nokogiri
  rake (~> 10.0)
  rspec (~> 3.0)
  rubocop

lib/test_summary_buildkite_plugin/input.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
-require 'nokogiri'
+# We don't use nokogiri because we use an alpine-based docker image
+# And adding the required dependencies triples the size of the image
+require 'rexml/document'
 
 module TestSummaryBuildkitePlugin
  module Input
@@ -72,20 +74,20 @@ def crop
 
  class JUnit < Base
  def failures_raw
- files.map { |file| File.open(file) { |f| Nokogiri::XML(f, nil, encoding) } }
+ files.map { |file| REXML::Document.new(read(file)) }
  .map { |xml| xml_to_failures(xml) }
  .flatten
  end
 
  private
 
  def xml_to_failures(xml)
- xml.css('testcase').each_with_object([]) do |testcase, failures|
- testcase.css('failure').each do |failure|
+ xml.elements.enum_for(:each, '*/testcase').each_with_object([]) do |testcase, failures|
+ testcase.elements.each('failure') do |failure|
  failures << Failure::Structured.new(
- file: testcase['file'],
- name: testcase['name'],
- details: failure.inner_html
+ file: testcase.attributes['file'].to_s,
+ name: testcase.attributes['name'].to_s,
+ details: failure.text
  )
  end
  end

spec/test_summary_buildkite_plugin/input_spec.rb

@@ -66,10 +66,6 @@
  expect(input.failures.first.details).to start_with('Failure/Error: ')
  end
 
- it 'details escape html' do
- expect(input.failures.first.details).to include('<')
- end
-
  it 'failures have file' do
  expect(input.failures.first.file).to eq('./spec/lib/url_whitelist_spec.rb')
  end