DEPRECATION WARNING: Single arity template handlers are deprecated.

• ruby: 2.6.5
• Ruby on Rails: 6.0.0

db:migrate実行時に下記エラー。

# rails db:migrate
DEPRECATION WARNING: Single arity template handlers are deprecated. Template handlers must
now accept two parameters, the view object and the source for the view object.
Change:
  >> Coffee::Rails::TemplateHandler.call(template)
To:
  >> Coffee::Rails::TemplateHandler.call(template, source)
 (called from <main> at /myapp/rakefile:6)

下記issueによれば、coffee-railsを5.0.0にあげれば直るとのこと

DEPRECATION WARNING in new --edge app · Issue #452 · rails/jbuilder · GitHub

Gemfileを修正してインストールしたら直りました

# Gemfile

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 5.0.0'