your-console $ rake deprecated

lib/tasks/rails.rake

desc "Checks your app and gently warns you if you are using deprecated code."
task :deprecated => :environment do
deprecated = {
'@params' => 'Use params[] instead',
'@session' => 'Use session[] instead',
'@flash' => 'Use flash[] instead',
'@request' => 'Use request[] instead',
'@env' => 'Use env[] instead',
'find_all' => 'Use find(:all) instead',
'find_first' => 'Use find(:first) instead',
'render_partial' => 'Use render :partial instead',
'component' => 'Use of components are frowned upon',
'paginate' => 'The default paginator is slow. Writing your own may be faster',
'start_form_tag' => 'Use form_for instead',
'end_form_tag' => 'Use form_for instead',
':post => true' => 'Use :method => :post instead'
}

deprecated.each do |key, warning|
puts '--> ' + key
output = `cd '#{File.expand_path('app', RAILS_ROOT)}' && grep -n --exclude=*.svn* -r '#{key}' *`
unless output =~ /^$/
puts " !! " + warning + " !!"
puts ' ' + '.' * (warning.length + 6)
puts output
else
puts " Clean! Cheers for you!"
end
puts
end
end