make dsl work with raw rack apps and also rack web frameworks

lib/rack/stream/dsl.rb

@@ -2,7 +2,7 @@
 
 module Rack
   class Stream
-    # DSL to access Rack::Stream::App methods
+    # DSL to access Rack::Stream::App methods.
     #
     # ## Example
     # ```ruby
@@ -23,15 +23,35 @@ class Stream
     #
     # run App.new
     # ```
+    #
+    # ## Rack Frameworks
+    #
+    # If you mix this module into a class that already responds to `#call`,
+    # then you need to make `env` available so that methods can be delegated to
+    # `env['rack.stream']`. There is no need to declare a `stream` block in this case.
+    #
+    # For example, Sinatra makes `env` available to its endpoints:
+    #
+    # ```ruby
+    # class App < Sinatra::Base
+    #   include Rack::Stream::DSL
+    #
+    #   get '/' do
+    #     chunk "Hello"  # no need to declare stream block b/c `env` is available
+    #   end
+    # end
+    # ```
     module DSL
       def self.included(base)
         base.extend ClassMethods
         base.extend Forwardable
 
         base.class_eval do
-          include InstanceMethods
+          unless base.respond_to? :call
+            include InstanceMethods
+            attr_reader :env
+          end
 
-          attr_reader :env
           def_delegators :"env['rack.stream']", :after_open, :before_chunk, :chunk, :after_chunk, :before_close, :close, :after_close, :stream_transport
         end
       end

spec/lib/rack/stream/dsl_spec.rb

@@ -9,33 +9,55 @@
     EM.stop  # TODO: would prefer to have only stream_spec require em
   end
 
-  context '#call' do
-    it 'should declare #call' do
-      subject.respond_to?(:call).should be_true
+  context 'raw rack' do
+    context '#call' do
+      it 'should declare #call' do
+        subject.respond_to?(:call).should be_true
+      end
+
+      it 'should raise error if no run block is defined' do
+        expect {
+          subject.call(mock)
+        }.to raise_error(Rack::Stream::DSL::StreamBlockNotDefined)
+      end
     end
 
-    it 'should raise error if no run block is defined' do
-      expect {
+    context '.run' do
+      subject do
+        Class.new {
+          include Rack::Stream::DSL
+
+          attr_reader :run_called
+          stream do
+            @run_called = true
+          end
+        }.new
+      end
+
+      it 'should eval run block for new requests' do
         subject.call(mock)
-      }.to raise_error(Rack::Stream::DSL::StreamBlockNotDefined)
+        subject.run_called.should be_true
+      end
     end
   end
 
-  context '.run' do
+  context 'rack framework' do
     subject do
       Class.new {
-        include Rack::Stream::DSL
-
-        attr_reader :run_called
-        stream do
-          @run_called = true
+        # mock of a rack web framework that already knows call
+        def call(env)
         end
+
+        include Rack::Stream::DSL
       }.new
     end
 
-    it 'should eval run block for new requests' do
-      subject.call(mock)
-      subject.run_called.should be_true
+    context '#call' do
+      it 'should raise error if no run block is defined' do
+        expect {
+          subject.call(mock)
+        }.to_not raise_error(Rack::Stream::DSL::StreamBlockNotDefined)
+      end
     end
   end
 end