Introduce Middleware DEFAULT_OPTIONS with Application and Instance Configurability

docs/middleware/index.md

@@ -114,6 +114,49 @@ conn = Faraday.new do |f|
 end
 ```
 
+### DEFAULT_OPTIONS
+
+`DEFAULT_OPTIONS` improve the flexibility and customizability of new and existing middleware. Class-level `DEFAULT_OPTIONS` and the ability to set these defaults at the application level compliment existing functionality in which options can be passed into middleware on a per-instance basis.
+
+#### Using DEFAULT_OPTIONS
+
+Using `RaiseError` as an example, you can see that `DEFAULT_OPTIONS` have been defined at the top of the class:
+
+```ruby
+  DEFAULT_OPTIONS = { include_request: true }.freeze
+```
+
+These options will be set at the class level upon instantiation and referenced as needed within the class. From our same example:
+
+```ruby
+  def response_values(env)
+  ...
+    return response unless options[:include_request]
+  ...
+```
+
+If the default value provides the desired functionality, no further consideration is needed.
+
+#### Setting Alternative Options per Application
+
+In the case where it is desirable to change the default option for all instances within an application, it can be done by configuring the options in a `/config/initializers` file. For example:
+
+```ruby
+# config/initializers/faraday_config.rb
+
+Faraday::Response::RaiseError.default_options = { include_request: false }
+```
+
+After app initialization, all instances of the middleware will have the newly configured option(s). They can still be overriden on a per-instance bases (if handled in the middleware), like this:
+
+```ruby
+  Faraday.new do |f|
+    ...
+    f.response :raise_error, include_request: true 
+    ...
+  end
+```
+
 ### Available Middleware
 
 The following pages provide detailed configuration for the middleware that ships with Faraday:

lib/faraday/error.rb

@@ -158,4 +158,8 @@ class SSLError < Error
   # Raised by middlewares that parse the response, like the JSON response middleware.
   class ParsingError < Error
   end
+
+  # Raised by Faraday::Middleware and subclasses when invalid default_options are used
+  class InitializationError < Error
+  end
 end

lib/faraday/middleware.rb

@@ -1,15 +1,57 @@
 # frozen_string_literal: true
 
+require 'monitor'
+
 module Faraday
   # Middleware is the basic base class of any Faraday middleware.
   class Middleware
     extend MiddlewareRegistry
 
     attr_reader :app, :options
 
+    DEFAULT_OPTIONS = {}.freeze
+
     def initialize(app = nil, options = {})
       @app = app
-      @options = options
+      @options = self.class.default_options.merge(options)
+    end
+
+    class << self
+      # Faraday::Middleware::default_options= allows user to set default options at the Faraday::Middleware
+      # class level.
+      #
+      # @example Set the Faraday::Response::RaiseError option, `include_request` to `false`
+      # my_app/config/initializers/my_faraday_middleware.rb
+      #
+      # Faraday::Response::RaiseError.default_options = { include_request: false }
+      #
+      def default_options=(options = {})
+        validate_default_options(options)
+        lock.synchronize do
+          @default_options = default_options.merge(options)
+        end
+      end
+
+      # default_options attr_reader that initializes class instance variable
+      # with the values of any Faraday::Middleware defaults, and merges with
+      # subclass defaults
+      def default_options
+        @default_options ||= DEFAULT_OPTIONS.merge(self::DEFAULT_OPTIONS)
+      end
+
+      private
+
+      def lock
+        @lock ||= Monitor.new
+      end
+
+      def validate_default_options(options)
+        invalid_keys = options.keys.reject { |opt| self::DEFAULT_OPTIONS.key?(opt) }
+        return unless invalid_keys.any?
+
+        raise(Faraday::InitializationError,
+              "Invalid options provided. Keys not found in #{self}::DEFAULT_OPTIONS: #{invalid_keys.join(', ')}")
+      end
     end
 
     def call(env)

lib/faraday/response/raise_error.rb

@@ -10,6 +10,8 @@ class RaiseError < Middleware
       ServerErrorStatuses = (500...600)
       # rubocop:enable Naming/ConstantName
 
+      DEFAULT_OPTIONS = { include_request: true }.freeze
+
       def on_complete(env)
         case env[:status]
         when 400
@@ -58,7 +60,7 @@ def response_values(env)
 
         # Include the request data by default. If the middleware was explicitly
         # configured to _not_ include request data, then omit it.
-        return response unless options.fetch(:include_request, true)
+        return response unless options[:include_request]
 
         response.merge(
           request: {

spec/faraday/middleware_spec.rb

@@ -67,4 +67,147 @@ def on_error(error)
       end
     end
   end
+
+  describe '::default_options' do
+    let(:subclass_no_options) { FaradayMiddlewareSubclasses::SubclassNoOptions }
+    let(:subclass_one_option) { FaradayMiddlewareSubclasses::SubclassOneOption }
+    let(:subclass_two_options) { FaradayMiddlewareSubclasses::SubclassTwoOptions }
+
+    def build_conn(resp_middleware)
+      Faraday.new do |c|
+        c.adapter :test do |stub|
+          stub.get('/success') { [200, {}, 'ok'] }
+        end
+        c.response resp_middleware
+      end
+    end
+
+    RSpec.shared_context 'reset @default_options' do
+      before(:each) do
+        FaradayMiddlewareSubclasses::SubclassNoOptions.instance_variable_set(:@default_options, nil)
+        FaradayMiddlewareSubclasses::SubclassOneOption.instance_variable_set(:@default_options, nil)
+        FaradayMiddlewareSubclasses::SubclassTwoOptions.instance_variable_set(:@default_options, nil)
+        Faraday::Middleware.instance_variable_set(:@default_options, nil)
+      end
+    end
+
+    after(:all) do
+      FaradayMiddlewareSubclasses::SubclassNoOptions.instance_variable_set(:@default_options, nil)
+      FaradayMiddlewareSubclasses::SubclassOneOption.instance_variable_set(:@default_options, nil)
+      FaradayMiddlewareSubclasses::SubclassTwoOptions.instance_variable_set(:@default_options, nil)
+      Faraday::Middleware.instance_variable_set(:@default_options, nil)
+    end
+
+    context 'with subclass DEFAULT_OPTIONS defined' do
+      include_context 'reset @default_options'
+
+      context 'and without application options configured' do
+        let(:resp1) { build_conn(:one_option).get('/success') }
+
+        it 'has only subclass defaults' do
+          expect(Faraday::Middleware.default_options).to eq(Faraday::Middleware::DEFAULT_OPTIONS)
+          expect(subclass_no_options.default_options).to eq(subclass_no_options::DEFAULT_OPTIONS)
+          expect(subclass_one_option.default_options).to eq(subclass_one_option::DEFAULT_OPTIONS)
+          expect(subclass_two_options.default_options).to eq(subclass_two_options::DEFAULT_OPTIONS)
+        end
+
+        it { expect(resp1.body).to eq('ok') }
+      end
+
+      context "and with one application's options changed" do
+        let(:resp2) { build_conn(:two_options).get('/success') }
+
+        before(:each) do
+          FaradayMiddlewareSubclasses::SubclassTwoOptions.default_options = { some_option: false }
+        end
+
+        it 'only updates default options of target subclass' do
+          expect(Faraday::Middleware.default_options).to eq(Faraday::Middleware::DEFAULT_OPTIONS)
+          expect(subclass_no_options.default_options).to eq(subclass_no_options::DEFAULT_OPTIONS)
+          expect(subclass_one_option.default_options).to eq(subclass_one_option::DEFAULT_OPTIONS)
+          expect(subclass_two_options.default_options).to eq({ some_option: false, some_other_option: false })
+        end
+
+        it { expect(resp2.body).to eq('ok') }
+      end
+
+      context "and with two applications' options changed" do
+        let(:resp1) { build_conn(:one_option).get('/success') }
+        let(:resp2) { build_conn(:two_options).get('/success') }
+
+        before(:each) do
+          FaradayMiddlewareSubclasses::SubclassOneOption.default_options = { some_other_option: true }
+          FaradayMiddlewareSubclasses::SubclassTwoOptions.default_options = { some_option: false }
+        end
+
+        it 'updates subclasses and parent independent of each other' do
+          expect(Faraday::Middleware.default_options).to eq(Faraday::Middleware::DEFAULT_OPTIONS)
+          expect(subclass_no_options.default_options).to eq(subclass_no_options::DEFAULT_OPTIONS)
+          expect(subclass_one_option.default_options).to eq({ some_other_option: true })
+          expect(subclass_two_options.default_options).to eq({ some_option: false, some_other_option: false })
+        end
+
+        it { expect(resp1.body).to eq('ok') }
+        it { expect(resp2.body).to eq('ok') }
+      end
+    end
+
+    context 'with FARADAY::MIDDLEWARE DEFAULT_OPTIONS and with Subclass DEFAULT_OPTIONS' do
+      before(:each) do
+        stub_const('Faraday::Middleware::DEFAULT_OPTIONS', { its_magic: false })
+      end
+
+      # Must stub Faraday::Middleware::DEFAULT_OPTIONS before resetting default options
+      include_context 'reset @default_options'
+
+      context 'and without application options configured' do
+        let(:resp1) { build_conn(:one_option).get('/success') }
+
+        it 'has only subclass defaults' do
+          expect(Faraday::Middleware.default_options).to eq(Faraday::Middleware::DEFAULT_OPTIONS)
+          expect(FaradayMiddlewareSubclasses::SubclassNoOptions.default_options).to eq({ its_magic: false })
+          expect(FaradayMiddlewareSubclasses::SubclassOneOption.default_options).to eq({ its_magic: false, some_other_option: false })
+          expect(FaradayMiddlewareSubclasses::SubclassTwoOptions.default_options).to eq({ its_magic: false, some_option: true, some_other_option: false })
+        end
+
+        it { expect(resp1.body).to eq('ok') }
+      end
+
+      context "and with two applications' options changed" do
+        let(:resp1) { build_conn(:one_option).get('/success') }
+        let(:resp2) { build_conn(:two_options).get('/success') }
+
+        before(:each) do
+          FaradayMiddlewareSubclasses::SubclassOneOption.default_options = { some_other_option: true }
+          FaradayMiddlewareSubclasses::SubclassTwoOptions.default_options = { some_option: false }
+        end
+
+        it 'updates subclasses and parent independent of each other' do
+          expect(Faraday::Middleware.default_options).to eq(Faraday::Middleware::DEFAULT_OPTIONS)
+          expect(FaradayMiddlewareSubclasses::SubclassNoOptions.default_options).to eq({ its_magic: false })
+          expect(FaradayMiddlewareSubclasses::SubclassOneOption.default_options).to eq({ its_magic: false, some_other_option: true })
+          expect(FaradayMiddlewareSubclasses::SubclassTwoOptions.default_options).to eq({ its_magic: false, some_option: false, some_other_option: false })
+        end
+
+        it { expect(resp1.body).to eq('ok') }
+        it { expect(resp2.body).to eq('ok') }
+      end
+    end
+
+    describe 'default_options input validation' do
+      include_context 'reset @default_options'
+
+      it 'raises error if Faraday::Middleware option does not exist' do
+        expect { Faraday::Middleware.default_options = { something_special: true } }.to raise_error(Faraday::InitializationError) do |e|
+          expect(e.message).to eq('Invalid options provided. Keys not found in Faraday::Middleware::DEFAULT_OPTIONS: something_special')
+        end
+      end
+
+      it 'raises error if subclass option does not exist' do
+        expect { subclass_one_option.default_options = { this_is_a_typo: true } }.to raise_error(Faraday::InitializationError) do |e|
+          expect(e.message).to eq('Invalid options provided. Keys not found in FaradayMiddlewareSubclasses::SubclassOneOption::DEFAULT_OPTIONS: this_is_a_typo')
+        end
+      end
+    end
+  end
 end

spec/faraday/response/raise_error_spec.rb

@@ -194,16 +194,60 @@
       end
     end
 
-    context 'when the include_request option is set to false' do
-      let(:middleware_options) { { include_request: false } }
-
-      it 'does not include request info in the exception' do
-        expect { perform_request }.to raise_error(Faraday::BadRequestError) do |ex|
-          expect(ex.response.keys).to contain_exactly(
-            :status,
-            :headers,
-            :body
-          )
+    describe 'DEFAULT_OPTION: include_request' do
+      before(:each) do
+        Faraday::Response::RaiseError.instance_variable_set(:@default_options, nil)
+        Faraday::Middleware.instance_variable_set(:@default_options, nil)
+      end
+
+      after(:all) do
+        Faraday::Response::RaiseError.instance_variable_set(:@default_options, nil)
+        Faraday::Middleware.instance_variable_set(:@default_options, nil)
+      end
+
+      context 'when RaiseError DEFAULT_OPTION (include_request: true) is used' do
+        it 'includes request info in the exception' do
+          expect { perform_request }.to raise_error(Faraday::BadRequestError) do |ex|
+            expect(ex.response.keys).to contain_exactly(
+              :status,
+              :headers,
+              :body,
+              :request
+            )
+          end
+        end
+      end
+
+      context 'when application sets default_options `include_request: false`' do
+        before(:each) do
+          Faraday::Response::RaiseError.default_options = { include_request: false }
+        end
+
+        context 'and when include_request option is omitted' do
+          it 'does not include request info in the exception' do
+            expect { perform_request }.to raise_error(Faraday::BadRequestError) do |ex|
+              expect(ex.response.keys).to contain_exactly(
+                :status,
+                :headers,
+                :body
+              )
+            end
+          end
+        end
+
+        context 'and when include_request option is explicitly set for instance' do
+          let(:middleware_options) { { include_request: true } }
+
+          it 'includes request info in the exception' do
+            expect { perform_request }.to raise_error(Faraday::BadRequestError) do |ex|
+              expect(ex.response.keys).to contain_exactly(
+                :status,
+                :headers,
+                :body,
+                :request
+              )
+            end
+          end
         end
       end
     end

spec/support/faraday_middleware_subclasses.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module FaradayMiddlewareSubclasses
+  class SubclassNoOptions < Faraday::Middleware
+  end
+
+  class SubclassOneOption < Faraday::Middleware
+    DEFAULT_OPTIONS = { some_other_option: false }.freeze
+  end
+
+  class SubclassTwoOptions < Faraday::Middleware
+    DEFAULT_OPTIONS = { some_option: true, some_other_option: false }.freeze
+  end
+end
+
+Faraday::Response.register_middleware(no_options: FaradayMiddlewareSubclasses::SubclassNoOptions)
+Faraday::Response.register_middleware(one_option: FaradayMiddlewareSubclasses::SubclassOneOption)
+Faraday::Response.register_middleware(two_options: FaradayMiddlewareSubclasses::SubclassTwoOptions)