Fix a bug with syntax highlighting

We need to refer to a lexer by alias, even if the lookup matched on
filename.

Fixes brightcove-archive#466.

Author: cespare

lib/syntax_highlighter.rb

@@ -1,9 +1,10 @@
 require "bundler/setup"
 require "pathological"
 
-require "pygments"
 require "lib/logging"
 require "lib/ruby_extensions"
+require "methodchain"
+require "pygments"
 
 class SyntaxHighlighter
   WEEK = 60*60*24*7
@@ -36,7 +37,7 @@ def colorize_blob(repo_name, file_type, blob)
   end
 
   def self.pygmentize(file_type, text)
-    file_type = "text" if Pygments::Lexer.find(file_type).nil?
+    file_type = Pygments::Lexer.find(file_type).then { |lexer| lexer[:aliases][0] rescue nil } || "text"
     Pygments.highlight(text, :lexer => file_type, :options => {
       :encoding => "utf-8", :nowrap => true, :stripnl => false, :stripall => false
     })

test/unit/syntax_highlighter_test.rb

@@ -0,0 +1,21 @@
+require File.expand_path(File.join(File.dirname(__FILE__), "../unit_test_helper.rb"))
+require "lib/syntax_highlighter.rb"
+
+class SyntaxHighlighterTest < Scope::TestCase
+  context "pygmentize" do
+    should "handle a language by alias" do
+      highlighted = SyntaxHighlighter.pygmentize("ruby", "foo")
+      assert_match /span/, highlighted
+    end
+
+    should "handle a language by filename" do
+      highlighted = SyntaxHighlighter.pygmentize("lisp", "foo")
+      assert_match /span/, highlighted
+    end
+
+    should "return plaintext for an unrecognized language" do
+      highlighted = SyntaxHighlighter.pygmentize("foobar", "foo")
+      assert_equal "foo", highlighted
+    end
+  end
+end