Add support for diffing ActiveRecord objects

Introduce a new way of using the gem in Rails projects. Instead of
saying:

    require "super_diff/rspec"

you say:

    require "super_diff/rspec-rails"

And this will give you support for ActiveRecord (and other Rails types
of things in the future). Or you can say:

    require "super_diff/rspec"
    require "super_diff/active_record"

if you're only interested in support for ActiveRecord.

Author: mcmire

Gemfile

@@ -4,7 +4,9 @@ source "https://rubygems.org"
 
 git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
 
+gem "activerecord-jdbcsqlite3-adapter", platform: :jruby
 gem "childprocess"
+gem "jdbc-sqlite3", platform: :jruby
 gem "pry-byebug", platform: :mri
 gem "pry-nav", platform: :jruby
 gem "rake"
@@ -13,5 +15,6 @@ gem "rspec-expectations", github: "rspec/rspec-expectations"
 gem "rspec-mocks", github: "rspec/rspec-mocks"
 gem "rspec-support", github: "rspec/rspec-support"
 gem "rubocop"
+gem "sqlite3", platform: [:ruby, :mswin, :mingw]
 
 gemspec

README.md

@@ -101,7 +101,7 @@ gem "super_diff"
 After running `bundle install`, add the following to your `rails_helper`:
 
 ``` ruby
-require "super_diff/rspec"
+require "super_diff/rspec-rails"
 ```
 
 You're done!

lib/super_diff/active_record.rb

@@ -0,0 +1,22 @@
+module SuperDiff
+  module ActiveRecord
+    autoload(
+      :ObjectInspection,
+      "super_diff/active_record/object_inspection",
+    )
+    autoload(
+      :OperationalSequencer,
+      "super_diff/active_record/operational_sequencer",
+    )
+  end
+end
+
+if defined?(SuperDiff::RSpec)
+  SuperDiff::RSpec.configuration.add_extra_operational_sequencer_class(
+    SuperDiff::ActiveRecord::OperationalSequencer,
+  )
+end
+
+SuperDiff::ObjectInspection.map.prepend(
+  SuperDiff::ActiveRecord::ObjectInspection::MapExtension,
+)

lib/super_diff/active_record/object_inspection.rb

@@ -0,0 +1,14 @@
+module SuperDiff
+  module ActiveRecord
+    module ObjectInspection
+      autoload(
+        :Inspector,
+        "super_diff/active_record/object_inspection/inspector",
+      )
+      autoload(
+        :MapExtension,
+        "super_diff/active_record/object_inspection/map_extension",
+      )
+    end
+  end
+end

lib/super_diff/active_record/object_inspection/inspector.rb

@@ -0,0 +1,36 @@
+module SuperDiff
+  module ActiveRecord
+    module ObjectInspection
+      Inspector = SuperDiff::ObjectInspection::InspectionTree.new do
+        add_text do |object|
+          "#<#{object.class} "
+        end
+
+        when_multiline do
+          add_text "{"
+        end
+
+        nested do |object|
+          add_break
+
+          insert_separated_list(
+            ["id"] + (object.attributes.keys.sort - ["id"]),
+            separator: ",",
+          ) do |name|
+            add_text name
+            add_text ": "
+            add_inspection_of object.read_attribute(name)
+          end
+        end
+
+        add_break
+
+        when_multiline do
+          add_text "}"
+        end
+
+        add_text ">"
+      end
+    end
+  end
+end

lib/super_diff/active_record/object_inspection/map_extension.rb

@@ -0,0 +1,15 @@
+module SuperDiff
+  module ActiveRecord
+    module ObjectInspection
+      module MapExtension
+        def call(object)
+          if object.is_a?(::ActiveRecord::Base)
+            Inspector
+          else
+            super
+          end
+        end
+      end
+    end
+  end
+end

lib/super_diff/active_record/operational_sequencer.rb

@@ -0,0 +1,29 @@
+module SuperDiff
+  module ActiveRecord
+    class OperationalSequencer < SuperDiff::OperationalSequencers::Object
+      def self.applies_to?(expected, actual)
+        expected.is_a?(::ActiveRecord::Base) &&
+          actual.is_a?(::ActiveRecord::Base) &&
+          expected.class == actual.class
+      end
+
+      protected
+
+      def attribute_names
+        ["id"] + (expected.attributes.keys.sort - ["id"])
+      end
+
+      private
+
+      def establish_expected_and_actual_attributes
+        @expected_attributes = attribute_names.reduce({}) do |hash, name|
+          hash.merge(name => expected.read_attribute(name))
+        end
+
+        @actual_attributes = attribute_names.reduce({}) do |hash, name|
+          hash.merge(name => actual.read_attribute(name))
+        end
+      end
+    end
+  end
+end

lib/super_diff/object_inspection.rb

@@ -1,25 +1,22 @@
 module SuperDiff
   module ObjectInspection
     autoload :InspectionTree, "super_diff/object_inspection/inspection_tree"
-    autoload(
-      :InspectorFinder,
-      "super_diff/object_inspection/inspector_finder",
-    )
     autoload :Inspectors, "super_diff/object_inspection/inspectors"
+    autoload :Map, "super_diff/object_inspection/map"
     autoload :Nodes, "super_diff/object_inspection/nodes"
 
     class << self
-      attr_accessor :inspector_finder
+      attr_accessor :map
     end
 
     def self.inspect(object, as_single_line:, indent_level: 0)
-      inspector_finder.call(object).evaluate(
+      map.call(object).evaluate(
         object,
         as_single_line: as_single_line,
         indent_level: indent_level,
       )
     end
 
-    self.inspector_finder = InspectorFinder
+    self.map = Map.new
   end
 end

lib/super_diff/object_inspection/inspector_finder.rb renamed to lib/super_diff/object_inspection/map.rb

@@ -1,7 +1,11 @@
 module SuperDiff
   module ObjectInspection
-    class InspectorFinder
-      def self.call(object)
+    class Map
+      def prepend(mod)
+        singleton_class.prepend(mod)
+      end
+
+      def call(object)
         if object.respond_to?(:attributes_for_super_diff)
           Inspectors::CustomObject
         else
@@ -13,8 +17,7 @@ def self.call(object)
           when String
             Inspectors::String
           when true, false, nil, Symbol, Numeric, Regexp
-            Inspectors::Primitive
-          else
+            Inspectors::Primitive else
             Inspectors::DefaultObject
           end
         end

lib/super_diff/rails.rb

@@ -0,0 +1 @@
+require "super_diff/active_record"