Erubi is a ERB template engine for ruby. It is a simplified fork of Erubis, using the same basic algorithm, with the following differences:

• Handles postfix conditionals when using escaping (e.g. <%= foo if bar %>)

• Supports frozen_string_literal: true in templates via :freeze option

• Works with ruby’s --enable-frozen-string-literal option

• Automatically freezes strings for template text when ruby optimizes it (on ruby 2.1+)

• Escapes ' (apostrophe) when escaping for better XSS protection

• Has 6x faster escaping on ruby 2.3+ by using cgi/escape

• Has 81% smaller memory footprint (calculated using ObjectSpace.memsize_of_all)

• Does no monkey patching (Erubis adds a method to Kernel)

• Uses an immutable design (all options passed to the constructor, which returns a frozen object)

• Has simpler internals (1 file, <150 lines of code)

• Is not dead (Erubis hasn’t been updated since 2011)

It is not designed with Erubis API compatibility in mind, though most Erubis ERB syntax works, with the following exceptions:

• No support for <%=== for debug output

gem install erubi

Source code is available on GitHub at github.com/jeremyevans/erubi

Erubi only has built in support for retrieving the generated source for a file:

require 'erubi'
eval(Erubi::Engine.new(File.read('filename.erb')).src)

Most users will probably use Erubi via Rails or Tilt. Erubi is the default erb template handler in Tilt 2.0.6+ and Rails 5.1+.

Erubi does not support capturing block output into the template by default. However, it comes with an erubi/capture_end file that supports capturing via <%|= and <%|== tags which are closed with a <%| tag:

<%|= form do %>
  <input>
<%| end %>

This offers similar functionality to that offered by Rails’ <%= tags, but without the corner cases with that approach (which are due to attempting to parse ruby code via a regexp). Similar to the <%= and <%== tags, <%|= captures by default and <%|== captures and escapes by default, but this can be reversed via the :escape_capture or :escape options.

To use the capture_end support with tilt:

require 'tilt'
require 'erubi/capture_end'
Tilt.new("filename.erb", :engine_class=>Erubi::CaptureEndEngine).render

When using the capture_end support, any methods (such as form in the example above) should return the (potentially modified) buffer. Since the buffer variable is a local variable and not an instance variable by default, you’ll probably want to set the :bufvar variable when using the capture_end support to an instance variable, and have any methods used access that instance variable. Example:

def form
  @_buf << "<form>"
  yield
  @_buf << "</form>"
  @_buf
end

puts eval(Erubi::CaptureEndEngine.new(<<-END, :bufvar=>:@_buf).src)
before
<%|= form do %>
inside
<%| end %>
after
END

# Output:
# before
# <form>
# inside
# </form>
# after

Alternatively, passing the option :yield_returns_buffer => true will return the buffer captured by the block instead of the last expression in the block.

The bug tracker is located at github.com/jeremyevans/erubi/issues

MIT

Jeremy Evans <code@jeremyevans.net> kuwata-lab.com