ActionView::Helpers::FormBuilder extensions

Start to abstract validation message rendering by declare a descendant to the ActionView::Helpers::FormBuilder class named ValidationMessageFormBuilder. Set it as the application’s default by calling default_form_builder from the ApplicationController class.

First and foremost, declare the #errors method, which retrieves validation messages for an attribute. When passed a block, yield the collection of ActiveModel::Errors. When no block is passed, return the collection of ActiveModel::Errors.

Next, ensure that calls to form field builders set [aria-invalid="true"] when rendering a field with error associated to the attribute. When rendering checked-capable fields like <input type="checkbox"> and <input type="radio">, only render [aria-invalid="true"] on the element that is also checked.


      app/controllers/application_controller.rb

diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 9ebbc14..d2e3413 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -1,5 +1,9 @@
+require "./lib/validation_message_form_builder"
+
 class ApplicationController < ActionController::Base
   include FlashParams
 
   before_action { Current.user = Authentication.find(session) }
+
+  default_form_builder ValidationMessageFormBuilder
 end


      app/views/authentications/new.html.erb

diff --git a/app/views/authentications/new.html.erb b/app/views/authentications/new.html.erb
index fb2f95a..7972cb5 100644
--- a/app/views/authentications/new.html.erb
+++ b/app/views/authentications/new.html.erb
@@ -1,26 +1,24 @@
 <%= form_with(model: authentication) do |form| %>
-  <% form.object.errors[:base].tap do |errors| %>
+  <% form.errors(:base) do |errors| %>
     <% if errors.any? %>
       <%= tag.span errors.to_sentence, aria: { live: "assertive" } %>
     <% end %>
   <% end %>
 
-  <% form.object.errors[:username].tap do |errors| %>
+  <% form.errors(:username) do |errors| %>
     <%= form.label :username %>
     <%= form.text_field :username, aria: {
       describedby: {form.field_id(:username, :validation_message) => errors.any?},
-      invalid: errors.any?
     } %>
     <% if errors.any? %>
       <%= tag.span errors.to_sentence, id: form.field_id(:username, :validation_message) %>
     <% end %>
   <% end %>
 
-  <% form.object.errors[:password].tap do |errors| %>
+  <% form.errors(:password) do |errors| %>
     <%= form.label :password %>
     <%= form.password_field :password, aria: {
       describedby: {form.field_id(:password, :validation_message) => errors.any?},
-      invalid: errors.any?
     } %>
     <% if errors.any? %>
       <%= tag.span errors.to_sentence, id: form.field_id(:password, :validation_message) %>


      app/views/messages/index.html.erb

diff --git a/app/views/messages/index.html.erb b/app/views/messages/index.html.erb
index 49bfab9..5b072a8 100644
--- a/app/views/messages/index.html.erb
+++ b/app/views/messages/index.html.erb
@@ -6,11 +6,10 @@
 
 <% if Current.user %>
   <%= form_with model: message do |form| %>
-    <% form.object.errors[:content].tap do |errors| %>
+    <% form.errors(:content) do |errors| %>
       <%= form.label :content %>
       <%= form.rich_text_area :content, aria: {
         describedby: {form.field_id(:content, :validation_message) => errors.any?},
-        invalid: errors.any?
       } %>
       <% if errors.any? %>
         <%= tag.span errors.to_sentence, id: form.field_id(:content, :validation_message) %>


      config/initializers/rails.rb

diff --git a/config/initializers/rails.rb b/config/initializers/rails.rb
new file mode 100644
index 0000000..79526f7
--- /dev/null
+++ b/config/initializers/rails.rb
@@ -0,0 +1 @@
+Dir[Rails.root.join("lib", "rails_ext", "*")].each { |path| require "rails_ext/#{File.basename(path)}" }


      lib/rails_ext/action_view.rb

diff --git a/lib/rails_ext/action_view.rb b/lib/rails_ext/action_view.rb
new file mode 100644
index 0000000..b09d171
--- /dev/null
+++ b/lib/rails_ext/action_view.rb
@@ -0,0 +1,47 @@
+module AriaTagsExtension
+  def render
+    if object.respond_to?(:errors) && object.errors[@method_name].any?
+      @options["aria-invalid"] ||= "true"
+    end
+
+    super
+  end
+end
+
+module CheckableAriaTagsExtension
+  def render
+    if object.respond_to?(:errors) && object.errors[@method_name].any?
+      @options["aria-invalid"] ||= ("true" if @options["checked"])
+    end
+
+    super
+  end
+end
+
+ActiveSupport.on_load :action_view do
+  module ActionView
+    module Helpers
+      module Tags
+        class ActionText
+          prepend AriaTagsExtension
+        end
+
+        class Select
+          prepend AriaTagsExtension
+        end
+
+        class TextField
+          prepend AriaTagsExtension
+        end
+
+        class TextArea
+          prepend AriaTagsExtension
+        end
+
+        [RadioButton, CheckBox].each do |kls|
+          prepend CheckableAriaTagsExtension
+        end
+      end
+    end
+  end
+end


      lib/validation_message_form_builder.rb

diff --git a/lib/validation_message_form_builder.rb b/lib/validation_message_form_builder.rb
new file mode 100644
index 0000000..4851981
--- /dev/null
+++ b/lib/validation_message_form_builder.rb
@@ -0,0 +1,7 @@
+class ValidationMessageFormBuilder < ActionView::Helpers::FormBuilder
+  def errors(field, &block)
+    validation_messages = object.respond_to?(:errors) ? object.errors[field] : []
+
+    block ? yield(validation_messages) : validation_messages
+  end
+end