Make autoprefixer dependency optional

See #277

Author: glebm

README.md

@@ -32,6 +32,9 @@ This gem requires a Sass engine, so make sure you have **one** of these two gems
 
 Also ensure that `sprockets-rails` is at least v2.3.2.
 
+For wider browser compatibility, use [Autoprefixer][autoprefixer].
+If you are using Rails, add the `autoprefixer-rails` gem to your app and ensure you have a JavaScript runtime (e.g. NodeJS).
+
 `bundle install` and restart your server to make the files available through the pipeline.
 
 Import Bootstrap styles in `app/assets/stylesheets/application.scss`:
@@ -113,14 +116,6 @@ Refer to your framework's documentation on the subject.
 
 ## Configuration
 
-### Sass: Autoprefixer
-
-Bootstrap requires the use of [Autoprefixer][autoprefixer].
-[Autoprefixer][autoprefixer] adds vendor prefixes to CSS rules using values from [Can I Use](http://caniuse.com/).
-
-If you are using bootstrap with Rails, autoprefixer is set up for you automatically.
-Otherwise, please consult the [Autoprefixer documentation][autoprefixer].
-
 ### Sass: Individual components
 
 By default all of Bootstrap is imported.

Rakefile

@@ -57,7 +57,6 @@ task :debug do
   end
   require './lib/bootstrap'
   require 'term/ansicolor'
-  require 'autoprefixer-rails'
   path = Bootstrap.stylesheets_path
   %w(_bootstrap _bootstrap-reboot _bootstrap-grid).each do |file|
     filename = "#{path}/#{file}.scss"
@@ -66,7 +65,6 @@ task :debug do
           else
             Sass.compile(filename).css
           end
-    css = AutoprefixerRails.process(css)
     out = File.join('tmp', "#{file[1..-1]}.css")
     File.write(out, css)
     $stderr.puts Term::ANSIColor.green "Compiled #{out}"

bootstrap.gemspec

@@ -15,7 +15,6 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 2.3.3'
 
   s.add_runtime_dependency 'popper_js', '>= 2.11.8', '< 3'
-  s.add_runtime_dependency 'autoprefixer-rails', '>= 9.1.0'
 
   s.add_development_dependency 'rake'
 

lib/bootstrap/engine.rb

@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require 'autoprefixer-rails'
 begin
   require 'dartsass-sprockets'
 rescue LoadError

test/dummy_rails/config/application.rb

@@ -10,7 +10,6 @@
   require "#{framework}/railtie"
 end
 
-require 'autoprefixer-rails'
 require 'uglifier'
 require 'bootstrap'
 
@@ -29,4 +28,3 @@ class Application < Rails::Application
     end
   end
 end
-

test/gemfiles/rails_5_0.gemfile

@@ -2,7 +2,6 @@ source 'https://rubygems.org'
 
 gem 'actionpack', '~> 5.0.0'
 gem 'activesupport', '~> 5.0.0'
-gem 'autoprefixer-rails', '>= 6.3.6.1'
 gem 'sassc-rails', '~> 2.0'
 
 gemspec path: '../../'

test/gemfiles/rails_5_1.gemfile

@@ -2,7 +2,6 @@ source 'https://rubygems.org'
 
 gem 'actionpack', '~> 5.1.0'
 gem 'activesupport', '~> 5.1.0'
-gem 'autoprefixer-rails', '>= 7.1.1'
 gem 'sassc-rails', '~> 2.0'
 
 gemspec path: '../../'

test/gemfiles/rails_5_2.gemfile

@@ -2,7 +2,6 @@ source 'https://rubygems.org'
 
 gem 'actionpack', '~> 5.2.8'
 gem 'activesupport', '~> 5.2.8'
-gem 'autoprefixer-rails', '>= 7.1.1'
 gem 'sassc-rails', '~> 2.0'
 
 gemspec path: '../../'

test/gemfiles/rails_6_0.gemfile

@@ -2,7 +2,6 @@ source 'https://rubygems.org'
 
 gem 'actionpack', '~> 6.0.3'
 gem 'activesupport', '~> 6.0.3'
-gem 'autoprefixer-rails', '>= 9.7.6'
 gem 'sassc-rails', '~> 2.0'
 
 gemspec path: '../../'

test/gemfiles/rails_6_1.gemfile

@@ -2,7 +2,6 @@ source 'https://rubygems.org'
 
 gem 'actionpack', '~> 6.1.3'
 gem 'activesupport', '~> 6.1.3'
-gem 'autoprefixer-rails', '>= 9.7.6'
 gem 'sassc-rails', '~> 2.0'
 
 gemspec path: '../../'