Fix list_of helper with multi-line content

[zetaben]

Hello,

The current list_of helper in haml 5.0.1 seem to have an issue when running in rails (at least in 5.0.0.1) when inserting multi-line content.

In my rails app when I do a block link_to in the list_of, the content of the list is removed:

= list_of array do |type|               
  = link_to helper_url(type) do            
    = myhellper(type)                                         
    = type.humanize 

It seem to be linked to the use of strip! instead of strip the ! version will actually return nil if does nothing.

I managed to add a test that seem to replicate the issue without rails. It could also probably be fixed using an result.strip! || result which would not copy result.

Thanks again for HAML and saving me from ERB !

[k0kubun]

👍