Fix Dry::Core::Equalizer() usage (#79)

## Fix Dry::Core::Equalizer() usage

Provide a `Dry::Core.Equalizer` method that builds the module when called as `include Dry::Core::Equalizer()` as documented. Previously, this method did not exist at all, so _only_ usages of the "legacy" `Dry.Equalizer` method would work. With this change, we can now appropriately expect `Dry::Core.Equalizer` to be the mainstream usage.

To ensure this, update the specs to expect `Dry::Core::Equalizer()` to be used by default, and provide a single spec to ensure that the legacy `Dry::Equalizer()` method continues to work.

Also update specs to remove direct requires of `dry/core/equalizer`, since a require of `dry/core` alone should be sufficient to load Equalizer when it is used, given we use Zeitwerk.

## Remove all cherry-picked requires from specs and docs

While we're here, make the equivalent change of removing cherry-picked requires from all our other modules, both in specs and docs. These are no longer needed since we use Zeitwerk. A simple `require "dry/core"` alone is enough.

docsite/source/cache.html.md

@@ -7,7 +7,7 @@ name: dry-core
 Allows you to cache call results that are solely determined by arguments.
 
 ```ruby
-require 'dry/core/cache'
+require "dry/core"
 
 class Foo
   extend Dry::Core::Cache

docsite/source/deprecations.html.md

@@ -7,7 +7,7 @@ name: dry-core
 To deprecate ruby methods you need to extend the `Dry::Core::Deprecations` module with a tag that will be displayed in the output. For example:
 
 ```ruby
-require 'dry/core/deprecations'
+require "dry/core"
 
 class Foo
   extend Dry::Core::Deprecations[:tag]

docsite/source/equalizer.html.md

@@ -9,7 +9,7 @@ A simple mixin that can be used to add instance variable based equality, equival
 ### Usage
 
 ```ruby
-require 'dry/core/equalizer'
+require "dry/core"
 
 class GeoLocation
   include Dry::Core::Equalizer(:latitude, :longitude)

docsite/source/extensions.html.md

@@ -7,7 +7,7 @@ name: dry-core
 Define extensions that can be later enabled by the user.
 
 ```ruby
-require 'dry/core/extensions'
+require "dry/core"
 
 class Foo
   extend Dry::Core::Extensions

lib/dry/core.rb

@@ -27,6 +27,17 @@ def self.loader
     end
 
     loader.setup
+
+    # Build an equalizer module for the inclusion in other class
+    #
+    # ## Credits
+    #
+    # Equalizer has been originally imported from the equalizer gem created by Dan Kubb
+    #
+    # @api public
+    def self.Equalizer(*keys, **options)
+      Equalizer.new(*keys, **options)
+    end
   end
 
   # See dry/core/equalizer.rb

spec/dry/core/basic_object_spec.rb

@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/basic_object"
-require "pp"
-
 class ExternalTestClass
 end
 
@@ -78,6 +75,7 @@ def respond_to?(_method_name, _include_all = false) # rubocop:disable Style/Opti
 
     # See https://github.com/hanami/utils/issues/234
     it "outputs the inspection to the given printer" do
+      require "pp" # rubucop:disable Lint/RedundantRequireStatement
       printer = PP.new
       subject = TestClass.new
       subject.pretty_print(printer)

spec/dry/core/cache_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/cache"
-
 RSpec.describe Dry::Core::Cache do
   shared_examples_for "class with cache" do
     describe "#fetch_or_store" do

spec/dry/core/class_attributes_spec.rb

@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/class_attributes"
 require "dry-types"
 
 RSpec.describe "Class Macros" do

spec/dry/core/class_builder_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/class_builder"
-
 RSpec.describe Dry::Core::ClassBuilder do
   subject(:builder) { described_class.new(**options) }
 

spec/dry/core/constants_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/constants"
-
 RSpec.describe Dry::Core::Constants do
   before do
     class ClassWithConstants

spec/dry/core/deprecations_spec.rb

@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/deprecations"
 require "tempfile"
 
 RSpec.describe Dry::Core::Deprecations do

spec/dry/core/descendants_tracker_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/descendants_tracker"
-
 RSpec.describe Dry::Core::DescendantsTracker do
   before do
     module Test

spec/dry/core/equalizer/included_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "spec_helper"
-require "dry/core/equalizer"
 
 RSpec.describe Dry::Core::Equalizer, "#included" do
   subject { descendant.instance_exec(object) { |mod| include mod } }
@@ -33,7 +32,7 @@
 
     superclass.class_eval do
       define_method(:included) do |_|
-        # Only set the flag when an Dry::Equalizer instance is included.
+        # Only set the flag when an Dry::Core::Equalizer instance is included.
         # Otherwise, other module includes (which get triggered internally
         # in RSpec when `change` is used for the first time, since it uses
         # autoloading for its matchers) will wrongly set this flag.

spec/dry/core/equalizer/legacy_name_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+RSpec.describe "legacy Dry::Equalizer name" do
+  it "behaves the same as when using Dry::Core::Equalizer" do
+    klass = Class.new {
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+      end
+    }
+    allow(klass).to receive_messages(name: nil, inspect: "User") # specify the class #inspect method
+    klass.include Dry::Equalizer(:name)
+
+    instance = klass.new("Jane")
+    other = instance.dup
+
+    expect(instance).to eql(other)
+  end
+end

spec/dry/core/equalizer/methods/eql_predicate_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "spec_helper"
-require "dry/core/equalizer"
 
 RSpec.describe Dry::Core::Equalizer::Methods, "#eql?" do
   subject { object.eql?(other) }

spec/dry/core/equalizer/methods/equality_operator_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "spec_helper"
-require "dry/core/equalizer"
 
 RSpec.describe Dry::Core::Equalizer::Methods, "#==" do
   subject { object == other }

spec/dry/core/equalizer/universal_spec.rb

@@ -1,14 +1,13 @@
 # frozen_string_literal: true
 
 require "spec_helper"
-require "dry/core/equalizer"
 
 RSpec.describe Dry::Core::Equalizer do
   let(:name)   { "User"          }
   let(:klass)  { ::Class.new     }
 
   context "with no keys" do
-    subject { Dry::Equalizer() }
+    subject { Dry::Core::Equalizer() }
 
     before do
       # specify the class #name method
@@ -73,7 +72,7 @@
   end
 
   context "with keys" do
-    subject { Dry::Equalizer(*keys) }
+    subject { Dry::Core::Equalizer(*keys) }
 
     let(:keys)       { %i[firstname lastname].freeze  }
     let(:firstname)  { "John"                         }
@@ -158,7 +157,7 @@ def initialize(firstname, lastname)
 
     context "when immutable" do
       describe "#hash" do
-        subject { Dry::Equalizer(*keys, immutable: true) }
+        subject { Dry::Core::Equalizer(*keys, immutable: true) }
 
         it "returns memoized hash" do
           expect { instance.firstname = "Changed" }.not_to(change { instance.hash })
@@ -177,7 +176,7 @@ def initialize(firstname, lastname)
   end
 
   context "with duplicate keys" do
-    subject { Dry::Equalizer(*keys) }
+    subject { Dry::Core::Equalizer(*keys) }
 
     let(:keys)       { %i[firstname firstname lastname].freeze  }
     let(:firstname)  { "John"                                   }
@@ -216,7 +215,7 @@ def initialize(firstname, lastname)
 
   context "with options" do
     context "w/o inspect" do
-      subject { Dry::Equalizer(*keys, inspect: false) }
+      subject { Dry::Core::Equalizer(*keys, inspect: false) }
 
       let(:keys)       { %i[firstname lastname].freeze  }
       let(:firstname)  { "John"                         }

spec/dry/core/extensions_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/extensions"
-
 RSpec.describe Dry::Core::Extensions do
   subject do
     Class.new do

spec/dry/core/inflector_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "dry/core/inflector"
-
 RSpec.describe Dry::Core::Inflector do
   shared_examples "an inflector" do
     it "singularises" do

spec/dry/core/memoizable_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "concurrent/atomic/atomic_fixnum"
-require "dry/core/memoizable"
 require "tempfile"
 require_relative "../../support/memoized"