Add Stylelint pre-commit hook (sds#590)

* Stylelint linter added in pre-hook

* CODE REVIEW

Author: Ruffeng

README.md

@@ -546,6 +546,7 @@ issue](https://github.com/brigade/overcommit/issues/238) for more details.
 * [SlimLint](lib/overcommit/hook/pre_commit/slim_lint.rb)
 * [Sqlint](lib/overcommit/hook/pre_commit/sqlint.rb)
 * [Standard](lib/overcommit/hook/pre_commit/standard.rb)
+* [StyleLint](lib/overcommit/hook/pre_commit/stylelint.rb)
 * [TrailingWhitespace](lib/overcommit/hook/pre_commit/trailing_whitespace.rb)
 * [TravisLint](lib/overcommit/hook/pre_commit/travis_lint.rb)
 * [TsLint](lib/overcommit/hook/pre_commit/ts_lint.rb)

config/default.yml

@@ -711,6 +711,17 @@ PreCommit:
     install_command: 'npm install -g standard'
     include: '**/*.js'
 
+  Stylelint:
+    enabled: false
+    description: 'Check styles with Stylelint'
+    require_executable: 'stylelint'
+    flags: ['-f', 'compact']
+    install_command: 'npm install -g stylelint'
+    include:
+      - '**/*.scss'
+      - '**/*.css'
+      - '**/*.less'
+
   TsLint:
       enabled: false
       description: 'Analyze with TSLint'

lib/overcommit/hook/pre_commit/stylelint.rb

@@ -0,0 +1,21 @@
+module Overcommit::Hook::PreCommit
+  # Runs `stylelint` against any modified CSS file.
+  #
+  # @see https://github.com/stylelint/stylelint
+  class Stylelint < Base
+    # example of output:
+    # index.css: line 4, col 4, error - Expected indentation of 2 spaces (indentation)
+
+    MESSAGE_REGEX = /^(?<file>.+):\D*(?<line>\d).*$/
+
+    def run
+      result = execute(command, args: applicable_files)
+      output = result.stdout.chomp
+      return :pass if result.success? && output.empty?
+      extract_messages(
+        output.split("\n"),
+        MESSAGE_REGEX
+      )
+    end
+  end
+end

spec/overcommit/hook/pre_commit/stylelint_spec.rb

@@ -0,0 +1,42 @@
+require 'spec_helper'
+
+describe Overcommit::Hook::PreCommit::Stylelint do
+  let(:config)  { Overcommit::ConfigurationLoader.default_configuration }
+  let(:context) { double('context') }
+  subject { described_class.new(config, context) }
+
+  before do
+    subject.stub(:applicable_files).and_return(%w[file1.scss file2.scss])
+  end
+
+  context 'when stylelint exits successfully' do
+    before do
+      result = double('result')
+      result.stub(:success?).and_return(true)
+      result.stub(:stdout).and_return('')
+      subject.stub(:execute).and_return(result)
+    end
+
+    it { should pass }
+  end
+
+  context 'when stylelint exits unsucessfully' do
+    let(:result) { double('result') }
+
+    before do
+      subject.stub(:execute).and_return(result)
+    end
+
+    context 'and it reports an error' do
+      before do
+        result.stub(:success?).and_return(false)
+        result.stub(:stdout).and_return([
+          'index.css: line 4, col 4, error - Expected indentation of 2 spaces (indentation)',
+          'form.css: line 10, col 6, error - Expected indentation of 4 spaces (indentation)',
+        ].join("\n"))
+      end
+
+      it { should fail_hook }
+    end
+  end
+end