[ruby/reline] Implement `show-all-if-ambiguous` feature

(https://github.com/ruby/reline/pull/683)

https://github.com/ruby/reline/commit/0fe4fdc794

lib/reline/line_editor.rb

@@ -880,10 +880,12 @@ class Reline::LineEditor
           @completion_state = CompletionState::PERFECT_MATCH
         else
           @completion_state = CompletionState::MENU_WITH_PERFECT_MATCH
+          complete(list, true) if @config.show_all_if_ambiguous
         end
         @perfect_matched = completed
       else
         @completion_state = CompletionState::MENU
+        complete(list, true) if @config.show_all_if_ambiguous
       end
       if not just_show_list and target < completed
         @buffer_of_lines[@line_index] = (preposing + completed + completion_append_character.to_s + postposing).split("\n")[@line_index] || String.new(encoding: @encoding)

test/reline/yamatanooroti/multiline_repl

@@ -143,6 +143,11 @@ opt.on('--complete') {
     %w{String ScriptError SyntaxError Signal}.select{ |c| c.start_with?(target) }
   }
 }
+opt.on('--complete-menu-with-perfect-match') {
+  Reline.completion_proc = lambda { |target, preposing = nil, postposing = nil|
+    %w{abs abs2}.select{ |c| c.start_with?(target) }
+  }
+}
 opt.on('--autocomplete') {
   Reline.autocompletion = true
   Reline.completion_proc = lambda { |target, preposing = nil, postposing = nil|

test/reline/yamatanooroti/test_rendering.rb

@@ -1006,6 +1006,47 @@ begin
       EOC
     end
 
+    def test_completion_menu_is_displayed_horizontally
+      start_terminal(20, 50, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl --complete}, startup_message: 'Multiline REPL.')
+      write("S\t\t")
+      close
+      assert_screen(<<~'EOC')
+        Multiline REPL.
+        prompt> S
+        ScriptError  String
+        Signal       SyntaxError
+      EOC
+    end
+
+    def test_show_all_if_ambiguous_on
+      write_inputrc <<~LINES
+        set show-all-if-ambiguous on
+      LINES
+      start_terminal(20, 50, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl --complete}, startup_message: 'Multiline REPL.')
+      write("S\t")
+      close
+      assert_screen(<<~'EOC')
+        Multiline REPL.
+        prompt> S
+        ScriptError  String
+        Signal       SyntaxError
+      EOC
+    end
+
+    def test_show_all_if_ambiguous_on_and_menu_with_perfect_match
+      write_inputrc <<~LINES
+        set show-all-if-ambiguous on
+      LINES
+      start_terminal(20, 50, %W{ruby -I#{@pwd}/lib #{@pwd}/test/reline/yamatanooroti/multiline_repl --complete-menu-with-perfect-match}, startup_message: 'Multiline REPL.')
+      write("a\t")
+      close
+      assert_screen(<<~'EOC')
+        Multiline REPL.
+        prompt> abs
+        abs   abs2
+      EOC
+    end
+
     def test_simple_dialog
       iterate_over_face_configs do |config_name, config_file|
         start_terminal(20, 50, %W{ruby -I#{@pwd}/lib -r#{config_file.path} #{@pwd}/test/reline/yamatanooroti/multiline_repl --dialog simple}, startup_message: 'Multiline REPL.')