[PATCH] encoding: use CharlockHolmes properly on first run

[Eric Wong]

Ruby case/when is not like C with fall-through, so we can't
rely on fall-through behavior to use CharlockHolmes to detect
legacy encodings.
---
 lib/dtas/encoding.rb | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/lib/dtas/encoding.rb b/lib/dtas/encoding.rb
index dad54af..bbc6076 100644
--- a/lib/dtas/encoding.rb
+++ b/lib/dtas/encoding.rb
@@ -11,15 +11,14 @@ def self.extended(mod)
 private
 
   def try_enc_harder(str, enc, old) # :nodoc:
+    begin
+      require 'charlock_holmes'
+      @charlock_holmes = CharlockHolmes::EncodingDetector.new
+    rescue LoadError
+      @charlock_holmes = false
+    end if @charlock_holmes.nil?
+
     case @charlock_holmes
-    when nil
-      begin
-        require 'charlock_holmes'
-        @charlock_holmes = CharlockHolmes::EncodingDetector.new
-      rescue LoadError
-        warn "`charlock_holmes` gem not available for encoding detection"
-        @charlock_holmes = false
-      end
     when false
       enc_fallback(str, enc, old)
     else