Validate configuration when applied

lib/kangaru/application.rb

@@ -2,6 +2,8 @@ module Kangaru
   class Application
     extend Forwardable
 
+    class InvalidConfigError < StandardError; end
+
     attr_reader :paths, :namespace, :database
 
     attr_accessor :config_path
@@ -38,6 +40,8 @@ def apply_config!
 
       config.import!(config_path) unless config_path.nil?
 
+      validate_config!
+
       @database = setup_database!
       @configured = true
     end
@@ -73,6 +77,14 @@ def autoloader
       end
     end
 
+    def validate_config!
+      return if config.valid?
+
+      message = config.errors.map(&:full_message).join(", ")
+
+      raise InvalidConfigError, message
+    end
+
     def setup_database!
       return unless config.database.adaptor
 

sig/kangaru/application.rbs

@@ -2,6 +2,9 @@ module Kangaru
   class Application
     extend Forwardable
 
+    class InvalidConfigError < StandardError
+    end
+
     attr_reader paths: Paths
     attr_reader namespace: Module
     attr_reader config: Config
@@ -34,6 +37,8 @@ module Kangaru
 
     attr_reader autoloader: Zeitwerk::Loader
 
+    def validate_config!: -> void
+
     def setup_database!: -> Database?
   end
 end

spec/features/configuration_spec.rb

@@ -125,7 +125,27 @@ class TestConfigurator < Kangaru::Configurator
   describe "applying config" do
     subject(:apply_config!) { SomeGem.apply_config! }
 
-    let(:configuration) { nil }
+    let(:configuration) do
+      configure_block do
+        <<~RUBY
+          config.test.required_attribute = :some_value
+        RUBY
+      end
+    end
+
+    let(:configurator_class) do
+      <<~RUBY
+        module SomeGem
+          module Configurators
+            class TestConfigurator < Kangaru::Configurator
+              attr_accessor :required_attribute
+
+              validates :required_attribute, required: true
+            end
+          end
+        end
+      RUBY
+    end
 
     before { gem.load! }
 
@@ -138,8 +158,29 @@ class TestConfigurator < Kangaru::Configurator
     end
 
     context "when config is applied once" do
-      it "does not raise any errors" do
-        expect { apply_config! }.not_to raise_error
+      context "and config is not valid" do
+        let(:configuration) { nil }
+
+        it "raises an error" do
+          expect { apply_config! }.to raise_error(
+            Kangaru::Application::InvalidConfigError,
+            "Required attribute can't be blank"
+          )
+        end
+      end
+
+      context "and config is valid" do
+        let(:configuration) do
+          configure_block do
+            <<~RUBY
+              config.test.required_attribute = :some_value
+            RUBY
+          end
+        end
+
+        it "does not raise any errors" do
+          expect { apply_config! }.not_to raise_error
+        end
       end
     end
   end

spec/kangaru/application_spec.rb

@@ -180,13 +180,22 @@
 
     let(:database) { instance_spy(Kangaru::Database) }
 
+    let(:config_valid?) { true }
+    let(:config_errors) { [] }
+
     before do
       allow(Kangaru::Database).to receive(:new).and_return(database)
 
-      allow(application.config).to receive(:import!)
+      allow(application.config).to receive_messages(
+        import!: nil, valid?: config_valid?, errors: config_errors
+      )
     end
 
     shared_examples :configures_application do
+      it "does not raise any errors" do
+        expect { apply_config! }.not_to raise_error
+      end
+
       it "marks the application as configured" do
         expect { apply_config! }
           .to change { application.configured? }
@@ -255,48 +264,71 @@
     end
 
     context "when config has not already been applied" do
-      before do
-        application.config_path = config_path
-        application.config.database.adaptor = adaptor
-      end
+      context "and config is invalid" do
+        let(:config_valid?) { false }
 
-      context "and config path is not set" do
-        let(:config_path) { nil }
+        let(:config_errors) do
+          [Kangaru::Validation::Error.new(attribute:, type:)]
+        end
 
-        context "and database adaptor is not set" do
-          let(:adaptor) { nil }
+        let(:attribute) { :some_attribute }
+        let(:type)      { :blank }
 
-          include_examples :configures_application
-          include_examples :does_not_set_up_database
-          include_examples :does_not_import_external_config
+        it "raises an error" do
+          expect { apply_config! }.to raise_error(
+            described_class::InvalidConfigError,
+            "Some attribute can't be blank"
+          )
         end
+      end
 
-        context "and database adaptor is set" do
-          let(:adaptor) { :sqlite }
+      context "and config is valid" do
+        let(:valid?) { true }
+        let(:errors) { [] }
 
-          include_examples :configures_application
-          include_examples :sets_up_database
-          include_examples :does_not_import_external_config
+        before do
+          application.config_path = config_path
+          application.config.database.adaptor = adaptor
         end
-      end
 
-      context "and config path is set" do
-        let(:config_path) { "/foo/bar/config.yml" }
+        context "and config path is not set" do
+          let(:config_path) { nil }
+
+          context "and database adaptor is not set" do
+            let(:adaptor) { nil }
+
+            include_examples :configures_application
+            include_examples :does_not_set_up_database
+            include_examples :does_not_import_external_config
+          end
 
-        context "and database adaptor is not set" do
-          let(:adaptor) { nil }
+          context "and database adaptor is set" do
+            let(:adaptor) { :sqlite }
 
-          include_examples :configures_application
-          include_examples :does_not_set_up_database
-          include_examples :imports_external_config
+            include_examples :configures_application
+            include_examples :sets_up_database
+            include_examples :does_not_import_external_config
+          end
         end
 
-        context "and database adaptor is set" do
-          let(:adaptor) { :sqlite }
+        context "and config path is set" do
+          let(:config_path) { "/foo/bar/config.yml" }
+
+          context "and database adaptor is not set" do
+            let(:adaptor) { nil }
+
+            include_examples :configures_application
+            include_examples :does_not_set_up_database
+            include_examples :imports_external_config
+          end
+
+          context "and database adaptor is set" do
+            let(:adaptor) { :sqlite }
 
-          include_examples :configures_application
-          include_examples :sets_up_database
-          include_examples :imports_external_config
+            include_examples :configures_application
+            include_examples :sets_up_database
+            include_examples :imports_external_config
+          end
         end
       end
     end