Adding basic find_by_id functionality to Language

lib/linguist/language.rb

@@ -24,6 +24,7 @@ module Linguist
     @index              = {}
     @name_index         = {}
     @alias_index        = {}
+    @language_id_index  = {}
 
     @extension_index          = Hash.new { |h,k| h[k] = [] }
     @interpreter_index        = Hash.new { |h,k| h[k] = [] }
@@ -84,6 +85,8 @@ module Linguist
         @filename_index[filename] << language
       end
 
+      @language_id_index[language.language_id] = language
+
       language
     end
 
@@ -193,6 +196,19 @@ module Linguist
       @interpreter_index[interpreter]
     end
 
+    # Public: Look up Languages by its language_id.
+    #
+    # language_id - Integer of language_id
+    #
+    # Examples
+    #
+    #   Language.find_by_id(100)
+    #   # => [#<Language name="Elixir">]
+    #
+    # Returns the matching Language
+    def self.find_by_id(language_id)
+      @language_id_index[language_id.to_i]
+    end
 
     # Public: Look up Language by its name.
     #

test/test_language.rb

@@ -77,6 +77,12 @@ class TestLanguage < Minitest::Test
     assert_equal 421, Language['xBase'].language_id
   end
 
+  def test_find_by_id
+    assert_equal Language['Elixir'], Language.find_by_id(100)
+    assert_equal Language['Ruby'], Language.find_by_id(326)
+    assert_equal Language['xBase'], Language.find_by_id(421)
+  end
+
   def test_groups
     # Test a couple identity cases
     assert_equal Language['Perl'], Language['Perl'].group