Only consider the lengths of the relevant parts when --nth is set

src/item.go

@@ -63,7 +63,16 @@ func (i *Item) Rank(cache bool) Rank {
 	var tiebreak uint16
 	switch rankTiebreak {
 	case byLength:
+		// It is guaranteed that .transformed in not null in normal execution
+		if i.transformed != nil {
+			lenSum := 0
+			for _, token := range *i.transformed {
+				lenSum += len(*token.text)
+			}
+			tiebreak = uint16(lenSum)
+		} else {
 			tiebreak = uint16(len(*i.text))
+		}
 	case byBegin:
 		// We can't just look at i.offsets[0][0] because it can be an inverse term
 		tiebreak = uint16(minBegin)

test/test_go.rb

@@ -501,6 +501,32 @@ class TestGoFZF < TestBase
     assert_equal input, `cat #{tempname} | #{FZF} -f"!z" -x --tiebreak end`.split($/)
   end
 
+  def test_tiebreak_length_with_nth
+    input = %w[
+      1:hell
+      123:hello
+      12345:he
+      1234567:h
+    ]
+    writelines tempname, input
+
+    output = %w[
+      1:hell
+      12345:he
+      123:hello
+      1234567:h
+    ]
+    assert_equal output, `cat #{tempname} | #{FZF} -fh`.split($/)
+
+    output = %w[
+      1234567:h
+      12345:he
+      1:hell
+      123:hello
+    ]
+    assert_equal output, `cat #{tempname} | #{FZF} -fh -n2 -d:`.split($/)
+  end
+
   def test_invalid_cache
     tmux.send_keys "(echo d; echo D; echo x) | #{fzf '-q d'}", :Enter
     tmux.until { |lines| lines[-2].include? '2/3' }