[SQUASH LATER] Validate default_form_attributes config argument

bootstrap_form.gemspec

@@ -15,6 +15,8 @@ Gem::Specification.new do |s|
                   "easy to create beautiful-looking forms using Bootstrap 4"
   s.license     = "MIT"
 
+  s.post_install_message = "Default form attribute role=\"form\" will be dropped in 5.0.0"
+
   s.files = `git ls-files -z`.split("\x0").reject do |f|
     f.match(%r{^(test)/})
   end

lib/bootstrap_form/configuration.rb

@@ -2,16 +2,22 @@
 
 module BootstrapForm
   class Configuration
-    DEFAULT = {
-      default_form_attributes: {
-        role: "form"
-      }
-    }.freeze
+    def default_form_attributes=(attributes)
+      case attributes
+      when nil
+        @default_form_attributes = {}
+      when Hash
+        @default_form_attributes = attributes
+      else
+        raise ArgumentError, "Unsupported default_form_attributes #{attributes.inspect}"
+      end
+    end
 
-    DEFAULT.keys.each { |key| attr_accessor key }
+    def default_form_attributes
+      return @default_form_attributes if defined? @default_form_attributes
 
-    def initialize
-      DEFAULT.each { |key, value| send("#{key}=", value) }
+      # TODO: Return blank hash ({}) in 5.0.0. Role "form" for form tags is redundant and makes W3C to raise a warning.
+      { role: "form" }
     end
   end
 end

test/bootstrap_configuration_test.rb

@@ -7,10 +7,26 @@ class BootstrapConfigurationTest < ActionView::TestCase
     assert_equal({ role: "form" }, config.default_form_attributes)
   end
 
-  test "allows to set default_form_attributes" do
+  test "allows to set default_form_attributes with custom value" do
     config = BootstrapForm::Configuration.new
     config.default_form_attributes = { foo: "bar" }
 
     assert_equal({ foo: "bar" }, config.default_form_attributes)
   end
+
+  test "allows to set default_form_attributes with nil" do
+    config = BootstrapForm::Configuration.new
+    config.default_form_attributes = nil
+
+    assert_equal({ }, config.default_form_attributes)
+  end
+
+  test "does not allow to set default_form_attributes with unsupported value" do
+    config = BootstrapForm::Configuration.new
+
+    exception = assert_raises ArgumentError do
+      config.default_form_attributes = [1,2,3]
+    end
+    assert_equal('Unsupported default_form_attributes [1, 2, 3]', exception.message)
+  end
 end