Merge pull request rails#44328 from seanpdoyle/form-for-to-model

`form_for`: Attempt to call `to_model` on first argument

Author: gmcgibbon

actionview/CHANGELOG.md

@@ -1,3 +1,5 @@
+*   Ensure models passed to `form_for` attempt to call `to_model`.
 
+    *Sean Doyle*
 
 Please check [7-0-stable](https://github.com/rails/rails/blob/7-0-stable/actionview/CHANGELOG.md) for previous changes.

actionview/lib/action_view/helpers/form_helper.rb

@@ -438,7 +438,7 @@ def form_for(record, options = {}, &block)
           model       = nil
           object_name = record
         else
-          model       = record
+          model       = convert_to_model(record)
           object      = _object_for_form_builder(record)
           raise ArgumentError, "First argument in form cannot contain nil or be empty" unless object
           object_name = options[:as] || model_name_from_record_or_class(object).param_key

actionview/test/template/form_helper/form_with_test.rb

@@ -309,6 +309,7 @@ def @post.to_param; "123"; end
     @controller.singleton_class.include Routes.url_helpers
   end
 
+  RecordForm = Struct.new(:to_model, keyword_init: true)
   Routes = ActionDispatch::Routing::RouteSet.new
   Routes.draw do
     resources :posts do
@@ -381,6 +382,26 @@ def test_form_with
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_with_with_persisted_to_model
+    post_form = RecordForm.new(to_model: @post)
+
+    form_with(model: post_form) { }
+
+    expected = whole_form("/posts/123", method: :post) { "" }
+
+    assert_dom_equal expected, output_buffer
+  end
+
+  def test_form_with_with_new_record_to_model
+    post_form = RecordForm.new(to_model: Post.new)
+
+    form_with(model: post_form) { }
+
+    expected = whole_form("/posts", method: :post) { "" }
+
+    assert_dom_equal expected, output_buffer
+  end
+
   def test_form_with_button_yields_translation
     form_with(model: @post) do |f|
       concat(f.button { |value| concat content_tag(:span, value) })

actionview/test/template/form_helper_test.rb

@@ -143,6 +143,7 @@ def @post.to_param; "123"; end
     @controller.singleton_class.include Routes.url_helpers
   end
 
+  RecordForm = Struct.new(:to_model, keyword_init: true)
   Routes = ActionDispatch::Routing::RouteSet.new
   Routes.draw do
     resources :posts do
@@ -2076,6 +2077,26 @@ def post.tag_ids; [1]; end
     assert_dom_equal expected, output_buffer
   end
 
+  def test_form_for_with_persisted_to_model
+    post_form = RecordForm.new(to_model: @post)
+
+    form_for(post_form) { }
+
+    expected = whole_form("/posts/123", "edit_post_123", "edit_post", method: :patch) { "" }
+
+    assert_dom_equal expected, output_buffer
+  end
+
+  def test_form_for_with_new_record_to_model
+    post_form = RecordForm.new(to_model: Post.new)
+
+    form_for(post_form) { }
+
+    expected = whole_form("/posts", "new_post", "new_post", method: :post) { "" }
+
+    assert_dom_equal expected, output_buffer
+  end
+
   def test_form_for_with_file_field_generate_multipart
     form_for(@post, html: { id: "create-post" }) do |f|
       concat f.file_field(:file)