Add :locals option for erb. General approach and some of the code was borrowed from rails (compilable.rb)

lib/sinatra.rb

@@ -576,9 +576,19 @@ module Sinatra
     private 
     
       def render_erb(content, options = {})
-        ::ERB.new(content).result(binding)
+        locals_opt = options.delete(:locals) || {}
+
+        locals_code = ""
+        locals_hash = {} 
+        locals_opt.each do |key, value|
+          locals_code << "#{key} = locals_hash[:#{key}]\n"
+          locals_hash[:"#{key}"] = value
+        end
+ 
+        body = ::ERB.new(content).src
+        eval("#{locals_code}#{body}", binding)
       end
-      
+
   end
 
   module Haml

test/erb_test.rb

@@ -23,6 +23,26 @@ context "Erb" do
       body.should == '2'
 
     end
+
+    specify "should take an options hash with :locals set with a string" do
+      get '/locals' do
+        erb '<%= foo %>', :locals => {:foo => "Bar"}
+      end
+
+      get_it '/locals'
+      should.be.ok
+      body.should == 'Bar'
+    end
+
+    specify "should take an options hash with :locals set with a complex object" do
+      get '/locals-complex' do
+        erb '<%= foo[0] %>', :locals => {:foo => ["foo", "bar", "baz"]}
+      end
+
+      get_it '/locals-complex'
+      should.be.ok
+      body.should == 'foo'
+    end
   end
   
   context "with layouts" do