Maildown

Markdown for your ActionMailer-generated emails.

Also due to the way it's implemented it extends markdown support for any other view you want to look for. It could be called markdown-rails or something, but this is what I named the gem and I'm sticking with it.

Maintenance policy

Follows the Rails maintenance policy https://guides.rubyonrails.org/maintenance_policy.html under "Severe Security Issues". Versions of Rails still under maintenance for Severe Security Issues should be expected to work with Maildown.

What?

• Fact: You should always send emails in text/html and text/plain at the same time
• Fact: Writing email body content twice sucks
• Fact: Markdown is amazing

So why not write your templates once in markdown, and have them translated to text and HTML? With Maildown now you can.

Install

Gemfile:

gem 'maildown'

Then run $ bundle install

Use

In your app/views/<mailer> directory create a file with a .md, .md+erb or .md.erb extension. When Rails renders the email, it will generate HTML by parsing the markdown, and generate plain text by sending the email as is.

Also if you skipped the part above, templates with these extensions can also be used outside of mail. For example you can have app/views/welcome/index.md.erb and it should work.

Verify Installation

Once you've got a file named .md.erb in your mailer directory, I recommend verifying the format in your browser in development using a tool such as mail_view. You can toggle between HTML and text at the top to make sure both look like you expect.

If you're going to style HTML emails, take a look at premailer-rails.

Upgrading to version 3.0

In 3.0 a lot of the internals were re-tooled to monkeypatch less so they behave more like what you would expect.

The Maildown::MarkdownEngine.set is deprecated and and has been removed. Instead, use Maildown::MarkdownEngine.set_html.

Layouts are now used by default. This setting is deprecated and does nothing:

Maildown.enable_layouts = true

There is no way to disable layouts via maildown, instead use normal Rails methods, such as moving to a mailer without a layout set.

Features

Different HTML/Text Layouts

In your mailer you can set a layout:

class UserMailer < ActionMailer::Base
  layout "mail_layout"

  # ...

Now when your render a markdown email it will look for layouts/mail_layout.html.erb and layouts/mail_layout.text.erb files.

Here's an example of a styled HTML layout

<% # layouts/mail_layout.html.erb %>
<%= stylesheet_link_tag "markdown.css" %>

<div class="readme">
  <article class="markdown-body">
    <%= yield %>
  </article>
</div>

You can leave the text version plain if you want, but don't forget to add a yield or it won't render

<%= yield %>

This does not currently work with format blocks in your mailer (AFAIK)

# THIS DOES NOT WORK
mail(to: user.email) do |format|
  format.html { render layout: 'my_layout' }
  format.text
end
# THIS DOES NOT WORK

If you need to have different layouts for different views I suggest you make a different mailer.

Indentation

In markdown when you indent your text it gets treated as a code block. This means if you're looping or branching in your markdown view, you cannot indent your code if you want it to show up fine. You end up writing code that looks like this:

<% if @write_docs.present? %>
## Write Docs

<% @write_docs.sort_by {|d| d.repo.full_name }.each do |doc| %>
**<%= doc.repo.full_name %>** ([source](<%= doc.to_github %>)): [<%= doc.path %>](<%= doc_method_url doc %>)

<% end %>
<% end %>

Gross.

To get around this, you can set this flag:

Maildown.allow_indentation = true

Now you can indent your code:

<% if @write_docs.present? %>
  ## Write Docs

  <% @write_docs.sort_by {|d| d.repo.full_name }.each do |doc| %>
    **<%= doc.repo.full_name %>** ([source](<%= doc.to_github %>)): [<%= doc.path %>](<%= doc_method_url doc %>)

  <% end %>
<% end %>

If you want to use a code block, you can use backticks instead of indentation:

```
This is a code block using backticks
```

This feature is hacky, and based off of removing whitespace before lines in your template (via regex 🙀).

Configure Markdown Renderer

Maildown uses kramdown by default. Kramdown is pure ruby, so it runs the same across all ruby implementations: jruby, rubinius, MRI, etc. You can configure another parser if you like using the Maildown::MarkdownEngine.set_html method and pasing it a block.

For example, if you wanted to use Redcarpet you could set it like this:

Maildown::MarkdownEngine.set_html do |text|
  carpet = Redcarpet::Markdown.new(Redcarpet::Render::HTML, {})
  carpet.render(text).html_safe
end

When maildown needs an HTML document the block will be called with the markdown text. The result should be HTML.

You can also customize the renderer for plain text. By default the text is passed through unmodified, but you may wish to use Kramdown to strip HTML tags, unify formatting etc.

Maildown::MarkdownEngine.set_text do |text|
  Kramdown::Document.new(text).tap(&:to_remove_html_tags).to_kramdown
end

Helpers in Markdown files

To get great looking emails in both HTML and plaintext, generate your own links like this:

[Your Profile](<%= user_url(@user) %>)

Instead of

<%= link_to "Your Profile", user_url(@user) %>

Bonus: it's shorter!

Future

This codebase depends on some metaprogramming to convince Action Mailer to render html and plain text from md. If you've got some ideas on how to add sane hooks into actionmailer to support this functionality more natively ping me @schneems.

Alternative Implementations

There is another project that accomplishes roughly the same thing by plataformatec: markerb.

Features we have that they don't:

• We support md, md+erb and md.erb file extensions. They only support markerb file extension.
• They require you manually add a block to each mailer with a text and HTML format, we don't.
• We allow you to strip templates with Maildown.allow_indentation.
• Their gem is unmaintained, but honestly it's pretty simple and will keep working for some time.
• We have way more monkeypatches than they do 🙀.

Test

We use the appraisal gem to generate Gemfiles. Install all dependencies with this:

$ bundle exec appraisal install

Get more info on other commands with:

$ bundle exec appraisal --help

Run a specific suite like this:

$ BUNDLE_GEMFILE=gemfiles/rails_7_0.gemfile bundle exec rake test

To add a new test case modify the Appraisals file in root and then re-run bundle exec appraisal install.

License

MIT