Avoid unnecessary defined? usage on Ruby 3+ when using the :ensure op…

…tion

defined? was used previously because before Ruby 3, accessing a
undefined instance variable resulted in a verbose mode warning.
As of Ruby 3, it no longer does, so there is no reason to use
defined?.  This results in fewer VM instructions, so this will
improve performance, though the difference is unlikely to be
measurable.

CHANGELOG

@@ -1,3 +1,7 @@
+=== master
+
+* Avoid unnecessary defined? usage on Ruby 3+ when using the :ensure option (jeremyevans)
+
 === 1.10.0 (2020-11-13)
 
 * Improve template parsing, mostly by reducing allocations (jeremyevans)

lib/erubi.rb

@@ -14,6 +14,7 @@ module Erubi
 
   TEXT_END = RUBY_VERSION >= '2.1' ? "'.freeze;" : "';"
   MATCH_METHOD = RUBY_VERSION >= '2.4' ? :match? : :match
+  SKIP_DEFINED_FOR_INSTANCE_VARIABLE = RUBY_VERSION > '3'
   # :nocov:
 
   begin
@@ -87,7 +88,14 @@ def initialize(input, properties={})
 
       @src = src = properties[:src] || String.new
       src << "# frozen_string_literal: true\n" if properties[:freeze]
-      src << "begin; __original_outvar = #{bufvar} if defined?(#{bufvar}); " if properties[:ensure]
+      if properties[:ensure]
+        src << "begin; __original_outvar = #{bufvar}"
+        if SKIP_DEFINED_FOR_INSTANCE_VARIABLE && /\A@[^@]/ =~ bufvar
+          src << "; "
+        else
+          src << " if defined?(#{bufvar}); "
+        end
+      end
 
       unless @escapefunc = properties[:escapefunc]
         if escape

test/test.rb

@@ -261,7 +261,7 @@ def self.quux
 </table>
 <%== i+1 %>
 END1
-begin; __original_outvar = @a if defined?(@a); @a = ::String.new; @a << '<table>
+begin; __original_outvar = @a#{' if defined?(@a)' if RUBY_VERSION < '3'}; @a = ::String.new; @a << '<table>
  <tbody>
 ';   i = 0
      list.each_with_index do |item, i| 
@@ -292,6 +292,53 @@ def self.quux
     @a.must_equal 'bar'
   end
 
+  it "should handle ensure option with no bufvar" do
+    list = list = ['&\'<>"2']
+    @options[:ensure] = true
+    check_output(<<END1, <<END2, <<END3){}
+<table>
+ <tbody>
+  <% i = 0
+     list.each_with_index do |item, i| %>
+  <tr>
+   <td><%= i+1 %></td>
+   <td><%== item %></td>
+  </tr>
+ <% end %>
+ </tbody>
+</table>
+<%== i+1 %>
+END1
+begin; __original_outvar = _buf if defined?(_buf); _buf = ::String.new; _buf << '<table>
+ <tbody>
+';   i = 0
+     list.each_with_index do |item, i| 
+ _buf << '  <tr>
+   <td>'; _buf << ( i+1 ).to_s; _buf << '</td>
+   <td>'; _buf << ::Erubi.h(( item )); _buf << '</td>
+  </tr>
+';  end 
+ _buf << ' </tbody>
+</table>
+'; _buf << ::Erubi.h(( i+1 )); _buf << '
+';
+_buf.to_s
+; ensure
+  _buf = __original_outvar
+end
+END2
+<table>
+ <tbody>
+  <tr>
+   <td>1</td>
+   <td>&amp;&#39;&lt;&gt;&quot;2</td>
+  </tr>
+ </tbody>
+</table>
+1
+END3
+  end
+
   it "should handle trailing rspace with - modifier in <%|= and <%|" do
     eval(::Erubi::CaptureEndEngine.new("<%|= '&' -%>\n<%| -%>\n").src).must_equal '&'
   end