Start adding support for the on_body handler

lib/fake_web/ext/curb_patch.rb

@@ -34,7 +34,7 @@ def initialize(url = nil, &block)
       def perform_with_fakeweb
         if FakeWeb.registered_uri?(:get, url)
           r = FakeWeb::Registry.instance.curl_response_for(:get, url)
-          self.body_str = r.body_str
+          __process_body(r.body_str)
           true
         elsif FakeWeb.allow_net_connect?
           perform_without_fakeweb
@@ -46,6 +46,27 @@ def perform_with_fakeweb
       alias_method :perform_without_fakeweb, :perform
       alias_method :perform, :perform_with_fakeweb
 
+
+      # TODO: shouldn't really be adding new methods. Put this somewhere else?
+      def __process_body(body)
+        # TODO: lock around this so another thread doesn't see the momentarily-nil proc?
+        body_handler = self.on_body
+        self.on_body(&body_handler) unless body_handler.nil?
+
+        if body_handler.nil?
+          self.body_str = body
+        else
+          self.body_str = nil
+          handler_return_value = body_handler.call(body)
+          if !handler_return_value.is_a?(Integer)
+            FakeWeb::Utility.rb_warn "Curl data handlers should return the number of bytes read as an Integer", caller[1]
+          elsif handler_return_value != body.length
+            # NOTE: Curb docs claim this should be an AbortedByCallbackError, but it raises a WriteError
+            raise Curl::Err::WriteError, "Failed writing received data to disk/application"
+          end
+        end
+      end
+
     end
   end
 end

lib/fake_web/utility.rb

@@ -28,6 +28,12 @@ def self.uri_escape(*args)
       end
     end
 
+    # Emulate rb_warn in pure ruby
+    def self.rb_warn(msg, caller_line = caller[0])
+      file_and_line = caller_line.sub(/:in .+$/, '')
+      warn "#{file_and_line}: warning: #{msg}"
+    end
+
     def self.puts_warning_for_net_http_around_advice_libs_if_needed
       libs = {"Samuel" => defined?(Samuel)}
       warnings = libs.select { |_, loaded| loaded }.map do |name, _|

test/test_curb.rb

@@ -15,10 +15,10 @@ def test_curl_easy_class_perform_with_different_body
   end
 
   def test_curl_easy_instance_perform
-    FakeWeb.register_uri(:get, "http://example.com", :body => "example3")
+    FakeWeb.register_uri(:get, "http://example.com", :body => "example")
     curl = Curl::Easy.new("http://example.com")
     assert_equal true, curl.perform
-    assert_equal "example3", curl.body_str
+    assert_equal "example", curl.body_str
   end
 
   def test_easy_class_perform_with_unregistered_uri_raises
@@ -34,5 +34,42 @@ def test_easy_instance_perform_with_unregistered_uri_raises
     end
   end
 
+  def test_body_handler_is_used
+    FakeWeb.register_uri(:get, "http://example.com", :body => "example")
+    curl = Curl::Easy.new("http://example.com")
+    body = ""
+    curl.on_body { |data| body << data; data.length }
+    curl.perform
+    assert_equal "example", body
+    assert_nil curl.body_str
+  end
+
+  def test_body_handler_is_preserved
+    FakeWeb.register_uri(:get, "http://example.com", :body => "example")
+    curl = Curl::Easy.new("http://example.com")
+    body = ""
+    curl.on_body { |data| body << data; data.length }
+    curl.perform
+    assert_equal "example", body
+    body = ""
+    curl.perform
+    assert_equal "example", body
+  end
+
+  def test_perform_raises_when_body_handler_returns_wrong_number
+    FakeWeb.register_uri(:get, "http://example.com", :body => "example")
+    curl = Curl::Easy.new("http://example.com")
+    curl.on_body { |data| 0 }
+    exception = assert_raise(Curl::Err::WriteError) { curl.perform }
+    assert_equal "Failed writing received data to disk/application", exception.message
+  end
+
+  def test_perform_raises_when_body_handler_returns_non_number
+    FakeWeb.register_uri(:get, "http://example.com", :body => "example")
+    curl = Curl::Easy.new("http://example.com")
+    curl.on_body { |data| data }
+    warning, line = capture_stderr { curl.perform }, __LINE__
+    assert warning.include? "test_curb.rb:#{line}: warning: Curl data handlers should return the number of bytes read as an Integer\n"
+  end
 
 end