Require primary extension to be set

lib/linguist/language.rb

@@ -295,11 +295,17 @@ module Linguist
     # Returns the extensions Array
     attr_reader :extensions
 
-    # Public: Get primary extension
+    # Deprecated: Get primary extension
     #
     # Defaults to the first extension but can be overriden
     # in the languages.yml.
     #
+    # The primary extension can not be nil. Tests should verify this.
+    #
+    # This attribute is only used by app/helpers/gists_helper.rb for
+    # creating the language dropdown. It really should be using `name`
+    # instead. Would like to drop primary extension.
+    #
     # Returns the extension String.
     attr_reader :primary_extension
 

lib/linguist/languages.yml

@@ -547,6 +547,7 @@ Max/MSP:
 
 MiniD: # Legacy
   searchable: false
+  primary_extension: .minid # Dummy extension
 
 Mirah:
   type: programming

test/test_language.rb

@@ -277,6 +277,12 @@ class TestLanguage < Test::Unit::TestCase
     assert_equal '.pl', Language['Perl'].primary_extension
     assert_equal '.py', Language['Python'].primary_extension
     assert_equal '.rb', Language['Ruby'].primary_extension
+
+    # This is a nasty requirement, but theres some code in GitHub that
+    # expects this. Really want to drop this.
+    Language.all.each do |language|
+      assert language.primary_extension, "#{language} has no primary extension"
+    end
   end
 
   def test_eql