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

NEWS

@@ -158,6 +158,9 @@ with all sufficient information, see the ChangeLog file or Redmine
   * IPAddr now rejects invalid address mask. [Bug #13399]
   * IPAddr#ipv4_compat and #ipv4_compat? are deprecated. [Bug #13769]
 
+* IRB
+  * Show source around `binding.irb` on session start
+
 * Net::HTTP
   * Add more HTTP status classes
 

lib/irb.rb

@@ -706,6 +706,8 @@ class Binding
   undef irb if method_defined?(:irb)
   def irb
     IRB.setup(eval("__FILE__"))
-    IRB::Irb.new(IRB::WorkSpace.new(self)).run(IRB.conf)
+    workspace = IRB::WorkSpace.new(self)
+    STDOUT.print(workspace.code_around_binding)
+    IRB::Irb.new(workspace).run(IRB.conf)
   end
 end

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

test/irb/test_workspace.rb

@@ -0,0 +1,78 @@
+# frozen_string_literal: false
+require 'test/unit'
+require 'tempfile'
+require 'irb/workspace'
+
+module TestIRB
+  class TestWorkSpace < Test::Unit::TestCase
+    def test_code_around_bindinig
+      Tempfile.create do |f|
+        code = <<~RUBY
+          # 1
+          # 2
+          IRB::WorkSpace.new(binding) # 3
+          # 4
+          # 5
+        RUBY
+        f.print(code)
+        f.close
+
+        workspace = eval(code, binding, f.path)
+        assert_equal(<<~EOS, workspace.code_around_binding)
+
+          From: #{f.path} @ line 3 :
+
+              1: # 1
+              2: # 2
+           => 3: IRB::WorkSpace.new(binding) # 3
+              4: # 4
+              5: # 5
+
+        EOS
+      end
+    end
+
+    def test_code_around_bindinig_with_script_lines__
+      with_script_lines do |script_lines|
+        Tempfile.create do |f|
+          code = "IRB::WorkSpace.new(binding)\n"
+          script_lines[f.path] = code
+
+          workspace = eval(code, binding, f.path)
+          assert_equal(<<~EOS, workspace.code_around_binding)
+
+            From: #{f.path} @ line 1 :
+
+             => 1: IRB::WorkSpace.new(binding)
+
+          EOS
+        end
+      end
+    end
+
+    def test_code_around_bindinig_on_irb
+      workspace = eval("IRB::WorkSpace.new(binding)", binding, "(irb)")
+      assert_equal(nil, workspace.code_around_binding)
+    end
+
+    private
+
+    def with_script_lines
+      script_lines = nil
+      debug_lines = {}
+      Object.class_eval do
+        if defined?(SCRIPT_LINES__)
+          script_lines = SCRIPT_LINES__
+          remove_const :SCRIPT_LINES__
+        end
+        const_set(:SCRIPT_LINES__, debug_lines)
+      end
+      yield debug_lines
+    ensure
+      Object.class_eval do
+        remove_const :SCRIPT_LINES__
+        const_set(:SCRIPT_LINES__, script_lines) if script_lines
+      end
+    end
+  end
+end