Fix unwanted model retention when using class methods from Turbo::Broadcastable with locals

app/models/concerns/turbo/broadcastable.rb

@@ -518,7 +518,7 @@ def broadcast_rendering_with_defaults(options)
       options.tap do |o|
         # Add the current instance into the locals with the element name (which is the un-namespaced name)
         # as the key. This parallels how the ActionView::ObjectRenderer would create a local variable.
-        o[:locals] = (o[:locals] || {}).reverse_merge!(model_name.element.to_sym => self).compact
+        o[:locals] = (o[:locals] || {}).reverse_merge(model_name.element.to_sym => self).compact
 
         if o[:html] || o[:partial]
           return o

test/dummy/app/models/comment.rb

@@ -5,5 +5,6 @@ class Comment < ApplicationRecord
 
   broadcasts_to ->(comment) { [comment.article, :comments] },
     target: ->(comment) { "article_#{comment.article_id}_comments" },
-    partial: "comments/different_comment"
+    partial: "comments/different_comment",
+    locals: { highlight: true }
 end

test/streams/broadcastable_test.rb

@@ -441,6 +441,23 @@ class Turbo::BroadcastableCommentTest < ActionCable::Channel::TestCase
     end
   end
 
+  test "creating a second comment while using locals broadcasts the second comment" do
+    stream = "#{@article.to_gid_param}:comments"
+    target = "article_#{@article.id}_comments"
+
+    assert_broadcast_on stream, turbo_stream_action_tag("append", target: target, template: %(<p class="different">comment</p>\n)) do
+      perform_enqueued_jobs do
+        @article.comments.create!(body: "comment")
+      end
+    end
+
+    assert_broadcast_on stream, turbo_stream_action_tag("append", target: target, template: %(<p class="different">another comment</p>\n)) do
+      perform_enqueued_jobs do
+        @article.comments.create!(body: "another comment")
+      end
+    end
+  end
+
   test "updating a comment broadcasts" do
     comment = @article.comments.create!(body: "random")
     stream = "#{@article.to_gid_param}:comments"