Add integration with RSpec

Right now, RSpec doesn't support replacing its differ with a custom
implementation. Therefore, we have to resort to monkey-patching some
internal RSpec classes to use SuperDiff instead. While we're at it,
disable some of the coloring that RSpec does, particularly its habit of
styling failures in blood red. We want to be able to show off the diff
and all of its glory and this just gets in the way.

Author: mcmire

.gitignore

@@ -1,2 +1,3 @@
 .DS_Store
 spec/examples.txt
+tmp

lib/super_diff.rb

@@ -43,8 +43,9 @@
 
 require_relative "super_diff/differs/base"
 require_relative "super_diff/differs/array"
+require_relative "super_diff/differs/empty"
 require_relative "super_diff/differs/hash"
-require_relative "super_diff/differs/string"
+require_relative "super_diff/differs/multi_line_string"
 require_relative "super_diff/differs/object"
 require_relative "super_diff/differs"
 require_relative "super_diff/differ"

lib/super_diff/differ.rb

@@ -7,7 +7,7 @@ def self.call(*args)
     def initialize(
       expected,
       actual,
-      indent_level:,
+      indent_level: 0,
       index_in_collection: nil,
       extra_classes: [],
       extra_operational_sequencer_classes: [],
@@ -35,6 +35,10 @@ def call
 
     private
 
+    attr_reader :expected, :actual, :indent_level, :index_in_collection,
+      :extra_classes, :extra_operational_sequencer_classes,
+      :extra_diff_formatter_classes
+
     def resolved_class
       (Differs::DEFAULTS + extra_classes).detect do |klass|
         klass.applies_to?(expected) && klass.applies_to?(actual)

lib/super_diff/differs.rb

@@ -1,5 +1,5 @@
 module SuperDiff
   module Differs
-    DEFAULTS = [Array, Hash, String, Object]
+    DEFAULTS = [Array, Hash, MultiLineString, Object, Empty]
   end
 end

lib/super_diff/differs/empty.rb

@@ -0,0 +1,13 @@
+module SuperDiff
+  module Differs
+    class Empty < Base
+      def self.applies_to?(value)
+        true
+      end
+
+      def call
+        ""
+      end
+    end
+  end
+end

lib/super_diff/differs/multi_line_string.rb

@@ -0,0 +1,27 @@
+module SuperDiff
+  module Differs
+    class MultiLineString < Base
+      def self.applies_to?(value)
+        value.is_a?(::String) && value.include?("\n")
+      end
+
+      def call
+        DiffFormatters::MultiLineString.call(
+          operations,
+          indent_level: indent_level
+        )
+      end
+
+      private
+
+      def operations
+        OperationalSequencers::MultiLineString.call(
+          expected: expected,
+          actual: actual,
+          extra_operational_sequencer_classes: extra_operational_sequencer_classes,
+          extra_diff_formatter_classes: extra_diff_formatter_classes
+        )
+      end
+    end
+  end
+end

lib/super_diff/differs/string.rb

@@ -31,13 +31,12 @@ def fail
       private
 
       def diff
-        DiffFormatters::MultiLineString.call(operations, indent_level: 0)
-      end
-
-      def operations
-        OperationalSequencers::MultiLineString.call(
-          expected: expected,
-          actual: actual
+        Differs::MultiLineString.call(
+          expected,
+          actual,
+          indent_level: 0,
+          extra_operational_sequencer_classes: extra_operational_sequencer_classes,
+          extra_diff_formatter_classes: extra_diff_formatter_classes
         )
       end
     end

lib/super_diff/equality_matchers/multi_line_string.rb

@@ -0,0 +1,19 @@
+require_relative "../super_diff"
+require_relative "rspec/differ"
+require_relative "rspec/monkey_patches"
+
+module SuperDiff
+  module RSpec
+    class << self
+      attr_accessor :extra_operational_sequencer_classes
+      attr_accessor :extra_diff_formatter_classes
+
+      def configure
+        yield self
+      end
+    end
+
+    self.extra_operational_sequencer_classes = []
+    self.extra_diff_formatter_classes = []
+  end
+end

lib/super_diff/rspec.rb

@@ -0,0 +1,15 @@
+module SuperDiff
+  module RSpec
+    module Differ
+      def self.diff(actual, expected)
+        diff = SuperDiff::Differ.call(
+          expected,
+          actual,
+          extra_operational_sequencer_classes: RSpec.extra_operational_sequencer_classes,
+          extra_diff_formatter_classes: RSpec.extra_diff_formatter_classes
+        )
+        "\n\n" + diff
+      end
+    end
+  end
+end