Add Language#find_by_lexer

lib/linguist/language.rb

@@ -3,6 +3,7 @@ require 'yaml'
 module Linguist
   class Language
     @name_index      = {}
+    @lexer_index     = {}
     @extension_index = {}
 
     def self.create(attributes = {})
@@ -10,6 +11,10 @@ module Linguist
 
       @name_index[language.name.downcase] = language
 
+      if language.default_lexer? || !@lexer_index.key?(language.lexer)
+        @lexer_index[language.lexer] = language
+      end
+
       language.extensions.each do |extension|
         @extension_index[extension] = language
         @extension_index[extension.sub(/^./, '')] = language
@@ -44,6 +49,10 @@ module Linguist
       find_by_extension(ext)
     end
 
+    def self.find_by_lexer(lexer)
+      @lexer_index[lexer]
+    end
+
     def initialize(attributes = {})
       @name       = attributes[:name] || raise(ArgumentError, "missing name")
       @lexer      = attributes[:lexer] || default_lexer
@@ -55,6 +64,10 @@ module Linguist
     def default_lexer
       name.downcase.gsub(/\s/, '-')
     end
+
+    def default_lexer?
+      lexer == default_lexer
+    end
   end
 
   YAML.load_file(File.expand_path("../extensions.yml", __FILE__)).each do |name, options|

test/test_language.rb

@@ -32,6 +32,15 @@ class TestLanguage < Test::Unit::TestCase
     assert_equal ruby, Language.find_by_filename('./Rakefile')
   end
 
+  def test_find_by_lexer
+    assert_equal Language['Perl'], Language.find_by_lexer('perl')
+    assert_equal Language['Python'], Language.find_by_lexer('python')
+    assert_equal Language['Ruby'], Language.find_by_lexer('ruby')
+    assert_equal Language['C++'], Language.find_by_lexer('cpp')
+    assert_equal Language['JavaScript'], Language.find_by_lexer('javascript')
+    assert_equal Language['Scheme'], Language.find_by_lexer('scheme')
+  end
+
   def test_name
     assert_equal "Perl",   Language['Perl'].name
     assert_equal "Python", Language['Python'].name