add EM::Synchrony.sync for inline fiber sync (aka, inlineCallbacks in

Python)

lib/em-synchrony.rb

@@ -24,4 +24,29 @@ def self.synchrony(blk=nil, tail=nil, &block)
     self.run(context, tail)
   end
 
-end
+  module Synchrony
+
+    # sync is a close relative to inclineCallbacks from Twisted (Python)
+    #
+    # Synchrony.sync allows you to write sequential code while using asynchronous
+    # or callback-based methods under the hood. Example:
+    #
+    # result = EM::Synchrony.sync EventMachine::HttpRequest.new(URL).get
+    # p result.response
+    #
+    # As long as the asynchronous function returns a Deferrable object, which
+    # has a "callback" and an "errback", the sync methond will automatically
+    # yield and automatically resume your code (via Fibers) when the call
+    # either succeeds or fails. You do not need to patch or modify the
+    # Deferrable object, simply pass it to EM::Synchrony.sync
+    #
+    def self.sync(df)
+      f = Fiber.current
+      df.callback { |r| f.resume(r) }
+      df.errback { |r| f.resume(r) }
+
+      Fiber.yield
+    end
+  end
+
+end

spec/inlinesync_spec.rb

@@ -0,0 +1,37 @@
+require "spec/helper/all"
+require "em-synchrony/iterator"
+
+describe EventMachine::Synchrony do
+
+  URL = "http://localhost:8081/"
+  DELAY = 0.01
+
+  it "should allow inline callbacks for Deferrable object" do
+    EM.synchrony do
+      s = StubServer.new("HTTP/1.0 200 OK\r\nConnection: close\r\n\r\nFoo", DELAY)
+
+      result = EM::Synchrony.sync EventMachine::HttpRequest.new(URL).aget
+      result.response.should match(/Foo/)
+
+      EM.stop
+    end
+  end
+
+  it "should inline errback/callback cases" do
+    EM.synchrony do
+      class E
+        include EventMachine::Deferrable
+        def run
+          EM.add_timer(0.01) {fail("uh oh!")}
+          self
+        end
+      end
+
+      result = EM::Synchrony.sync E.new.run
+      result.should match(/uh oh!/)
+
+      EM.stop
+    end
+  end
+
+end