Outputting an object directly on a tag is unexpectedly double escaped in v6

[DMA57361]

Came accross an inconsistency in how objects are output (esacaped?) after upgrading from 5.2.2 to 6.0.10.

For some unnecessary context: we use the draper gem to provide view decorators for objects and one of our apps uses these to have time objects output by default with a formatting with happens to include a non-breaking space, and after upgrading to v6 some - but not all! - were being double escaped.

I can reproduce the issue with the following setup added to a Rails 6.1 application. Given this class:

class Order
  def to_s
    "Order 1234 2022-11-29".html_safe
  end
end

If this HAML in placed into a view:

%div
  %p= Order.new
  %p
    = Order.new
  %p= Order.new.to_s
  %p
    = Order.new.to_s

The rendered HTML is:

<div>
<p>Order 1234&amp;nbsp;2022-11-29</p>
<p>
Order 1234&nbsp;2022-11-29
</p>
<p>Order 1234&nbsp;2022-11-29</p>
<p>
Order 1234&nbsp;2022-11-29
</p>
</div>

For clarity this is how it appears for the user:

Order 1234 2022-11-29
Order 1234 2022-11-29
Order 1234 2022-11-29
Order 1234 2022-11-29

It seems that outputting an object such that to_s is being called implicitly is not considering the haml_safe value of the string and is instead re-escaping it..? But it seems to only do this when output inline with a tag? Moving the same code to a nested location seems to render as expected, as does explicitly calling to_s in either position.

In version 5.2.2 all four timestamps are rendered correctly, with the ampersand not being incorrectly double escaped.

[k0kubun]

Fixed in 6.1.0.