[ruby/reline] Drop prompt list cache when num of lines is changed

https://github.com/ruby/reline/commit/1959e22043

lib/reline/line_editor.rb

@@ -50,6 +50,8 @@ class Reline::LineEditor
   CompletionJourneyData = Struct.new('CompletionJourneyData', :preposing, :postposing, :list, :pointer)
   MenuInfo = Struct.new('MenuInfo', :target, :list)
 
+  PROMPT_LIST_CACHE_TIMEOUT = 0.5
+
   def initialize(config, encoding)
     @config = config
     @completion_append_character = ''
@@ -78,7 +80,7 @@ class Reline::LineEditor
     end
     return [prompt, calculate_width(prompt, true), [prompt] * buffer.size] if simplified_rendering?
     if @prompt_proc
-      if @cached_prompt_list and Time.now.to_f < (@prompt_cache_time + 0.5)
+      if @cached_prompt_list and Time.now.to_f < (@prompt_cache_time + PROMPT_LIST_CACHE_TIMEOUT) and buffer.size == @cached_prompt_list.size
         prompt_list = @cached_prompt_list
       else
         prompt_list = @cached_prompt_list = @prompt_proc.(buffer)

test/reline/yamatanooroti/test_rendering.rb

@@ -398,6 +398,18 @@ begin
       EOC
     end
 
+    def test_prompt_list_caching
+      start_terminal(5, 30, %W{ruby -I#{@pwd}/lib #{@pwd}/bin/multiline_repl --prompt-list-cache-timeout 10 --dynamic-prompt}, startup_message: 'Multiline REPL.')
+      write("def hoge\n  3\nend")
+      close
+      assert_screen(<<~EOC)
+        Multiline REPL.
+        [0000]> def hoge
+        [0001]>   3
+        [0002]> end
+      EOC
+    end
+
     private def write_inputrc(content)
       File.open(@inputrc_file, 'w') do |f|
         f.write content