Fix spec type inferrence.

- In #970 we added `infer_spec_type_from_file_location!` but forgot
  to remove the code in `lib/rspec/rails/configuration.rb` that
  made it always infer - so the opt-in API was there but it
  was always enabled. Here I've made it truly opt-in.
- The logic of `infer_spec_type_from_file_location!` also setup
  the helper module inclusion via explicit `:type` metadata but
  was only intended to setup the implicit mapping of spec file
  location to type.  Here I've made the module inclusion via
  `:type` always work w/o an explicit config option needed to
  enable it.
- We used to mutate the `:type` metadata on inclusion of the helper
  module, but this caused bugs such as #825. The problem is that
  rspec-core uses a raw hash for the metadata and doesn't re-apply
  filtering/inclusion logic when the metadata hash is mutated.
  Instead, we use a new explicit `define_derived_metadata` API.

Fixes #825 and closes #829.

features/directory_structure.feature

@@ -24,6 +24,12 @@ Feature: Directory Structure
       """ruby
       require "spec_helper"
 
+      RSpec.configure do |config|
+        config.before(:context, :type => :controller) do
+          puts "Running a controller example group"
+        end
+      end
+
       describe WidgetsController do
         it "responds successfully" do
           get :index
@@ -33,12 +39,19 @@ Feature: Directory Structure
       """
     When I run `rspec spec`
     Then the example should pass
+     And the output should contain "Running a controller example group"
 
   Scenario: Specs in other directories must have their types specified manually
     Given a file named "spec/functional/widgets_controller_spec.rb" with:
       """ruby
       require "spec_helper"
 
+      RSpec.configure do |config|
+        config.before(:context, :type => :controller) do
+          puts "Running a controller example group"
+        end
+      end
+
       describe WidgetsController, :type => :controller do
         it "responds successfully" do
           get :index
@@ -48,6 +61,7 @@ Feature: Directory Structure
       """
     When I run `rspec spec`
     Then the example should pass
+     And the output should contain "Running a controller example group"
 
   Scenario: Specs in canonical directories can override their types
     Given a file named "spec/routing/duckduck_routing_spec.rb" with:

lib/rspec/rails.rb

@@ -1,2 +1,45 @@
-require 'rspec/rails/without_filetype_infer'
-require 'rspec/rails/configuration'
+require 'rspec/core'
+require 'rspec/collection_matchers'
+require 'rails/version'
+require 'rspec/rails/extensions'
+require 'rspec/rails/view_rendering'
+require 'rspec/rails/adapters'
+require 'rspec/rails/matchers'
+require 'rspec/rails/fixture_support'
+require 'rspec/rails/example'
+require 'rspec/rails/vendor/capybara'
+
+RSpec.configure do |c|
+  c.backtrace_exclusion_patterns << /vendor\//
+  c.backtrace_exclusion_patterns << /lib\/rspec\/rails/
+
+  c.include RSpec::Rails::ControllerExampleGroup, :type => :controller
+  c.include RSpec::Rails::HelperExampleGroup,     :type => :helper
+  c.include RSpec::Rails::ModelExampleGroup,      :type => :model
+  c.include RSpec::Rails::RequestExampleGroup,    :type => :request
+  c.include RSpec::Rails::RoutingExampleGroup,    :type => :routing
+  c.include RSpec::Rails::ViewExampleGroup,       :type => :view
+  c.include RSpec::Rails::FeatureExampleGroup,    :type => :feature
+
+  if defined?(RSpec::Rails::MailerExampleGroup)
+    c.include RSpec::Rails::MailerExampleGroup, :type => :mailer
+  end
+
+  def c.infer_spec_type_from_file_location!
+    {
+      :controller => %w[spec controllers],
+      :helper     => %w[spec helpers],
+      :mailer     => %w[spec mailers],
+      :model      => %w[spec models],
+      :request    => %w[spec (requests|integration|api)],
+      :routing    => %w[spec routing],
+      :view       => %w[spec views],
+      :feature    => %w[spec features]
+    }.each do |type, dir_parts|
+      escaped_path = Regexp.compile(dir_parts.join('[\\\/]') + '[\\\/]')
+      define_derived_metadata(:file_path => escaped_path) do |metadata|
+        metadata[:type] ||= type
+      end
+    end
+  end
+end

lib/rspec/rails/example.rb

@@ -7,5 +7,3 @@
 require 'rspec/rails/example/routing_example_group'
 require 'rspec/rails/example/model_example_group'
 require 'rspec/rails/example/feature_example_group'
-
-require 'rspec/rails/infer_type_configuration'

lib/rspec/rails/example/controller_example_group.rb

@@ -155,8 +155,6 @@ def method_missing(method, *args, &block)
     included do
       subject { controller }
 
-      metadata[:type] = :controller
-
       before do
         self.routes = ::Rails.application.routes
       end

lib/rspec/rails/example/feature_example_group.rb

@@ -6,8 +6,6 @@ module FeatureExampleGroup
     DEFAULT_HOST = "www.example.com"
 
     included do
-      metadata[:type] = :feature
-
       app = ::Rails.application
       if app.respond_to?(:routes)
         include app.routes.url_helpers     if app.routes.respond_to?(:url_helpers)

lib/rspec/rails/example/helper_example_group.rb

@@ -30,8 +30,6 @@ def _controller_path(example)
     end
 
     included do
-      metadata[:type] = :helper
-
       before do |example|
         controller.controller_path = _controller_path(example)
       end

lib/rspec/rails/example/mailer_example_group.rb

@@ -6,7 +6,6 @@ module MailerExampleGroup
       include ActionMailer::TestCase::Behavior
 
       included do
-        metadata[:type] = :mailer
         include ::Rails.application.routes.url_helpers
         options = ::Rails.configuration.action_mailer.default_url_options
         options.each { |key, value| default_url_options[key] = value } if options

lib/rspec/rails/example/model_example_group.rb

@@ -2,9 +2,5 @@ module RSpec::Rails
   module ModelExampleGroup
     extend ActiveSupport::Concern
     include RSpec::Rails::RailsExampleGroup
-
-    included do
-      metadata[:type] = :model
-    end
   end
 end

lib/rspec/rails/example/request_example_group.rb

@@ -13,8 +13,6 @@ def app
     end
 
     included do
-      metadata[:type] = :request
-
       before do
         @routes = ::Rails.application.routes
       end

lib/rspec/rails/example/routing_example_group.rb

@@ -30,8 +30,6 @@ def routes(&blk)
     end
 
     included do
-      metadata[:type] = :routing
-
       before do
         self.routes = ::Rails.application.routes
       end

lib/rspec/rails/example/view_example_group.rb

@@ -142,7 +142,6 @@ def _include_controller_helpers
     included do
       include ExampleMethods
 
-      metadata[:type] = :view
       helper(*_default_helpers)
 
       before do

spec/rspec/rails/example/controller_example_group_spec.rb

@@ -6,8 +6,8 @@ def self.abstract?; false; end
 
 module RSpec::Rails
   describe ControllerExampleGroup do
-    it { is_expected.to be_included_in_files_in('./spec/controllers/') }
-    it { is_expected.to be_included_in_files_in('.\\spec\\controllers\\') }
+    it { is_expected.to be_included_in_files_in('./spec/controllers/').or_tagged_with_type(:controller) }
+    it { is_expected.to be_included_in_files_in('.\\spec\\controllers\\').or_tagged_with_type(:controller) }
 
     let(:group) do
       RSpec::Core::ExampleGroup.describe do
@@ -19,10 +19,6 @@ module RSpec::Rails
       expect(group.included_modules).to include(RSpec::Rails::Matchers::RoutingMatchers)
     end
 
-    it "adds :type => :controller to the metadata" do
-      expect(group.metadata[:type]).to eq(:controller)
-    end
-
     context "with implicit subject" do
       it "uses the controller as the subject" do
         controller = double('controller')

spec/rspec/rails/example/feature_example_group_spec.rb

@@ -2,16 +2,8 @@
 
 module RSpec::Rails
   describe FeatureExampleGroup do
-    it { is_expected.to be_included_in_files_in('./spec/features/') }
-    it { is_expected.to be_included_in_files_in('.\\spec\\features\\') }
-
-    it "adds :type => :feature to the metadata" do
-      group = RSpec::Core::ExampleGroup.describe do
-        include FeatureExampleGroup
-      end
-
-      expect(group.metadata[:type]).to eq(:feature)
-    end
+    it { is_expected.to be_included_in_files_in('./spec/features/').or_tagged_with_type(:feature) }
+    it { is_expected.to be_included_in_files_in('.\\spec\\features\\').or_tagged_with_type(:feature) }
 
     it "includes Rails route helpers" do
       with_isolated_stderr do

spec/rspec/rails/example/helper_example_group_spec.rb

@@ -5,8 +5,8 @@ module RSpec::Rails
     module ::FoosHelper; end
     subject { HelperExampleGroup }
 
-    it { is_expected.to be_included_in_files_in('./spec/helpers/') }
-    it { is_expected.to be_included_in_files_in('.\\spec\\helpers\\') }
+    it { is_expected.to be_included_in_files_in('./spec/helpers/').or_tagged_with_type(:helper) }
+    it { is_expected.to be_included_in_files_in('.\\spec\\helpers\\').or_tagged_with_type(:helper) }
 
     it "provides a controller_path based on the helper module's name" do
       example = double
@@ -16,13 +16,6 @@ module ::FoosHelper; end
       expect(helper_spec.__send__(:_controller_path, example)).to eq("foos")
     end
 
-    it "adds :type => :helper to the metadata" do
-      group = RSpec::Core::ExampleGroup.describe do
-        include HelperExampleGroup
-      end
-      expect(group.metadata[:type]).to eq(:helper)
-    end
-
     describe "#helper" do
       it "returns the instance of AV::Base provided by AV::TC::Behavior" do
         helper_spec = Object.new.extend HelperExampleGroup