Prevent ActionMailer to strip repeating spaces in plain message

Question

I'm trying to have an table in text mail, so I write some helpers:

module MailerHelper
  def field_width(text, width)
    ' ' * (width - text.length) + text
  end

  def cell(text, width)
    output = '| ' + field_width(text, width-2) + " |\n"
    output << '+-' + '-'*(width-2) + '-+'
  end
end

Then in view I write it like this:

<%= cell 'Test', 10 %>

But that what I get (according to letter_opener) is:

| Test |
+----------+

As can you see, the spaces that are repeating before Test. My question is how to prevent ActionMailer (or anything else what is destroying my beautiful table) from doing that.

Mailer code:

  def remind(client, invoices)
    @client = client
    @company = @client.company
    @invoices  = invoices.to_a

    days_left = @invoices.first.pay_date - Date.today
    message = @client.group.messages.find_by_period days_left.to_i

    raise 'No messages for this invoices.' if message.nil?

    @template = message.template || if days_left < 0
      t 'message.before'
    elsif days_left > 0
      t 'message.after'
    else
      t 'message.today'
    end

    @text = liquid_parse @template
    @html = markdown_parse @text

    mail(:to => @client.email, :subject => t('message.title'))
  end

  private
    def markdown_parse(text)
      markdown = Redcarpet::Markdown.new Redcarpet::Render::HTML,
        :autolink => true, :space_after_headers => true
      markdown.render text
    end

    def liquid_parse(text)
      renderer = Liquid::Template.parse text
      renderer.render 'company' => @company, 'invoice' => @invoice, 'client' => @client
    end

Answer 1

I've found bug. It was caused by Premailer what I use to inline CSS in HTML part.

class InlineCSSInterceptor
  def self.delivering_email(message)
    #message.text_part.body = Premailer.new(message.text_part.body.to_s, with_html_string: true).to_plain_text # this is line causing the problem.
    message.html_part.body = Premailer.new(message.html_part.body.to_s, with_html_string: true).to_inline_css
  end
end

Mailer.register_interceptor InlineCSSInterceptor