Merge PR rails#42755

Author: rafaelfranca

actionview/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Execute the `ActionView::Base.field_error_proc` within the context of the
+    `ActionView::Base` instance:
+
+    ```ruby
+    config.action_view.field_error_proc = proc { |html| content_tag(:div, html, class: "field_with_errors") }
+    ```
+
+    *Sean Doyle*
+
 *   Add support for `button_to ..., authenticity_token: false`
 
     ```ruby

actionview/lib/action_view/base.rb

@@ -142,7 +142,7 @@ class Base
     include Helpers, ::ERB::Util, Context
 
     # Specify the proc used to decorate input tags that refer to attributes with errors.
-    cattr_accessor :field_error_proc, default: Proc.new { |html_tag, instance| "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe }
+    cattr_accessor :field_error_proc, default: Proc.new { |html_tag, instance| content_tag :div, html_tag, class: "field_with_errors" }
 
     # How to complete the streaming when an exception occurs.
     # This is our best guess: first try to close the attribute, then the tag.

actionview/lib/action_view/helpers/active_model_helper.rb

@@ -27,7 +27,7 @@ def tag(type, options, *)
 
       def error_wrapping(html_tag)
         if object_has_errors?
-          Base.field_error_proc.call(html_tag, self)
+          @template_object.instance_exec(html_tag, self, &Base.field_error_proc)
         else
           html_tag
         end

actionview/test/actionpack/controller/render_test.rb

@@ -33,6 +33,12 @@ def nested_partial_with_form_builder
   end
 end
 
+class ValidatingPost < Post
+  include ActiveModel::Validations
+
+  validates :title, presence: true
+end
+
 class TestController < ActionController::Base
   protect_from_forgery
 
@@ -487,6 +493,14 @@ def partial_with_form_builder
     render partial: ActionView::Helpers::FormBuilder.new(:post, nil, view_context, {})
   end
 
+  def partial_with_form_builder_and_invalid_model
+    post = ValidatingPost.new
+
+    post.validate
+
+    render partial: ActionView::Helpers::FormBuilder.new(:post, post, view_context, {})
+  end
+
   def partial_with_form_builder_subclass
     render partial: LabellingFormBuilder.new(:post, nil, view_context, {})
   end
@@ -680,6 +694,7 @@ class RenderTest < ActionController::TestCase
     get :partial_only, to: "test#partial_only"
     get :partial_with_counter, to: "test#partial_with_counter"
     get :partial_with_form_builder, to: "test#partial_with_form_builder"
+    get :partial_with_form_builder_and_invalid_model, to: "test#partial_with_form_builder_and_invalid_model"
     get :partial_with_form_builder_subclass, to: "test#partial_with_form_builder_subclass"
     get :partial_with_hash_object, to: "test#partial_with_hash_object"
     get :partial_with_locals, to: "test#partial_with_locals"
@@ -1300,6 +1315,44 @@ def test_partial_with_form_builder
     assert_equal "<label for=\"post_title\">Title</label>\n", @response.body
   end
 
+  def test_partial_with_form_builder_and_invalid_model
+    get :partial_with_form_builder_and_invalid_model
+
+    assert_equal <<~HTML.strip, @response.body.strip
+      <div class="field_with_errors"><label for="post_title">Title</label></div>
+    HTML
+  end
+
+  def test_partial_with_form_builder_and_invalid_model_custom_field_error_proc
+    old_proc = ActionView::Base.field_error_proc
+    ActionView::Base.field_error_proc = proc { |html| tag.div html, class: "errors" }
+
+    get :partial_with_form_builder_and_invalid_model
+
+    assert_equal <<~HTML.strip, @response.body.strip
+      <div class="errors"><label for="post_title">Title</label></div>
+    HTML
+  ensure
+    ActionView::Base.field_error_proc = old_proc if old_proc
+  end
+
+  def test_partial_with_form_builder_and_invalid_model_custom_rendering_field_error_proc
+    old_proc = ActionView::Base.field_error_proc
+    ActionView::Base.field_error_proc = proc do |html_tag, instance|
+      render inline: <<~ERB, locals: { html_tag: html_tag, instance: instance }
+        <div class="field_with_errors"><%= html_tag %> <span class="error"><%= [instance.error_message].join(', ') %></span></div>
+      ERB
+    end
+
+    get :partial_with_form_builder_and_invalid_model
+
+    assert_equal <<~HTML.strip, @response.body.strip
+      <div class="field_with_errors"><label for="post_title">Title</label> <span class="error">can&#39;t be blank</span></div>
+    HTML
+  ensure
+    ActionView::Base.field_error_proc = old_proc if old_proc
+  end
+
   def test_partial_with_form_builder_subclass
     get :partial_with_form_builder_subclass
     assert_equal "<label for=\"post_title\">Title</label>\n", @response.body

guides/source/configuring.md

@@ -1083,12 +1083,11 @@ Controls whether or not templates should be reloaded on each request. Defaults t
 
 #### `config.action_view.field_error_proc`
 
-Provides an HTML generator for displaying errors that come from Active Model. The default is
+Provides an HTML generator for displaying errors that come from Active Model. The block is evaluated within
+the context of an Action View template. The default is
 
 ```ruby
-Proc.new do |html_tag, instance|
-  %Q(<div class="field_with_errors">#{html_tag}</div>).html_safe
-end
+Proc.new { |html_tag, instance| content_tag :div, html_tag, class: "field_with_errors" }
 ```
 
 #### `config.action_view.default_form_builder`