[ruby/irb] Page ls's output (https://github.com/ruby/irb/pull/657)

* Page ls command's output

* Use Pager.page_content in show_cmds too

https://github.com/ruby/irb/commit/82d1687302

lib/irb/cmd/ls.rb

@@ -1,7 +1,9 @@
 # frozen_string_literal: true
 
 require "reline"
+require "stringio"
 require_relative "nop"
+require_relative "../pager"
 require_relative "../color"
 
 module IRB
@@ -33,7 +35,7 @@ module IRB
         o.dump("instance variables", obj.instance_variables)
         o.dump("class variables", klass.class_variables)
         o.dump("locals", locals)
-        nil
+        o.print_result
       end
 
       def dump_methods(o, klass, obj)
@@ -77,6 +79,11 @@ module IRB
         def initialize(grep: nil)
           @grep = grep
           @line_width = screen_width - MARGIN.length # right padding
+          @io = StringIO.new
+        end
+
+        def print_result
+          Pager.page_content(@io.string)
         end
 
         def dump(name, strs)
@@ -85,12 +92,12 @@ module IRB
           return if strs.empty?
 
           # Attempt a single line
-          print "#{Color.colorize(name, [:BOLD, :BLUE])}: "
+          @io.print "#{Color.colorize(name, [:BOLD, :BLUE])}: "
           if fits_on_line?(strs, cols: strs.size, offset: "#{name}: ".length)
-            puts strs.join(MARGIN)
+            @io.puts strs.join(MARGIN)
             return
           end
-          puts
+          @io.puts
 
           # Dump with the largest # of columns that fits on a line
           cols = strs.size
@@ -99,7 +106,7 @@ module IRB
           end
           widths = col_widths(strs, cols: cols)
           strs.each_slice(cols) do |ss|
-            puts ss.map.with_index { |s, i| "#{MARGIN}%-#{widths[i]}s" % s }.join
+            @io.puts ss.map.with_index { |s, i| "#{MARGIN}%-#{widths[i]}s" % s }.join
           end
         end
 

lib/irb/cmd/show_cmds.rb

@@ -29,9 +29,7 @@ module IRB
           output.puts
         end
 
-        Pager.page do |io|
+        Pager.page_content(output.string)
-          io.puts output.string
-        end
       end
     end
   end

lib/irb/pager.rb

@@ -7,6 +7,16 @@ module IRB
     PAGE_COMMANDS = [ENV['RI_PAGER'], ENV['PAGER'], 'less', 'more'].compact.uniq
 
     class << self
+      def page_content(content)
+        if content_exceeds_screen_height?(content)
+          page do |io|
+            io.puts content
+          end
+        else
+          $stdout.puts content
+        end
+      end
+
       def page
         if STDIN.tty? && pager = setup_pager
           begin
@@ -30,6 +40,21 @@ module IRB
 
       private
 
+      def content_exceeds_screen_height?(content)
+        screen_height, screen_width = begin
+          Reline.get_screen_size
+        rescue Errno::EINVAL
+          [24, 80]
+        end
+
+        pageable_height = screen_height - 3 # leave some space for previous and the current prompt
+
+        # If the content has more lines than the pageable height
+        content.lines.count > pageable_height ||
+          # Or if the content is a few long lines
+          pageable_height * screen_width < Reline::Unicode.calculate_width(content, true)
+      end
+
       def setup_pager
         require 'shellwords'
 

test/irb/test_cmd.rb

@@ -710,6 +710,16 @@ module TestIRB
   end
 
   class LsTest < CommandTestCase
+    def setup
+      STDIN.singleton_class.define_method :tty? do
+        false
+      end
+    end
+
+    def teardown
+      STDIN.singleton_class.remove_method :tty?
+    end
+
     def test_ls
       out, err = execute_lines(
         "class P\n",

test/irb/yamatanooroti/test_rendering.rb

@@ -270,6 +270,54 @@ class IRB::RenderingTest < Yamatanooroti::TestCase
     assert_match(/foobar/, screen)
   end
 
+  def test_pager_page_content_pages_output_when_it_does_not_fit_in_the_screen_because_of_total_length
+    write_irbrc <<~'LINES'
+      puts 'start IRB'
+      require "irb/pager"
+    LINES
+    start_terminal(10, 80, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
+    write("IRB::Pager.page_content('a' * (80 * 8))\n")
+    write("'foo' + 'bar'\n") # eval something to make sure IRB resumes
+    close
+
+    screen = result.join("\n").sub(/\n*\z/, "\n")
+    assert_match(/a{80}/, screen)
+    # because pager is invoked, foobar will not be evaluated
+    assert_not_match(/foobar/, screen)
+  end
+
+  def test_pager_page_content_pages_output_when_it_does_not_fit_in_the_screen_because_of_screen_height
+    write_irbrc <<~'LINES'
+      puts 'start IRB'
+      require "irb/pager"
+    LINES
+    start_terminal(10, 80, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
+    write("IRB::Pager.page_content('a\n' * 8)\n")
+    write("'foo' + 'bar'\n") # eval something to make sure IRB resumes
+    close
+
+    screen = result.join("\n").sub(/\n*\z/, "\n")
+    assert_match(/(a\n){8}/, screen)
+    # because pager is invoked, foobar will not be evaluated
+    assert_not_match(/foobar/, screen)
+  end
+
+  def test_pager_page_content_doesnt_page_output_when_it_fits_in_the_screen
+    write_irbrc <<~'LINES'
+      puts 'start IRB'
+      require "irb/pager"
+    LINES
+    start_terminal(10, 80, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
+    write("IRB::Pager.page_content('a' * (80 * 7))\n")
+    write("'foo' + 'bar'\n") # eval something to make sure IRB resumes
+    close
+
+    screen = result.join("\n").sub(/\n*\z/, "\n")
+    assert_match(/a{80}/, screen)
+    # because pager is not invoked, foobar will be evaluated
+    assert_match(/foobar/, screen)
+  end
+
   private
 
   def write_irbrc(content)