Never return stored content from content_for when a block is given

[tomstuart]

There is a bug in content_for. It should only return stored content when no block has been provided, but instead it returns stored content when the block generates a blank buffer and has a nil return value, which is what happens in a situation like this:

<% content_for :foo do %>
  <% if something_falsy %>
    foo
  <% end %>
  <% if something_else_falsy %>
    bar
  <% end %>
<% end %>

Ultimately this is because capture returns nil (vs '') when the resulting buffer is blank?, but that's apparently intended behaviour, so it's better to fix content_for to explicitly check block_given? rather than relying on the truthiness of capture(&block).

The bug provokes a deprecation warning in 3.0.x (see #2794); there is no such warning in 3.1.x, but it's still unintended behaviour.

[josevalim]

Sounds great. Can we have a patch for master as well?

[spastorino]

@tomstuart patch looks good. Just one thing please provide pull requests for master only next time, unless is something specific for 3-1-stable. If we need it for 3-1-stable we will backport or ask you to do so :). Thanks for your work ❤️

[spastorino]

I've already ported to master, thanks again