Commonmarker

Note This README refers to the behavior in the new 1.0.0.pre gem.

Ruby wrapper for Rust's comrak crate.

It passes all of the CommonMark test suite, and is therefore spec-complete. It also includes extensions to the CommonMark spec as documented in the GitHub Flavored Markdown spec, such as support for tables, strikethroughs, and autolinking.

For more information on available extensions, see the documentation below.

Installation

Add this line to your application's Gemfile:

gem 'commonmarker'

And then execute:

$ bundle

Or install it yourself as:

$ gem install commonmarker

Usage

Converting to HTML

Call to_html on a string to convert it to HTML:

require 'commonmarker'
Commonmarker.to_html('"Hi *there*"', options: {
    parse: { smart: true }
})
# <p>“Hi <em>there</em>”</p>\n

The second argument is optional--see below for more information.

Options and plugins

Options

Commonmarker accepts the same parse, render, and extensions options that comrak does, as a hash dictionary with symbol keys:

Commonmarker.to_html('"Hi *there*"', options:{
  parse: { smart: true },
  render: { hardbreaks: false}
})

Note that there is a distinction in comrak for "parse" options and "render" options, which are represented in the tables below.

Parse options

Name	Description	Default
`smart`	Punctuation (quotes, full-stops and hyphens) are converted into 'smart' punctuation.	`false`
`default_info_string`	The default info string for fenced code blocks.	`""`

Render options

Name	Description	Default
`hardbreaks`	Soft line breaks translate into hard line breaks.	`true`
`github_pre_lang`	GitHub-style `<pre lang="xyz">` is used for fenced code blocks with info tags.	`true`
`width`	The wrap column when outputting CommonMark.	`80`
`unsafe`	Allow rendering of raw HTML and potentially dangerous links.	`false`
`escape`	Escape raw HTML instead of clobbering it.	`false`

As well, there are several extensions which you can toggle in the same manner:

Commonmarker.to_html('"Hi *there*"', options: {
    extension: { footnotes: true, description_lists: true },
    render: { hardbreaks: false}
})

Extension options

Name	Description	Default
`strikethrough`	Enables the strikethrough extension from the GFM spec.	`true`
`tagfilter`	Enables the tagfilter extension from the GFM spec.	`true`
`table`	Enables the table extension from the GFM spec.	`true`
`autolink`	Enables the autolink extension from the GFM spec.	`true`
`tasklist`	Enables the task list extension from the GFM spec.	`true`
`superscript`	Enables the superscript Comrak extension.	`false`
`header_ids`	Enables the header IDs Comrak extension. from the GFM spec.	`""`
`footnotes`	Enables the footnotes extension per `cmark-gfm`.	`false`
`description_lists`	Enables the description lists extension.	`false`
`front_matter_delimiter`	Enables the front matter extension.	`""`
`shortcodes`	Enables the shortcodes extension.	`true`

For more information on these options, see the comrak documentation.

Plugins

In addition to the possibilities provided by generic CommonMark rendering, Commonmarker also supports plugins as a means of providing further niceties.

Syntax Highlighter Plugin

code = <<~CODE
  ```ruby
  def hello
  puts "hello"
  end
CODE

puts Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "InspiredGitHub" } })

# <pre style="background-color:#ffffff;" lang="ruby"><code>
# <span style="font-weight:bold;color:#a71d5d;">def </span><span style="font-weight:bold;color:#795da3;">hello
# </span><span style="color:#62a35c;">puts </span><span style="color:#183691;">&quot;hello&quot;
# </span><span style="font-weight:bold;color:#a71d5d;">end
# </span>
# </code></pre>

To disable this plugin, pass nil:

Commonmarker.to_html(code, plugins: { syntax_highlighter: nil })
# or
Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: nil } })

Available themes

Here's a list of available themes:

"base16-ocean.dark"
"base16-eighties.dark"
"base16-mocha.dark"
"base16-ocean.light"
"InspiredGitHub"
"Solarized (dark)"
"Solarized (light)"

Output formats

Commonmarker can currently only generate output in one format: HTML.

HTML

puts Commonmarker.to_html('*Hello* world!')

# <p><em>Hello</em> world!</p>

Developing locally

After cloning the repo:

script/bootstrap
bundle exec rake compile

If there were no errors, you're done! Otherwise, make sure to follow the comrak dependency instructions.

Benchmarks

Some rough benchmarks:

$ bundle exec rake benchmark

input size = 11064832 bytes

Warming up --------------------------------------
           redcarpet     2.000  i/100ms
commonmarker with to_html
                         1.000  i/100ms
            kramdown     1.000  i/100ms
Calculating -------------------------------------
           redcarpet     22.317  (± 4.5%) i/s -    112.000  in   5.036374s
commonmarker with to_html
                          5.815  (± 0.0%) i/s -     30.000  in   5.168869s
            kramdown      0.327  (± 0.0%) i/s -      2.000  in   6.121486s

Comparison:
           redcarpet:       22.3 i/s
commonmarker with to_html:        5.8 i/s - 3.84x  (± 0.00) slower
            kramdown:        0.3 i/s - 68.30x  (± 0.00) slower

okliv / commonmarker