ERB leading newline / whitespace supression with hyphen does not work as documented.

[cirosantilli]

The docs for 4.1.5 say http://api.rubyonrails.org/classes/ActionView/Base.html:

<%- and -%> suppress leading and trailing whitespace, including the trailing newline

However I have tested with things like:

a
<%- true %>b

a
<%- true -%>b

and the leading newline does not get removed. Am I doing something wrong, or is it a documentation bug?

My tests:

• view: https://github.com/cirosantilli/rails-cheat/blob/19c6fb1b92a2a14cecf117a94089d5d2e4e34ed0/app/app/views/controller0/action0.html.erb#L16
• assertions: https://github.com/cirosantilli/rails-cheat/blob/19c6fb1b92a2a14cecf117a94089d5d2e4e34ed0/app/test/controllers/controller0_controller_test.rb#L231

I have the same behavior for pure Ruby 2.1 ERB, which I think Rails is using with trim_options = '-'. But it seems that Rails does some preprocessing (pure Ruby does not remove trailing spaces: only the newline), so I'm not sure it it's relevant.

[rafaelfranca]

It only remove the line it is present if it is empty. Also this is a behaviour of erubis not Rails

[cirosantilli]

OK finally I understand: erubis removes the line of <%- only if it's the only thing on that line:

a\n <%- true %> \nb

becomes:

a\nb

@rafaelfranca can I make a PR to say on the docs http://api.rubyonrails.org/classes/ActionView/Base.html that Rails uses erubis and link to it's doc so that people can find out precisely how the templates work? Otherwise it is too hard to find out.

[rafaelfranca]

Sure! Feel free to open a PR updating the documentation.