Delegate model generator description to orm hooked generator

Use orm hooked generator description for model generator help.

railties/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Delegate model generator description to orm hooked generator.
+
+    *Gannon McGibbon*
+
 *   Execute `rails runner` scripts inside the executor.
 
     Enables error reporting, query cache, etc.

railties/lib/rails/generators/base.rb

@@ -189,6 +189,13 @@ module Rails
             class_option(name, defaults.merge!(options))
           end
 
+          klass = self
+
+          singleton_class.define_method("#{name}_generator") do
+            value = class_options[name].default
+            Rails::Generators.find_by_namespace(klass.generator_name, value)
+          end
+
           hooks[name] = [ in_base, as_hook ]
           invoke_from_option(name, options, &block)
         end

railties/lib/rails/generators/rails/model/model_generator.rb

@@ -9,6 +9,10 @@ module Rails
 
       argument :attributes, type: :array, default: [], banner: "field[:type][:index] field[:type][:index]"
       hook_for :orm, required: true, desc: "ORM to be invoked"
+
+      class << self
+        delegate(:desc, to: :orm_generator)
+      end
     end
   end
 end

railties/lib/rails/generators/rails/resource/resource_generator.rb

@@ -16,6 +16,12 @@ module Rails
                              desc: "Actions for the resource controller"
 
       hook_for :resource_route, required: true
+
+      class << self
+        def desc(description = nil)
+          ERB.new(File.read(usage_path)).result(binding)
+        end
+      end
     end
   end
 end

railties/test/generators/orm_test.rb

@@ -2,6 +2,7 @@
 
 require "generators/generators_test_helper"
 require "rails/generators/rails/scaffold_controller/scaffold_controller_generator"
+require "rails/generators/rails/model/model_generator"
 
 # Mock out two ORMs
 module ORMWithGenerators
@@ -17,7 +18,7 @@ module ORMWithoutGenerators
   # No generators
 end
 
-class OrmTest < Rails::Generators::TestCase
+class ScaffoldOrmTest < Rails::Generators::TestCase
   include GeneratorsTestHelper
   tests Rails::Generators::ScaffoldControllerGenerator
 
@@ -38,3 +39,38 @@ class OrmTest < Rails::Generators::TestCase
     assert_equal "foo", orm_instance.name
   end
 end
+
+module TestOrmWithDescription
+  module Generators
+    class ModelGenerator < Rails::Generators::ModelGenerator
+      def self.usage_path
+        true
+      end
+
+      def self.desc
+        "My description"
+      end
+    end
+  end
+end
+
+class ModelOrmTest < ActiveSupport::TestCase
+  def test_active_record_description_is_used_by_default
+    assert_match(/Description:.*/, Rails::Generators::ModelGenerator.desc)
+  end
+
+  def test_orm_description_is_used_when_configured
+    with_configured(:orm, :test_orm_with_description) do
+      assert_equal("My description", Rails::Generators::ModelGenerator.desc)
+    end
+  end
+
+  private
+    def with_configured(hook, value)
+      previous_default = Rails::Generators::ModelGenerator.class_options[hook].default
+      Rails::Generators::ModelGenerator.class_options[hook].instance_variable_set(:@default, value)
+      yield
+    ensure
+      Rails::Generators::ModelGenerator.class_options[hook].instance_variable_set(:@default, previous_default)
+    end
+end

railties/test/generators/resource_generator_test.rb

@@ -13,6 +13,11 @@ class ResourceGeneratorTest < Rails::Generators::TestCase
     Rails::Generators::ModelHelpers.skip_warn = false
   end
 
+  def test_help_with_usage_description
+    content = run_generator ["--help"]
+    assert_match(/Generates a new resource/, content)
+  end
+
   def test_help_with_inherited_options
     content = run_generator ["--help"]
     assert_match(/ActiveRecord options:/, content)