Introduce Dry::Core::Inspect

.gitignore

@@ -8,4 +8,5 @@
 /spec/reports/
 /tmp/
 spec/examples.txt
-
+.ruby-version
+.ruby-gemset

lib/dry/core/inspect.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module Dry
+  module Core
+    class Inspect < ::Module
+      def initialize(*attributes, **value_methods_map)
+        super()
+
+        define_inspect_methods(attributes.flatten(1), **value_methods_map)
+      end
+
+      private
+
+      def define_inspect_methods(attributes, **value_methods_map)
+        define_inspect_method(attributes, **value_methods_map)
+        define_pretty_print(attributes, **value_methods_map)
+      end
+
+      def define_inspect_method(attributes, **value_methods_map)
+        define_method(:inspect) do
+          instance_inspect = if self.class.name
+                               "#<#{self.class.name}"
+                             else
+                               Kernel.instance_method(:to_s).bind(self).call.chomp!(">")
+                             end
+
+          inspect = attributes.map { |name|
+            "#{name}=#{__send__(value_methods_map[name] || name).inspect}"
+          }.join(", ")
+          "#{instance_inspect} #{inspect}>"
+        end
+      end
+
+      def define_pretty_print(attributes, **value_methods_map)
+        define_method(:pretty_print) do |pp|
+          object_group_method = self.class.name ? :object_group : :object_address_group
+          pp.public_send(object_group_method, self) do
+            pp.seplist(attributes, -> { pp.text "," }) do |name|
+              pp.breakable " "
+              pp.group(1) do
+                pp.text name.to_s
+                pp.text "="
+                pp.pp __send__(value_methods_map[name] || name)
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/dry/core/inspect_spec.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require "pp"
+
+RSpec.describe Dry::Core::Inspect do
+  subject(:inspect) { Dry::Core::Inspect.new(:fullname, :secret_question_answer, **value_methods_map) }
+
+  let(:value_methods_map) { {} }
+  let(:klass) do
+    Class.new do
+      attr_reader :fullname, :secret_question_answer
+      private :fullname, :secret_question_answer
+
+      def initialize(fullname, secret_question_answer)
+        @fullname = fullname
+        @secret_question_answer = secret_question_answer
+      end
+
+      private
+
+      def secret_question_answer_encrypted
+        @secret_question_answer * 42
+      end
+    end
+  end
+  let(:instance) { klass.new("John Doe", 42) }
+
+  before { klass.include(inspect) }
+
+  it "defines a pretty_print method" do
+    expect(instance.pretty_inspect)
+      .to match(/\A#<#<Class:0x[a-f0-9]{16}>:0x[a-f0-9]{16}\n fullname="John Doe",\n secret_question_answer=42>\n\z/)
+  end
+
+  it "defines an inspect method" do
+    expect(instance.inspect)
+      .to match(/\A#<#<Class:0x[a-f0-9]{16}>:0x[a-f0-9]{16} fullname="John Doe", secret_question_answer=42>\z/)
+  end
+
+  context "with a non-anonymous class" do
+    before { stub_const("User", klass) }
+
+    it "uses the class name in the pretty_inspect output" do
+      expect(instance.pretty_inspect).to eq("#<User fullname=\"John Doe\", secret_question_answer=42>\n")
+    end
+
+    it "uses the class name in the inspect output" do
+      expect(instance.inspect).to eq("#<User fullname=\"John Doe\", secret_question_answer=42>")
+    end
+  end
+
+  context "with a value method given" do
+    let(:value_methods_map) { {secret_question_answer: :secret_question_answer_encrypted} }
+
+    it "uses the value method in the pretty_inspect output" do
+      expect(instance.pretty_inspect)
+        .to match(/\A#<#<Class:0x[a-f0-9]{16}>:0x[a-f0-9]{16}\n fullname="John Doe",\n secret_question_answer=1764>\n\z/)
+    end
+
+    it "uses the value method in the inspect output" do
+      expect(instance.inspect)
+        .to match(/\A#<#<Class:0x[a-f0-9]{16}>:0x[a-f0-9]{16} fullname="John Doe", secret_question_answer=1764>\z/)
+    end
+  end
+end