[ruby/irb] Page evaluation result's output

(https://github.com/ruby/irb/pull/784)

* Page evaluation result's output

This will make it easier to work with long output that exceeds the terminal's height.

* Use consistent TERM in rendering tests

This makes sure we get consistent result on all platforms.

https://github.com/ruby/irb/commit/4fedce93d3

2 files changed, 17 insertions, 14 deletions

diff --git a/lib/irb.rb b/lib/irb.rb
index 66149eb455..1ba335c087 100644
--- a/lib/irb.rb
+++ b/lib/irb.rb
@@ -20,6 +20,7 @@ require_relative "irb/color"
 require_relative "irb/version"
 require_relative "irb/easter-egg"
 require_relative "irb/debug"
+require_relative "irb/pager"
 
 # IRB stands for "interactive Ruby" and is a tool to interactively execute Ruby
 # expressions read from the standard input.
@@ -859,11 +860,12 @@ module IRB
           end
         end
       end
+
       if multiline_p && @context.newline_before_multiline_output?
-        printf @context.return_format, "\n#{str}"
-      else
-        printf @context.return_format, str
+        str = "\n" + str
       end
+
+      Pager.page_content(format(@context.return_format, str), retain_content: true)
     end
 
     # Outputs the local variables to this current session, including
diff --git a/lib/irb/pager.rb b/lib/irb/pager.rb
index e38d97e3c7..a0db5e93b4 100644
--- a/lib/irb/pager.rb
+++ b/lib/irb/pager.rb
@@ -7,9 +7,9 @@ module IRB
     PAGE_COMMANDS = [ENV['RI_PAGER'], ENV['PAGER'], 'less', 'more'].compact.uniq
 
     class << self
-      def page_content(content)
+      def page_content(content, **options)
         if content_exceeds_screen_height?(content)
-          page do |io|
+          page(**options) do |io|
             io.puts content
           end
         else
@@ -17,8 +17,8 @@ module IRB
         end
       end
 
-      def page
-        if IRB.conf[:USE_PAGER] && STDIN.tty? && pager = setup_pager
+      def page(retain_content: false)
+        if IRB.conf[:USE_PAGER] && STDIN.tty? && pager = setup_pager(retain_content: retain_content)
           begin
             pid = pager.pid
             yield pager
@@ -55,19 +55,20 @@ module IRB
           pageable_height * screen_width < Reline::Unicode.calculate_width(content, true)
       end
 
-      def setup_pager
+      def setup_pager(retain_content:)
         require 'shellwords'
 
-        PAGE_COMMANDS.each do |pager|
-          pager = Shellwords.split(pager)
-          next if pager.empty?
+        PAGE_COMMANDS.each do |pager_cmd|
+          cmd = Shellwords.split(pager_cmd)
+          next if cmd.empty?
 
-          if pager.first == 'less'
-            pager << '-R' unless pager.include?('-R')
+          if cmd.first == 'less'
+            cmd << '-R' unless cmd.include?('-R')
+            cmd << '-X' if retain_content && !cmd.include?('-X')
           end
 
           begin
-            io = IO.popen(pager, 'w')
+            io = IO.popen(cmd, 'w')
           rescue
             next
           end