don't diff single line strings

Closes #5.

Rakefile

@@ -71,6 +71,7 @@ Rake::RDocTask.new do |rdoc|
 end
 
 task :clobber do
+  rm_rf 'doc'
   rm_rf 'pkg'
   rm_rf 'tmp'
   rm_rf 'coverage'

lib/rspec/expectations/differ.rb

@@ -19,8 +19,9 @@ def diff_as_string(data_new, data_old)
         file_length_difference = 0
         diffs.each do |piece|
           begin
-            hunk = Diff::LCS::Hunk.new(data_old, data_new, piece, context_lines,
-                                       file_length_difference)
+            hunk = Diff::LCS::Hunk.new(
+              data_old, data_new, piece, context_lines, file_length_difference
+            )
             file_length_difference = hunk.file_length_difference      
             next unless oldhunk      
             # Hunks may overlap, which is why we need to be careful when our
@@ -44,7 +45,8 @@ def diff_as_object(target,expected)
         diff_as_string(PP.pp(target,""), PP.pp(expected,""))
       end
 
-      protected
+    protected
+
       def format
         :unified
       end

lib/rspec/expectations/fail_with.rb

@@ -8,21 +8,39 @@ def differ
       # raises a RSpec::Expectations::ExpectationNotMetError with message
       #
       # When a differ has been assigned and fail_with is passed
-      # <code>expected</code> and <code>target</code>, passes them
+      # <code>expected</code> and <code>actual</code>, passes them
       # to the differ to append a diff message to the failure message.
-      def fail_with(message, expected=nil, target=nil) # :nodoc:
-        if message.nil?
+      def fail_with(message, expected=nil, actual=nil) # :nodoc:
+        if !message
           raise ArgumentError, "Failure message is nil. Does your matcher define the " +
                                "appropriate failure_message_for_* method to return a string?"
         end
-        unless (differ.nil? || expected.nil? || target.nil?)
-          if expected.is_a?(String)
-            message << "\nDiff:" << self.differ.diff_as_string(target.to_s, expected)
-          elsif !target.is_a?(Proc)
-            message << "\nDiff:" << self.differ.diff_as_object(target, expected)
+
+        if actual && expected
+          if all_strings?(actual, expected)
+            if any_multiline_strings?(actual, expected)
+              message << "\nDiff:" << self.differ.diff_as_string(actual, expected)
+            end
+          elsif no_procs?(actual, expected)
+            message << "\nDiff:" << self.differ.diff_as_object(actual, expected)
           end
         end
-        Kernel::raise(RSpec::Expectations::ExpectationNotMetError.new(message))
+
+        raise(RSpec::Expectations::ExpectationNotMetError.new(message))
+      end
+
+    private
+
+      def no_procs?(*args)
+        args.none? {|a| Proc === a}
+      end
+
+      def all_strings?(*args)
+        args.all? {|a| String === a}
+      end
+
+      def any_multiline_strings?(*args)
+        all_strings?(*args) && args.any? {|a| a =~ /\n/}
       end
     end
   end

rspec-expectations.gemspec

@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
 
   s.required_rubygems_version = Gem::Requirement.new("> 1.3.1") if s.respond_to? :required_rubygems_version=
   s.authors = ["David Chelimsky", "Chad Humphries"]
-  s.date = %q{2010-06-08}
+  s.date = %q{2010-06-13}
   s.description = %q{rspec expectations (should[_not] and matchers)}
   s.email = %q{dchelimsky@gmail.com;chad.humphries@gmail.com}
   s.extra_rdoc_files = [

spec/rspec/expectations/fail_with_spec.rb

@@ -1,34 +1,40 @@
 require 'spec_helper'
 
 describe RSpec::Expectations, "#fail_with with diff" do
+  let(:differ) { double("differ") }
+
   before(:each) do
-    @differ = mock("differ")
-    RSpec::Expectations.stub(:differ) { @differ }
+    RSpec::Expectations.stub(:differ) { differ }
   end
 
-  it "should not call differ if no expected/actual" do
+  it "does not call differ if no expected/actual" do
     lambda {
       RSpec::Expectations.fail_with "the message"
     }.should fail_with("the message")
   end
 
-  it "should call differ if expected/actual are presented separately" do
-    @differ.should_receive(:diff_as_string).and_return("diff")
+  it "calls differ if expected/actual are presented separately" do
+    differ.should_receive(:diff_as_string).and_return("diff")
     lambda {
-      RSpec::Expectations.fail_with "the message", "expected", "actual"
+      RSpec::Expectations.fail_with "the message", "expected\nthis", "actual"
     }.should fail_with("the message\nDiff:diff")
   end
 
-  it "should call differ if expected/actual are not strings" do
-    @differ.should_receive(:diff_as_object).and_return("diff")
+  it "does not call differ if expected/actual are single line strings" do
+    differ.should_not_receive(:diff_as_string)
+    RSpec::Expectations.fail_with ("the message", "expected", "actual") rescue nil
+  end
+
+  it "calls differ if expected/actual are not strings" do
+    differ.should_receive(:diff_as_object).and_return("diff")
     lambda {
-      RSpec::Expectations.fail_with "the message", :expected, :actual
+      RSpec::Expectations.fail_with "the message", Object.new, Object.new
     }.should fail_with("the message\nDiff:diff")
   end
 
-  it "should not call differ if expected or actual are procs" do
-    @differ.should_not_receive(:diff_as_string)
-    @differ.should_not_receive(:diff_as_object)
+  it "does not call differ if expected or actual are procs" do
+    differ.should_not_receive(:diff_as_string)
+    differ.should_not_receive(:diff_as_object)
     lambda {
       RSpec::Expectations.fail_with "the message", lambda {}, lambda {}
     }.should fail_with("the message")