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

lib/super_diff/rspec/differ.rb

@@ -0,0 +1,119 @@
+RSpec::Expectations.instance_eval do
+  def differ
+    SuperDiff::RSpec::Differ
+  end
+end
+
+RSpec::Core::Formatters::ConsoleCodes.instance_eval do
+  # UPDATE: Patch so it returns nothing if code_or_symbol is nil
+  def console_code_for(code_or_symbol)
+    if code_or_symbol
+      if (config_method = config_colors_to_methods[code_or_symbol])
+        console_code_for RSpec.configuration.__send__(config_method)
+      elsif RSpec::Core::Formatters::ConsoleCodes::VT100_CODE_VALUES.key?(code_or_symbol)
+        code_or_symbol
+      else
+        RSpec::Core::Formatters::ConsoleCodes::VT100_CODES.fetch(code_or_symbol) do
+          console_code_for(:white)
+        end
+      end
+    end
+  end
+
+  # UPDATE: Patch so it does not apply a color if code_or_symbol is nil
+  def wrap(text, code_or_symbol)
+    if RSpec.configuration.color_enabled? && code = console_code_for(code_or_symbol)
+      "\e[#{code}m#{text}\e[0m"
+    else
+      text
+    end
+  end
+end
+
+RSpec::Core::Formatters::ExceptionPresenter.class_eval do
+  # UPDATE: Copy from SyntaxHighlighter::CodeRayImplementation
+  RESET_CODE = "\e[0m"
+
+  def initialize(exception, example, options={})
+    @exception               = exception
+    @example                 = example
+    # UPDATE: Use no color by default
+    @message_color           = options[:message_color]
+    @description             = options.fetch(:description)            { example.full_description }
+    @detail_formatter        = options.fetch(:detail_formatter)       { Proc.new {} }
+    @extra_detail_formatter  = options.fetch(:extra_detail_formatter) { Proc.new {} }
+    @backtrace_formatter     = options.fetch(:backtrace_formatter)    { RSpec.configuration.backtrace_formatter }
+    @indentation             = options.fetch(:indentation, 2)
+    @skip_shared_group_trace = options.fetch(:skip_shared_group_trace, false)
+    @failure_lines           = options[:failure_lines]
+  end
+
+  def add_shared_group_lines(lines, colorizer)
+    return lines if @skip_shared_group_trace
+
+    example.metadata[:shared_group_inclusion_backtrace].each do |frame|
+      # Update: Use red instead of the default color
+      lines << colorizer.wrap(frame.description, :failure)
+    end
+
+    lines
+  end
+
+  # UPDATE: Style the first part in blue and the snippet of the line that failed
+  # in white
+  def failure_slash_error_lines
+    lines = read_failed_lines
+
+    failure_slash_error = RSpec::Core::Formatters::ConsoleCodes.wrap(
+      "Failure/Error: ",
+      :detail
+    )
+
+    if lines.count == 1
+      lines[0] =
+        failure_slash_error +
+        RSpec::Core::Formatters::ConsoleCodes.wrap(lines[0].strip, :white)
+    else
+      least_indentation = SnippetExtractor.least_indentation_from(lines)
+      lines = lines.map do |line|
+        RSpec::Core::Formatters::ConsoleCodes.wrap(
+          line.sub(/^#{least_indentation}/, '  '),
+          :white
+        )
+      end
+      lines.unshift(failure_slash_error)
+    end
+
+    lines
+  end
+end
+
+RSpec::Matchers::BuiltIn::Eq.class_eval do
+  def failure_message
+    "\n" +
+      colorizer.wrap("expected: #{expected_formatted}\n", :failure) +
+      colorizer.wrap("     got: #{actual_formatted}\n\n", :success) +
+      colorizer.wrap("(compared using ==)\n", :detail)
+  end
+
+  def failure_message_when_negated
+    "\n" +
+      colorizer.wrap("expected: value != #{expected_formatted}\n", :failure) +
+      colorizer.wrap("     got: #{actual_formatted}\n\n", :success) +
+      colorizer.wrap("(compared using ==)\n", :detail)
+  end
+
+  private
+
+  def colorizer
+    RSpec::Core::Formatters::ConsoleCodes
+  end
+end
+
+RSpec::Core::Formatters::SyntaxHighlighter.class_eval do
+  private
+
+  def implementation
+    RSpec::Core::Formatters::SyntaxHighlighter::NoSyntaxHighlightingImplementation
+  end
+end