irb.rb: show source around binding.irb on start

[Feature #14124] [ruby-dev:50319] [close GH-1764]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60888 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/irb/workspace.rb b/lib/irb/workspace.rb
index 9051f96df0..5c1e97a981 100644
--- a/lib/irb/workspace.rb
+++ b/lib/irb/workspace.rb
@@ -107,6 +107,27 @@ EOF
       bt
     end
 
+    def code_around_binding
+      file = @binding.eval('__FILE__')
+      pos  = @binding.eval('__LINE__') - 1
+      return nil unless File.exist?(file)
+
+      if defined?(SCRIPT_LINES__) && SCRIPT_LINES__.key?(file)
+        lines = SCRIPT_LINES__[file].split(/^/)
+      else
+        lines = File.readlines(file)
+      end
+
+      start_pos = [pos - 5, 0].max
+      end_pos   = [pos + 5, lines.size - 1].min
+
+      body = (start_pos..end_pos).map do |current_pos|
+        lineno = "%#{end_pos.to_s.length}d" % (current_pos + 1)
+        " #{pos == current_pos ? '=>' : '  '} #{lineno}: #{lines[current_pos]}"
+      end.join
+      "\nFrom: #{file} @ line #{pos + 1} :\n\n#{body}\n"
+    end
+
     def IRB.delete_caller
     end
   end