Avoid completing empty input (#832)

The candidate list for empty input is all methods + all variables + all constants + all keywords. It's a long list that is not useful.

Author: st0012

lib/irb/completion.rb

@@ -406,7 +406,13 @@ def retrieve_completion_data(input, bind:, doc_namespace:)
  else
  select_message(receiver, message, candidates.sort)
  end
-
+ when /^\s*$/
+ # empty input
+ if doc_namespace
+ nil
+ else
+ []
+ end
  else
  if doc_namespace
  vars = (bind.local_variables | bind.eval_instance_variables).collect{|m| m.to_s}

test/irb/test_completion.rb

@@ -204,6 +204,13 @@ def test_complete_constants
  end
  end
 
+ def test_not_completing_empty_string
+ assert_equal([], completion_candidates("", binding))
+ assert_equal([], completion_candidates(" ", binding))
+ assert_equal([], completion_candidates("\t", binding))
+ assert_equal(nil, doc_namespace("", binding))
+ end
+
  def test_complete_symbol
  symbols = %w"UTF-16LE UTF-7".map do |enc|
  "K".force_encoding(enc).to_sym

test/irb/yamatanooroti/test_rendering.rb

@@ -232,7 +232,8 @@ def test_autocomplete_with_showdoc_in_gaps_on_narrow_screen_right
  puts 'start IRB'
  LINES
  start_terminal(4, 19, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
- write("IR\C-i")
+ write("IR")
+ write("\C-i")
  close
 
  # This is because on macOS we display different shortcut for displaying the full doc
@@ -268,7 +269,8 @@ def test_autocomplete_with_showdoc_in_gaps_on_narrow_screen_left
  puts 'start IRB'
  LINES
  start_terminal(4, 12, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
- write("IR\C-i")
+ write("IR")
+ write("\C-i")
  close
  assert_screen(<<~EOC)
  start IRB