feat(can_have_try_result): introduce Service.try_result

lib/convenient_service/service/plugins/can_have_try_result/concern.rb

@@ -9,6 +9,25 @@ module Concern
 
           instance_methods do
             ##
+            # Returns `ConvenientService::Service::Plugins::HasResult::Entities::Result` when overridden.
+            #
+            # @raise [ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden]
+            #
+            # @internal
+            #   NOTE: name is inspired by Ruby's `try_convert` methods.
+            #   - https://blog.saeloun.com/2021/08/03/ruby-adds-integer-try-convert
+            #
+            #   TODO: A plugin that checks that a `success` is returned from `try_result`.
+            #
+            def try_result
+              raise Errors::TryResultIsNotOverridden.new(service: self)
+            end
+          end
+
+          class_methods do
+            ##
+            # Returns `ConvenientService::Service::Plugins::HasResult::Entities::Result` when `#try_result` is overridden.
+            #
             # @raise [ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden]
             #
             # @example `try_result` method MUST always return `success` with reasonable "null" data.
@@ -60,14 +79,8 @@ module Concern
             # @see https://thoughtbot.com/blog/rails-refactoring-example-introduce-null-object
             # @see https://en.wikipedia.org/wiki/Null_object_pattern
             #
-            # @internal
-            #   NOTE: name is inspired by Ruby's `try_convert` methods.
-            #   - https://blog.saeloun.com/2021/08/03/ruby-adds-integer-try-convert
-            #
-            #   TODO: A plugin that checks that a `success` is returned from `try_result`.
-            #
-            def try_result
-              raise Errors::TryResultIsNotOverridden.new(service: self)
+            def try_result(...)
+              new(...).try_result
             end
           end
         end

spec/lib/convenient_service/service/plugins/can_have_try_result/concern_spec.rb

@@ -5,6 +5,27 @@
 require "convenient_service"
 
 RSpec.describe ConvenientService::Service::Plugins::CanHaveTryResult::Concern do
+  include ConvenientService::RSpec::Matchers::DelegateTo
+
+  let(:service_class) do
+    Class.new do
+      include ConvenientService::Configs::Standard
+
+      ##
+      # TODO: Remove once `CanHaveTryResult` becomes included into `Standard` config.
+      #
+      concerns do
+        use ConvenientService::Service::Plugins::CanHaveTryResult::Concern
+      end
+    end
+  end
+
+  let(:service_instance) { service_class.new }
+
+  let(:args) { [:foo] }
+  let(:kwargs) { {foo: :bar} }
+  let(:block) { proc { :foo } }
+
   example_group "modules" do
     include ConvenientService::RSpec::Matchers::IncludeModule
 
@@ -28,33 +49,38 @@
   end
 
   example_group "instance methods" do
-    let(:service_class) do
-      Class.new do
-        include ConvenientService::Configs::Standard
-
-        ##
-        # TODO: Remove once `CanHaveTryResult` becomes included into `Standard` config.
-        #
-        concerns do
-          use ConvenientService::Service::Plugins::CanHaveTryResult::Concern
-        end
+    describe "#try_result" do
+      let(:error_message) do
+        <<~TEXT
+          Try result method (#try_result) of `#{service_class}` is NOT overridden.
+
+          NOTE: Make sure overridden `try_result` returns `success` with reasonable "null" data.
+        TEXT
       end
-    end
 
-    let(:service_instance) { service_class.new }
+      it "raises `ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden`" do
+        expect { service_instance.try_result }
+          .to raise_error(ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden)
+          .with_message(error_message)
+      end
+    end
+  end
 
-    let(:error_message) do
-      <<~TEXT
-        Try result method (#try_result) of `#{service_class}` is NOT overridden.
+  example_group "class methods" do
+    describe ".try_result" do
+      specify do
+        expect { ignoring_error(ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden) { service_class.try_result(*args, **kwargs, &block) } }
+          .to delegate_to(service_class, :new)
+          .with_arguments(*args, **kwargs, &block)
+      end
 
-        NOTE: Make sure overridden `try_result` returns `success` with reasonable "null" data.
-      TEXT
-    end
+      specify do
+        allow(service_class).to receive(:new).and_return(service_instance)
 
-    it "raises `ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden`" do
-      expect { service_instance.try_result }
-        .to raise_error(ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden)
-        .with_message(error_message)
+        expect { ignoring_error(ConvenientService::Service::Plugins::CanHaveTryResult::Errors::TryResultIsNotOverridden) { service_class.try_result(*args, **kwargs, &block) } }
+          .to delegate_to(service_instance, :try_result)
+          .and_return_its_value
+      end
     end
   end
 end

spec/lib/convenient_service/service/plugins/has_result/concern/class_methods_spec.rb

@@ -53,6 +53,7 @@ def result
   end
 
   let(:service_instance) { service_class.new(*args, **kwargs, &block) }
+
   let(:args) { [:foo] }
   let(:kwargs) { {foo: :bar} }
   let(:block) { proc { :foo } }