Add RubyParser helper class

Add helper class that encapsulates the `parser` and `astrolabe` gems so
that all linters need to do is call `parse_ruby` to get an AST.

Change-Id: I3ae6d7899766ff791ca8107593e115aae20ae97e
Reviewed-on: http://gerrit.causes.com/42570
Tested-by: jenkins <[email protected]>
Reviewed-by: Shane da Silva <[email protected]>

haml-lint.gemspec

@@ -26,5 +26,6 @@ Gem::Specification.new do |s|
   s.add_dependency 'sysexits', '~> 1.1'
 
   s.add_development_dependency 'rspec', '~> 3.0'
+  s.add_development_dependency 'rspec-its', '~> 1.0'
   s.add_development_dependency 'rubocop', '0.26.0' # Pin for Travis builds
 end

lib/haml_lint.rb

@@ -6,6 +6,7 @@
 require 'haml_lint/haml_visitor'
 require 'haml_lint/lint'
 require 'haml_lint/linter_registry'
+require 'haml_lint/ruby_parser'
 require 'haml_lint/linter'
 require 'haml_lint/logger'
 require 'haml_lint/reporter'

lib/haml_lint/linter.rb

@@ -9,6 +9,7 @@ class Linter
     def initialize(config)
       @config = config
       @lints = []
+      @ruby_parser = nil
     end
 
     def run(parser)
@@ -29,6 +30,14 @@ def add_lint(node, message = nil)
       @lints << Lint.new(self, parser.filename, node.line, message || self.message)
     end
 
+    # Parse Ruby code into an abstract syntax tree.
+    #
+    # @return [AST::Node]
+    def parse_ruby(source)
+      @ruby_parser ||= HamlLint::RubyParser.new
+      @ruby_parser.parse(source)
+    end
+
     # Remove the surrounding double quotes from a string, ignoring any
     # leading/trailing whitespace.
     #

lib/haml_lint/ruby_parser.rb

@@ -0,0 +1,29 @@
+require 'astrolabe/builder'
+require 'parser/current'
+
+module HamlLint
+  # Parser for the Ruby language.
+  #
+  # This provides a convenient wrapper around the `parser` gem and the
+  # `astrolabe` integration to go with it. It is intended to be used for linter
+  # checks that require deep inspection of Ruby code.
+  class RubyParser
+    # Creates a reusable parser.
+    def initialize
+      @builder = ::Astrolabe::Builder.new
+      @parser = ::Parser::CurrentRuby.new(@builder)
+    end
+
+    # Parse the given Ruby source into an abstract syntax tree.
+    #
+    # @param source [String] Ruby source code
+    # @return [Array] syntax tree in the form returned by Parser gem
+    def parse(source)
+      buffer = ::Parser::Source::Buffer.new('(string)')
+      buffer.source = source
+
+      @parser.reset
+      @parser.parse(buffer)
+    end
+  end
+end

spec/haml_lint/ruby_parser_spec.rb

@@ -0,0 +1,22 @@
+require 'spec_helper'
+
+describe HamlLint::RubyParser do
+  describe '#parse' do
+    subject { super().parse(source) }
+
+    context 'when given an empty string' do
+      let(:source) { '' }
+
+      it { should be_nil }
+    end
+
+    context 'when given a valid Ruby program' do
+      let(:source) { "puts 'Hello World'" }
+
+      it { should respond_to :children }
+      it { should respond_to :type }
+      it { should respond_to :parent }
+      its(:type) { should == :send }
+    end
+  end
+end

spec/spec_helper.rb

@@ -1,4 +1,5 @@
 require 'haml_lint'
+require 'rspec/its'
 
 Dir[File.dirname(__FILE__) + '/support/**/*.rb'].each { |f| require f }