protect against no data

2 files changed, 15 insertions, 1 deletions

diff --git a/lib/diff/lcs/hunk.rb b/lib/diff/lcs/hunk.rb
index 6c5ea6a..05c3fb6 100644
--- a/lib/diff/lcs/hunk.rb
+++ b/lib/diff/lcs/hunk.rb
@@ -12,7 +12,7 @@ class Diff::LCS::Hunk
     # At first, a hunk will have just one Block in it
     @blocks = [ Diff::LCS::Block.new(piece) ]
     if String.method_defined?(:encoding)
-      @preferred_data_encoding = data_old[0].encoding
+      @preferred_data_encoding = data_old.fetch(0, data_new.fetch(0,'') ).encoding
     end
     @data_old = data_old
     @data_new = data_new
diff --git a/spec/hunk_spec.rb b/spec/hunk_spec.rb
index 0741b87..282946b 100644
--- a/spec/hunk_spec.rb
+++ b/spec/hunk_spec.rb
@@ -59,5 +59,19 @@ Tu avec carte {count} item has
 EOD
       expect(hunk.diff(:reverse_ed).to_s == expected).to eql true
     end
+
+    context 'with empty first data set' do
+      let(:old_data) { [] }
+
+      it 'should be able to produce a unified diff' do
+        expected =
+(<<-EOD.encode('UTF-16LE').chomp)
+@@ -1 +1,2 @@
++Tu avec carte {count} item has
+EOD
+        expect(hunk.diff(:unified).to_s == expected).to eql true
+      end
+    end
+
   end
 end