Fix no _method input in form_for namespaced model

actionview/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Fix `form_for` missing the hidden `_method` input for models with a
+    namespaced route.
+
+    *Hartley McGuire*
+
 *   Fix `render collection: @records, cache: true` inside `jbuilder` templates
 
     The previous fix that shipped in `7.0.7` assumed template fragments are always strings,

actionview/lib/action_view/helpers/form_helper.rb

@@ -465,12 +465,13 @@ def apply_form_for_options!(object, options) # :nodoc:
 
         as = options[:as]
         namespace = options[:namespace]
-        action = object.respond_to?(:persisted?) && object.persisted? ? :edit : :new
+        action, method = object.respond_to?(:persisted?) && object.persisted? ? [:edit, :patch] : [:new, :post]
         options[:html] ||= {}
         options[:html].reverse_merge!(
           class:  as ? "#{action}_#{as}" : dom_class(object, action),
           id:     (as ? [namespace, action, as] : [namespace, dom_id(object, action)]).compact.join("_").presence,
         )
+        options[:method] ||= method
       end
       private :apply_form_for_options!
 

actionview/test/template/form_helper_test.rb

@@ -2148,6 +2148,26 @@ def test_form_for_with_new_record_to_model
     assert_dom_equal expected, @rendered
   end
 
+  def test_form_for_with_nested_persisted_to_model
+    post_form = RecordForm.new(to_model: @post)
+
+    form_for([:admin, post_form]) { }
+
+    expected = whole_form("/admin/posts/123", "edit_post_123", "edit_post", method: :patch) { "" }
+
+    assert_dom_equal expected, @rendered
+  end
+
+  def test_form_for_with_nested_new_record_to_model
+    post_form = RecordForm.new(to_model: Post.new)
+
+    form_for([:admin, post_form]) { }
+
+    expected = whole_form("/admin/posts", "new_post", "new_post", method: :post) { "" }
+
+    assert_dom_equal expected, @rendered
+  end
+
   def test_form_for_with_file_field_generate_multipart
     form_for(@post, html: { id: "create-post" }) do |f|
       concat f.file_field(:file)