ruby-on-rails - 表单在 HAML 中无法正确呈现

Question

所以我有这个用haml写的表格

 = form_tag assign_photographers_path, class: "col-md-12 assign-photographers-form-#{portfolio.id}" do
   = hidden_field_tag :portfolio_id, portfolio.id
   = hidden_field_tag :user_id_1, "", class: "user_id_1"
   = hidden_field_tag :user_id_2, "", class: "user_id_2"
   = label_tag :user, "Begin typing to assign the first photographer:"
   %br
   .col-md-8.col-md-offset-2
   = text_field_tag :user, nil, class: "form-control photographer-search", data_id: portfolio.id
   .clearfix
   %div{class: "photographer-list#{portfolio.id} col-md-6 col-md-offset-3"}
     %h3 Chosen photographers
   .clearfix
   %br
   = submit_tag "Assign Photographers", :class => "btn btn-primary"

在源代码中它显示

<form accept-charset="UTF-8" action="/photographers/assign" class="col-md-12 assign-photographers-form-19" method="post"></form>

然后将表格的内容打印在表格下方。我不知道为什么它在表单标签之外打印。代码有什么问题，我该如何解决？