From 99525cb6ffee2dadf4b11ce1a8094a353ef1a566 Mon Sep 17 00:00:00 2001
From: Diego Toral <diegotoral@gmail.com>
Date: Tue, 20 Jul 2021 10:36:58 -0300
Subject: [PATCH] ActiveSupport::Configurable default value option

Sometimes it can be very strange or long have to define default values
for config accessors as blocks, specially when config is a simple value
like 1, true, :symbol. This commit adds the ability to specify those
values by just passing a ` default` option when defining the accessor.

It also makes config accessor's interface similar to other Rails
methods like `class_attribute`, which also has the instance_reader,
instance_writer and instance_accessor options.
---
 activesupport/lib/active_support/configurable.rb |  9 ++++++---
 activesupport/test/configurable_test.rb          | 11 ++++++++++-
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/activesupport/lib/active_support/configurable.rb b/activesupport/lib/active_support/configurable.rb
index 92bd411df5..a6ae8b3494 100644
--- a/activesupport/lib/active_support/configurable.rb
+++ b/activesupport/lib/active_support/configurable.rb
@@ -94,17 +94,19 @@ module ActiveSupport
       #   User.new.allowed_access = true # => NoMethodError
       #   User.new.allowed_access        # => NoMethodError
       #
-      # Also you can pass a block to set up the attribute with a default value.
+      # Also you can pass <tt>default</tt> or a block to set up the attribute with a default value.
       #
       #   class User
       #     include ActiveSupport::Configurable
+      #     config_accessor :allowed_access, default: false
       #     config_accessor :hair_colors do
       #       [:brown, :black, :blonde, :red]
       #     end
       #   end
       #
+      #   User.allowed_access # => false
       #   User.hair_colors # => [:brown, :black, :blonde, :red]
-      def config_accessor(*names, instance_reader: true, instance_writer: true, instance_accessor: true) # :doc:
+      def config_accessor(*names, instance_reader: true, instance_writer: true, instance_accessor: true, default: nil) # :doc:
         names.each do |name|
           raise NameError.new("invalid config attribute name") unless /\A[_A-Za-z]\w*\z/.match?(name)
 
@@ -118,7 +120,8 @@ module ActiveSupport
             class_eval reader, __FILE__, reader_line if instance_reader
             class_eval writer, __FILE__, writer_line if instance_writer
           end
-          send("#{name}=", yield) if block_given?
+
+          send("#{name}=", block_given? ? yield : default)
         end
       end
       private :config_accessor
diff --git a/activesupport/test/configurable_test.rb b/activesupport/test/configurable_test.rb
index a466a1d11d..b41e05c7b2 100644
--- a/activesupport/test/configurable_test.rb
+++ b/activesupport/test/configurable_test.rb
@@ -50,7 +50,7 @@ class ConfigurableActiveSupport < ActiveSupport::TestCase
     assert_not_respond_to instance, :baz=
   end
 
-  test "configuration accessors can take a default value" do
+  test "configuration accessors can take a default value as a block" do
     parent = Class.new do
       include ActiveSupport::Configurable
       config_accessor :hair_colors, :tshirt_colors do
@@ -62,6 +62,15 @@ class ConfigurableActiveSupport < ActiveSupport::TestCase
     assert_equal [:black, :blue, :white], parent.tshirt_colors
   end
 
+  test "configuration accessors can take a default value as an option" do
+    parent = Class.new do
+      include ActiveSupport::Configurable
+      config_accessor :foo, default: :bar
+    end
+
+    assert_equal :bar, parent.foo
+  end
+
   test "configuration hash is available on instance" do
     instance = Parent.new
     assert_equal :bar, instance.config.foo