Attempt to lazy-load component when container is asked for key?

This also adds `Container.registered?` which acts as `key?` used to.
Besides it, `Container.resove` not takes an optional block to make this interface constistent with dry-container

Gemfile

@@ -2,12 +2,13 @@
 
 source 'https://rubygems.org'
 
-git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
+git_source(:github) { |repo_name| "https://github.com/dry-rb/#{repo_name}" }
 
 gemspec
 
 gem 'bootsnap'
 gem 'dry-monitor'
+gem 'dry-container', github: 'dry-container'
 
 gem 'codeclimate-test-reporter', platforms: :mri
 

lib/dry/system/auto_registrar.rb

@@ -51,7 +51,7 @@ def components(dir)
         files(dir)
           .map { |file_name| [file_name, file_options(file_name)] }
           .map { |(file_name, options)| component(relative_path(dir, file_name), **options) }
-          .reject { |component| key?(component.identifier) }
+          .reject { |component| registered?(component.identifier) }
       end
 
       # @api private
@@ -81,8 +81,8 @@ def root
       end
 
       # @api private
-      def key?(name)
-        container.key?(name)
+      def registered?(name)
+        container.registered?(name)
       end
 
       # @api private

lib/dry/system/components/bootable.rb

@@ -191,7 +191,7 @@ def container
         # @api private
         def finalize
           lifecycle.container.each do |key, item|
-            container.register(key, item) unless container.key?(key)
+            container.register(key, item) unless container.registered?(key)
           end
           self
         end

lib/dry/system/container.rb

@@ -518,12 +518,37 @@ def root
         end
 
         # @api public
-        def resolve(key)
-          load_component(key) unless finalized?
+        def resolve(key, &block)
+          load_component(key, &block) unless finalized?
 
           super
         end
 
+        alias_method :registered?, :key?
+        #
+        # @!method registered?(key)
+        #   Whether a +key+ is registered (doesn't trigger loading)
+        #   @param [String,Symbol] key Identifier
+        #   @return [Boolean]
+        #   @api public
+        #
+
+        # Check if identifier is registered.
+        # If not, try to load the component
+        #
+        # @param [String,Symbol] key Identifier
+        # @return [Boolean]
+        #
+        # @api public
+        def key?(key)
+          if finalized?
+            registered?(key)
+          else
+            registered?(key) || resolve(key) { return false }
+            true
+          end
+        end
+
         # @api private
         def load_paths
           @load_paths ||= []
@@ -572,7 +597,7 @@ def component(identifier, **options)
 
         # @api private
         def require_component(component)
-          return if key?(component.identifier)
+          return if registered?(component.identifier)
 
           raise FileNotFoundError, component unless component.file_exists?(load_paths)
 
@@ -593,8 +618,8 @@ def require_path(path)
         end
 
         # @api private
-        def load_component(key)
-          return self if key?(key)
+        def load_component(key, &block)
+          return self if registered?(key)
 
           component(key).tap do |component|
             if component.boot?
@@ -608,7 +633,7 @@ def load_component(key)
                 load_imported_component(component.namespaced(root_key))
               end
 
-              load_local_component(component) unless key?(key)
+              load_local_component(component, &block) unless registered?(key)
             end
           end
 
@@ -641,17 +666,19 @@ def inherited(klass)
         private
 
         # @api private
-        def load_local_component(component, default_namespace_fallback = false)
+        def load_local_component(component, default_namespace_fallback = false, &block)
           if booter.bootable?(component) || component.file_exists?(load_paths)
             booter.boot_dependency(component) unless finalized?
 
             require_component(component) do
               register(component.identifier) { component.instance }
             end
           elsif !default_namespace_fallback
-            load_local_component(component.prepend(config.default_namespace), true)
+            load_local_component(component.prepend(config.default_namespace), true, &block)
           elsif manual_registrar.file_exists?(component)
             manual_registrar.(component)
+          elsif block_given?
+            yield
           else
             raise ComponentLoadError, component
           end

lib/dry/system/lifecycle.rb

@@ -126,7 +126,7 @@ def trigger!(name, &block)
 
       # @api private
       def method_missing(meth, *args, &block)
-        if target.key?(meth)
+        if target.registered?(meth)
           target[meth]
         elsif container.key?(meth)
           container[meth]

lib/dry/system/plugins/logging.rb

@@ -32,7 +32,7 @@ def self.extended(system)
         #
         # @api private
         def register_logger
-          if key?(:logger)
+          if registered?(:logger)
             self
           elsif config.logger
             register(:logger, config.logger)

lib/dry/system/plugins/notifications.rb

@@ -17,7 +17,7 @@ def self.dependencies
 
         # @api private
         def register_notifications
-          return self if key?(:notifications)
+          return self if registered?(:notifications)
 
           register(:notifications, Monitor::Notifications.new(config.name))
         end

spec/integration/container/plugins/logging_spec.rb

@@ -17,7 +17,7 @@
 
   context 'with default logger settings' do
     subject(:system) do
-      Class.new(Dry::System::Container) do
+      class Test::Container < Dry::System::Container
         use :env
         use :logging
       end

spec/unit/container/auto_register_spec.rb

@@ -20,7 +20,7 @@ class Test::Container < Dry::System::Container
     it { expect(Test::Container['bar.baz']).to be_an_instance_of(Bar::Baz) }
 
     it "doesn't register files with inline option 'auto_register: false'" do
-      expect(Test::Container.key?('no_register')).to eql false
+      expect(Test::Container.registered?('no_register')).to eql false
     end
   end
 
@@ -46,8 +46,8 @@ class Test::Container < Dry::System::Container
 
       expect(Test::Container['foo']).to eql('foo')
 
-      expect(Test::Container.key?('bar')).to eql false
-      expect(Test::Container.key?('bar.baz')).to eql false
+      expect(Test::Container.registered?('bar')).to eql false
+      expect(Test::Container.registered?('bar.baz')).to eql false
     end
   end
 

spec/unit/container/import_spec.rb

@@ -14,7 +14,7 @@
   it 'imports one container into another' do
     app.import(persistence: db)
 
-    expect(app.key?('persistence.users')).to be(false)
+    expect(app.registered?('persistence.users')).to be(false)
 
     app.finalize!
 

spec/unit/container_spec.rb

@@ -146,7 +146,7 @@ class Test::Container < Dry::System::Container
       container.init(:bar)
 
       expect(Test.const_defined?(:Bar)).to be(true)
-      expect(container.key?('test.bar')).to be(false)
+      expect(container.registered?('test.bar')).to be(false)
     end
   end
 
@@ -251,4 +251,61 @@ class Test::Container < Dry::System::Container
       end
     end
   end
+
+  describe '.key?' do
+    before do
+      class Test::FalseyContainer < Dry::System::Container
+        register(:else) { :else }
+        register(:false) { false }
+        register(:nil) { nil }
+      end
+
+      class Test::Container < Dry::System::Container
+        config.root = SPEC_ROOT.join('fixtures/test').realpath
+        load_paths!('lib')
+
+        importer.registry.update(falses: Test::FalseyContainer)
+      end
+    end
+
+    it 'tries to load component' do
+      expect(container.key?('test.dep')).to be(true)
+    end
+
+    it 'returns false for non-existing component' do
+      expect(container.key?('test.missing')).to be(false)
+    end
+
+    it 'returns true if registered value is false or nil' do
+      expect(container.key?('falses.false')).to be(true)
+      expect(container.key?('falses.nil')).to be(true)
+    end
+  end
+
+  describe '.resolve' do
+    before do
+      class Test::Container < Dry::System::Container
+        config.root = SPEC_ROOT.join('fixtures/test').realpath
+      end
+    end
+
+    it 'runs a fallback block when a component cannot be resolved' do
+      expect(container.resolve('missing') { :fallback }).to be(:fallback)
+    end
+  end
+
+  describe '.registered?' do
+    before do
+      class Test::Container < Dry::System::Container
+        config.root = SPEC_ROOT.join('fixtures/test').realpath
+        load_paths!('lib')
+      end
+    end
+
+    it 'checks if a component is registered' do
+      expect(container.registered?('test.dep')).to be(false)
+      container.resolve('test.dep')
+      expect(container.registered?('test.dep')).to be(true)
+    end
+  end
 end